The Senlan SBH series of high-voltage inverters utilize advanced multi-level unit series technology, which combines multiple low-voltage power units in series to achieve direct high-voltage input to high-voltage output conversion. Its core principles encompass several crucial components:
Phase-Shift Transformer: Employing a multi-secondary phase-shift design, this transformer converts grid high voltage into multiple low-voltage outputs for the power units. The phase-shift technology effectively reduces harmonic currents on the grid side, enhancing power quality.
Power Units: Each power unit functions as an independent PWM inverter, capable of outputting voltage waveforms of specific amplitude and frequency. When multiple power units are connected in series, they form a high-voltage output, enabling precise control over high-voltage motors.
Fiber-Optic Communication: High-speed and reliable communication between power units and the control cabinet is facilitated through fiber-optic cables, transmitting control signals and status information to ensure rapid system response and stability.
Main Control System: Located within the control cabinet, this system oversees the logical control and computational processing of the entire inverter system. By receiving external commands and internal feedback signals, it precisely regulates the power units.
II. Usage Method
Installation and Wiring:
Install the inverter in a dry, well-ventilated, dust-free environment, keeping it away from flammable and explosive materials.
Follow the manual’s guidelines for wiring the main and control circuits, ensuring accurate and secure connections, with special attention paid to high-voltage isolation.
Parameter Setting:
Utilize the human-machine interface (HMI) to configure the inverter’s various parameters, including motor settings, control modes, and protection configurations.
Adjust acceleration/deceleration times, V/F curves, and other parameters according to specific operating conditions to meet requirements.
Startup and Commissioning:
Under safe conditions, follow the manual’s steps to initiate a no-load test of the inverter.
Observe the inverter’s operational status and motor response, gradually fine-tuning parameters to achieve optimal performance.
III. Precautions
Safety Considerations:
Throughout installation, commissioning, and maintenance, ensure power is disconnected and warning signs are displayed to prevent electrocution.
Strictly prohibit opening cabinet doors or touching live high-voltage components while the inverter is operational.
Operators must undergo professional training, familiarizing themselves with operational procedures and safety precautions.
Environmental Requirements:
Verify the inverter’s installation environment complies with manual specifications, preventing damage from excessive temperature, humidity, or corrosive gases.
Regularly inspect and clean the inverter’s surroundings, ensuring proper ventilation.
Periodic Inspections:
Routinely check the inverter’s terminal blocks, capacitors, resistors, and other components for damage, promptly replacing worn parts.
Keep an eye out for abnormal vibrations, noises, or odors emanating from the inverter, addressing any issues promptly.
IV. Maintenance Precautions
Routine Maintenance:
Regularly verify the inverter’s operating environment, monitoring factors such as temperature and humidity.
Promptly attend to any unusual vibrations, sounds, or odors, investigating and resolving any issues encountered.
Schedule regular cleaning of fan filters and heat sinks to maintain optimal cooling performance.
Scheduled Servicing:
Conduct a comprehensive inspection and maintenance service every 3 to 6 months.
Securely tighten terminal blocks, swap out aging capacitors and resistors, and clean circuit boards and air ducts to prevent dust accumulation.
Professional Repairs:
For complex faults or specialized maintenance needs, promptly contact Senlan’s after-sales service team or qualified technicians. Avoid attempting unauthorized disassembly or repairs, which could exacerbate issues or pose safety hazards.
Centrifuges, as commonly used separation equipment in laboratories and industrial fields, rely heavily on stable and efficient rotational speed for optimal separation results and productivity. However, in practical applications, users may encounter issues where the centrifuge inverter operates at a sluggish pace, which not only affects separation effectiveness but also increases the risk of equipment failures. This article will analyze the reasons behind the slow speed of centrifuge inverters from multiple perspectives and provide corresponding solutions.
I. Reasons for Slow Speed of Centrifuge Inverter
Excessive Material Load When the amount of material being processed by the centrifuge exceeds its design capacity, the rotational speed naturally suffers, leading to sluggish acceleration. In such cases, reducing the material load is necessary to avoid overloading the centrifuge.
Accumulation of Impurities Inside the Centrifuge The interior of a centrifuge is prone to accumulating dust and other impurities, which can increase the rotational resistance of the rotor, thereby affecting the speed. Regular cleaning of the centrifuge to maintain equipment cleanliness is crucial to addressing this issue.
Damage to Rotor Bearings Damage to rotor bearings can not only cause a decrease in rotational speed but also lead to abnormal noises. Inspecting and replacing damaged rotor bearings can restore the centrifuge to its normal operating speed.
Loose or Worn Drive Belts Loose or worn drive belts are common causes of slow centrifuge speed. Regular inspection of belt tension and wear, along with timely replacement of damaged components, can ensure the proper functioning of the centrifuge.
Motor Failures Motor failures, such as winding circuit breaks, rotor fractures, or inverter malfunctions, directly impact the rotational speed of the centrifuge. In such situations, motor replacement or electrical circuit repairs are necessary.
Improper Inverter Parameter Settings As the key device controlling the centrifuge’s rotational speed, improper settings of the inverter parameters can also lead to sluggish speed. Checking and adjusting the inverter parameters to match the actual requirements of the centrifuge is essential.
Electrical Control System Malfunctions Issues with components in the electrical control system, such as adjustable resistors, thyristors, and rectifier diodes, can also cause unstable motor speed. Regular inspection of these components and timely replacement of damaged parts are important measures for maintaining the stability of the centrifuge’s electrical control system.
II. Solutions
Adjust Material Load Reasonably adjust the material load based on the centrifuge’s processing capacity to avoid overload operation.
Regularly Clean the Centrifuge Establish a regular cleaning schedule to ensure the centrifuge is free from impurity accumulation and remains clean.
Inspect and Replace Damaged Components Regularly inspect the condition of key components such as rotor bearings and drive belts, and promptly replace any damaged parts.
Adjust Inverter Parameters Adjust the inverter parameters according to the actual needs of the centrifuge to ensure stable rotational speed and compliance with process requirements.
Enhance Electrical Control System Maintenance Regularly inspect the condition of components in the electrical control system, such as adjustable resistors, thyristors, and rectifier diodes, and promptly repair or replace any damaged parts.
Professional Repair and Technical Support For complex fault issues, seek the assistance of professional repair personnel and technical support to ensure the centrifuge receives proper maintenance and repair.
III. Conclusion
The slow speed of a centrifuge inverter can be attributed to various factors, including excessive material load, accumulation of impurities inside the centrifuge, damage to rotor bearings, loose or worn drive belts, motor failures, improper inverter parameter settings, and electrical control system malfunctions. By implementing measures such as adjusting material load, regularly cleaning the equipment, promptly replacing damaged components, adjusting inverter parameters, and enhancing electrical control system maintenance, the issue of slow centrifuge inverter speed can be effectively resolved, thereby improving the operational efficiency and stability of the equipment. Additionally, for complex fault issues, seeking professional repair and technical support is essential.
The CDI-EM60 and EM61 series variable frequency drives (VFDs) from Hangzhou Delixi boast robust functionalities in industrial control applications. This article delves into the external terminal start and external potentiometer speed control features of these inverters, alongside an overview of their password security and fault code analysis capabilities.
I. External Terminal Start
The CDI-EM60 and EM61 series VFDs support versatile starting methods, including keypad control, terminal control, and communication control. External terminal start is a popular and flexible method, triggering the inverter’s start and stop through external signals.
Setup Steps for External Terminal Start:
Parameter Configuration:
Set the P0.0.03 (Operation Control Mode Selection) to 1 for terminal control.
Adjust other relevant parameters such as acceleration/deceleration times and frequency sources as needed.
Wiring:
Connect external control signals to the corresponding input terminals of the inverter (e.g., DI1, DI2).
Ensure compatibility between the external signal source (e.g., pushbuttons, relay contacts) and the inverter input terminals.
Testing:
Power on and test if the external control signals correctly trigger the inverter’s start and stop.
Fine-tune parameters for a smooth start-up process.
Precautions:
Ensure external control signals adhere to the inverter’s electrical specifications.
Regularly inspect wiring for secure connections to prevent control failures.
II. External Potentiometer Speed Control
External potentiometer speed control adjusts the inverter’s output frequency by rotating an external potentiometer, thereby regulating motor speed.
Setup Steps for External Potentiometer Speed Control:
Parameter Configuration:
Set the P0.0.04 (Frequency Source Selection) to 2 (Keypad Potentiometer) or 1 (External Terminal VF1, if connecting the potentiometer to VF1).
Adjust parameters like maximum frequency and acceleration time to suit speed control requirements.
Wiring:
Connect the wiper, fixed terminal, and variable terminal of the potentiometer to the corresponding inverter terminals (e.g., VF1, GND).
Ensure the potentiometer’s electrical specifications match the inverter’s input requirements.
Testing:
Rotate the potentiometer and observe if the inverter’s output frequency varies accordingly.
Adjust the potentiometer’s rotation range and inverter parameters for optimal speed control.
Precautions:
Regularly check potentiometer connections for reliability to prevent speed instability.
Avoid sudden disconnection or short-circuiting of potentiometer wiring during inverter operation.
III. Password Settings and Decoding
The Delixi inverters offer password protection to restrict unauthorized parameter modifications.
Password Setup:
Access the Password Menu:
Navigate through the inverter’s keypad to the parameter setting interface.
Locate the password-related function code (e.g., P5.0.20) and enter the password setup menu.
Enter the Password:
Input a custom 5-digit password.
Confirm the password and save changes before exiting the setup menu.
Password Decoding and Recovery:
Decoding: Enter the correct password to lift password protection and regain full inverter control.
Password Recovery: If forgotten, contact the inverter supplier or manufacturer for unlocking or password reset.
IV. Fault Code Analysis
During operation, the Delixi inverters may display fault codes indicating the device’s status and fault types.
Err01: Overcurrent During Constant Speed. Possible causes include output circuit shorts or load surges. Inspect and resolve issues before restarting the inverter.
Err02: Overcurrent During Acceleration. Might stem from motor/circuit shorts or inadequate acceleration time. Adjust parameters or check wiring.
Err04: Overvoltage During Constant Speed. Verify input voltage and bus voltage readings.
Err07: Module Fault. Could indicate inverter module damage, requiring replacement or professional service.
Err10: Motor Overload. Check for motor blockage or excessive loads, adjust motor protection parameters, or reduce the load.
Consulting the inverter manual’s fault code table enables swift troubleshooting and ensures uninterrupted production.
In conclusion, the CDI-EM60 and EM61 series VFDs from Hangzhou Delixi excel in industrial control with their versatile starting mechanisms, precise speed regulation, robust security features, and intuitive fault diagnosis. Mastering these functionalities optimizes device performance and enhances operational safety.
When using ABB’s ACS series inverters, including ACS180, ACS530, ACS580, and ACS880, users may encounter the FAULT 7086 alarm code, which is not explicitly mentioned in the manuals for these models. This article delves into the reasons behind this alarm and provides comprehensive solutions to help users quickly identify and resolve the issue.
Background of FAULT 7086 Alarm
Although the operation manuals for ACS180, ACS530, ACS580, and ACS880 do not directly mention FAULT 7086, the explanation for this alarm code is found in the ACS380 (specifically designed for crane applications) manual. FAULT 7086 indicates “AI Overvoltage in I/O Module,” meaning that an overvoltage has been detected at the analog input (AI) port.
Cause Analysis
AI Port Overvoltage: When the input voltage at the AI port exceeds the set upper limit (typically 10VDC or a configurable value such as 7.5VDC), the inverter triggers the FAULT 7086 alarm to protect internal circuits from damage.
AI Signal Mode Change: If the AI signal level exceeds the acceptable range, the inverter may attempt to automatically switch the AI to voltage mode. If this fails, it will trigger the alarm.
Circuit Board Component Issues: Although the circuit board designs of ACS180, ACS530, ACS580, and ACS880 differ, they share a core control system. Issues with the mainboard, drive board connections, or related components can also lead to unexpected FAULT 7086 alarms.
Solutions
1.Check AI Voltage:
（1）Use a multimeter to measure the actual input voltage at the AI port and confirm if it exceeds the set upper limit.
（2）Adjust the AI port’s voltage upper limit setting, if necessary, to suit the current operating 2.environment.
（1）Inspect External Connections:
Verify that the external signal source for the AI port is normal, with no abnormal fluctuations or damage.
（2）Check the connection cables and plugs for the AI port to ensure they are securely connected and free from looseness.
3.Examine Circuit Boards and Modules:
（1）If suspecting a circuit board or module failure, first inspect the cables and plugs between the mainboard and drive board, cleaning dust and ensuring good contact.
（2）If possible, try replacing suspected circuit boards or modules to verify if the issue is resolved.
4.Refer to Relevant Documentation:
（1）Although the ACS180, ACS530, ACS580, and ACS880 manuals do not directly mention FAULT 7086, refer to the ACS380 manual for more information on handling AI overvoltage.
（2）Contact our technical team for free technical consultation and assistance
5.Reset the Inverter:
After ruling out external hardware issues, attempt to reset the inverter to see if the alarm clears.
Conclusion
The FAULT 7086 alarm in ACS series inverters, including ACS180, ACS530, ACS580, and ACS880, can occur under specific circumstances not directly mentioned in their manuals. By thoroughly analyzing the alarm’s background and causes, and implementing appropriate solutions, users can effectively identify and resolve the issue. During the process, ensure safe operation and back up important data to prevent unexpected losses.
The TECO Inverter 7200GS, as a high-performance universal inverter, is widely used in industrial automation due to its support for various control modes including V/F control, Sensorless Vector Control, PID energy-saving control, and V/F+PG closed-loop control. This article will provide a detailed introduction to key operations of the TECO Inverter 7200GS, including panel startup, frequency speed regulation, password function setup and unlocking, as well as fault code analysis.
I. Panel Startup
1. Inspection and Preparation
Verify the Inverter Installation Environment: Check if the surrounding temperature, humidity, and ventilation conditions meet the requirements, ensuring no corrosive gases or dust.
Electrical Inspection: Ensure all electrical connections, particularly the input/output power supply and motor connections, are correct.
2. Power-On Startup
Connect the main power supply to the inverter. The “CHARGE” indicator light will illuminate, indicating that the internal capacitor is charging.
Once the “CHARGE” indicator light goes out, it means charging is complete, and the inverter is ready for operation.
3. Panel Operation
Use the standard LCD or LED operator panel to switch to the “DRIVE” mode.
Press the “RUN” button to start the inverter, and the motor will subsequently operate.
II. Panel-Set Frequency Speed Regulation
1. Enter Frequency Setting Mode
In the “DRIVE” mode, navigate to the frequency setting interface using the number keys and direction keys on the panel.
Use the direction keys to select the “Frequency Command” option and input the desired frequency value using the number keys.
2. Speed Regulation Operation
After entering the frequency value, press the “ENTER” key to confirm, and the inverter will adjust the motor speed according to the set frequency value.
Smooth speed regulation can be achieved by continuously changing the frequency value.
III. Password Function Setup and Unlocking
1. Password Setup
With the inverter stopped, enter the parameter setting mode through the panel.
Locate the parameter related to password setup (e.g., Sn-xx) and input the desired password value according to your needs.
Save the parameter settings and exit the setup mode after completing the password setup.
2. Password Unlocking
To unlock a set password protection, re-enter the parameter setting mode.
Input the correct password value, save, and exit the setup mode to remove the password protection.
IV. Fault Code Analysis
1. UV1 (Under Voltage)
Fault Description: The DC main circuit voltage is too low during operation.
Possible Causes: Insufficient power supply capacity, voltage drop in wiring, improper inverter power supply voltage selection, etc.
Countermeasures: Check the power supply voltage and wiring, verify the power supply capacity and system, install an AC reactor, etc.
2. OC (Over Current)
Fault Description: The inverter output current exceeds 200% of the rated current.
Possible Causes: Short acceleration time, short circuit or grounding at the output terminals, motor capacity exceeding the inverter capacity, etc.
Countermeasures: Extend the acceleration time, check the output terminal wiring, replace the inverter with an appropriate capacity, etc.
3. OL3 (Over Load)
Fault Description: Excessive output torque triggers the over-torque protection.
Possible Causes: Abnormal mechanical load, improper over-torque detection level settings, etc.
Countermeasures: Inspect the mechanical operation, set an appropriate over-torque detection level, etc.
4. PG0 (PG Disconnection)
Fault Description: Disconnection of the PG (encoder) signal.
Possible Causes: Poor contact or disconnection in the PG wiring.
Countermeasures: Check the PG wiring to ensure proper contact.
V. Conclusion
The TECO Inverter 7200GS, as a powerful inverter, offers flexible speed regulation, startup, and protection functions. Through this article, users can better understand and master key operations such as panel startup, frequency speed regulation, password settings, and fault code analysis, thereby enhancing equipment efficiency and stability. In practical applications, users should configure inverter parameters according to specific needs and environmental conditions to ensure proper operation.
The ACS530 series inverter from ABB, a leading player in industrial automation, is widely utilized across various industries. However, during operation, users may encounter various fault alarms, with fault code 2310 being a common one, indicating an overcurrent fault. Based on the provided documentation, this article delves into the causes and corresponding solutions for ABB Inverter ACS530 series alarm 2310.
I. Causes of Fault 2310
1. Excessive Motor Load
When the motor load exceeds its rated capacity, it can lead to a sharp increase in current, triggering the overcurrent protection. This may be due to an overly heavy load driven by the motor, mechanical jams, or motor stalls.
2. Incorrect Inverter Parameter Settings
The parameter settings of the inverter significantly impact its operational performance. Improper settings for acceleration time, deceleration time, or low current limits and overload protections can cause excessive current during motor startup or operation, resulting in an overcurrent alarm.
3. Unstable Power Supply Voltage
Fluctuations in power supply voltage directly affect the output voltage and current of the inverter. Unstable power supply can prevent the inverter from operating steadily, causing the output current to exceed normal ranges and trigger the overcurrent protection.
4. Motor or Cable Faults
Internal motor shorts, open windings, or grounding faults in motor cables can lead to excessive current. Additionally, contactors in the motor cable that are opening or closing can generate instantaneous high currents during switching, causing an overcurrent alarm.
5. Internal Inverter Faults
Damage or aging of internal components such as power modules, drive circuits, or current detection circuits in the inverter can result in unstable output currents, triggering an overcurrent alarm.
II. Solutions
1. Check Motor Load
First, inspect if the motor’s driven load is excessive. If so, attempt to reduce the load or replace the motor and inverter combination with higher capacities. Additionally, check for mechanical jams or stalls and address them promptly.
2. Review and Adjust Inverter Parameters
Examine the inverter’s parameter settings, particularly acceleration time, deceleration time, current limits, and overload protections. Ensure these settings are appropriate for the motor’s actual operational requirements. Adjust them if found to be incorrect.
3. Stabilize Power Supply Voltage
Use a multimeter or similar tools to check the stability of the power supply voltage. If significant fluctuations are present, implement measures to stabilize it, such as installing voltage stabilizers or UPS systems.
4. Inspect Motor and Cables
Examine the motor and motor cables for faults. Check for short circuits or open windings in the motor, verify the insulation resistance of the cables, and ensure no power factor correction capacitors or surge absorbers are present in the cables that could contribute to abnormal currents.
5. Check Internal Inverter Components
If all the above checks are normal, the overcurrent alarm may be due to internal inverter component damage. Contact professional technicians for inspection or replacement of faulty internal components.
III. Preventive Measures
To avoid the occurrence of ABB Inverter ACS530 series fault 2310, adopt the following preventive measures:
Regular Inspections and Maintenance: Conduct periodic inspections and maintenance of the motor and inverter to ensure their smooth operation.
Appropriate Parameter Settings: When setting inverter parameters, base them on the motor’s actual conditions to prevent incorrect settings from causing overcurrent faults.
Stable Power Supply Voltage: Maintain stable power supply voltage to prevent its fluctuations from affecting the inverter’s performance.
Suitable Motor and Inverter Selection: Choose motors and inverters that match the actual load requirements to prevent overcurrent faults due to excessive loads.
In conclusion, ABB Inverter ACS530 series fault 2310 is a critical fault alarm that requires attention. By thoroughly examining motor loads, adjusting inverter parameters, stabilizing power supply voltage, inspecting motors and cables, and checking internal inverter components, this issue can be effectively resolved, ensuring the inverter’s smooth operation. Furthermore, implementing preventive measures can reduce the likelihood of overcurrent faults and enhance the reliability and stability of the equipment.
The ABB ACS880 series inverters are widely used in industrial applications due to their high performance and reliability. However, issues can arise, especially when driving high-power motors. One such challenging fault is **Fault 2340**, which is related to motor cable or motor short circuits and IGBT module malfunctions. This article will analyze the potential causes of Fault 2340 and provide a troubleshooting guide to resolve it.
1. Fault Symptoms
In a real-world scenario, an ABB ACS880 inverter was used in a common DC bus system to drive a 1150HP motor. During startup, Fault 2340 occurred intermittently—about two to three times out of ten attempts. After thorough inspection, the motor insulation was found to be normal, ruling out motor and motor cable issues as the root cause.
2. Analysis of Causes for Fault 2340
(1)Motor Cable Insulation Issues: While the motor insulation was normal in this case, it’s essential to consider the possibility of phase-to-phase or phase-to-ground insulation issues in the motor cables, which could lead to Fault 2340. Though this is less likely, it should not be overlooked during troubleshooting.
(2)IGBT Module and Gate Driver Board Issues: The IGBT module is a critical component in the inverter. Faulty signals from the gate driver board of the IGBT module are a common cause of Fault 2340. This issue has a high probability and often requires replacing the IGBT module to resolve.
(3)Connection Issues Between IGBT Module and Interface Board**: If the ribbon cables connecting the IGBT module to the interface board are damaged or have high resistance, Fault 2340 may occur. This issue is moderately probable and should be addressed by thoroughly inspecting the connections.
(4)Interface Board Fault**: The interface board transmits control signals to the IGBT module. A malfunctioning interface board can also trigger Fault 2340. This issue is moderately likely and should be considered if other checks do not resolve the fault.
1. Fault Symptoms
In a real-world scenario, an ABB ACS880 inverter was used in a common DC bus system to drive a 1150HP motor. During startup, Fault 2340 occurred intermittently—about two to three times out of ten attempts. After thorough inspection, the motor insulation was found to be normal, ruling out motor and motor cable issues as the root cause.
2. Analysis of Causes for Fault 2340
(1)Motor Cable Insulation Issues: While the motor insulation was normal in this case, it’s essential to consider the possibility of phase-to-phase or phase-to-ground insulation issues in the motor cables, which could lead to Fault 2340. Though this is less likely, it should not be overlooked during troubleshooting.
(2)IGBT Module and Gate Driver Board Issues: The IGBT module is a critical component in the inverter. Faulty signals from the gate driver board of the IGBT module are a common cause of Fault 2340. This issue has a high probability and often requires replacing the IGBT module to resolve.
(3)Connection Issues Between IGBT Module and Interface Board**: If the ribbon cables connecting the IGBT module to the interface board are damaged or have high resistance, Fault 2340 may occur. This issue is moderately probable and should be addressed by thoroughly inspecting the connections.
(4)Interface Board Fault**: The interface board transmits control signals to the IGBT module. A malfunctioning interface board can also trigger Fault 2340. This issue is moderately likely and should be considered if other checks do not resolve the fault.
(1)Initial Inspection**:
– Use a multimeter to measure the diode characteristics between the inverter output terminals (U, V, W) and the DC bus terminals (R+, R-) to ensure they match expected values.
– Perform an insulation test on the motor and its cables to confirm there are no short circuits or grounding issues.
– Inspect the inverter for signs of moisture, condensation, or burn marks.
(2)Component Replacement**:
– If initial inspections reveal no issues, consider replacing the AINT board (interface board) to see if the fault is resolved.
– If the fault persists, disassemble the inverter and replace the IGBT module. During this process, carefully inspect all connections to ensure there are no loose or broken wires.
(3)Further Diagnosis**:
– If replacing the IGBT module and interface board does not resolve the issue, check and replace the current sensors and brake chopper IGBT.
– Throughout the process, handle all components with care, especially during reassembly, to prevent introducing new issues, such as poor connections or short circuits.
4. Conclusion
Fault 2340 in the ABB ACS880 inverter is a complex issue with multiple potential causes, ranging from motor cable insulation problems to IGBT module failures. Effective troubleshooting requires a thorough understanding of the inverter’s components and a methodical approach to diagnosing and repairing the fault. By following the steps outlined in this guide, technicians can systematically address and resolve Fault 2340, ensuring the reliable operation of the inverter.
The user went to a hardware and electrical store to buy a thermometer for automatic temperature control of the material tank in the production workshop. The control requirements put forward by the user are: when the temperature of the material tank is as low as 25 º C, start the boiler fan to heat it up; when the temperature of the material tank rises to 32 º C, stop the fan. The temperature is not required to be precisely controlled at one point, but it can be roughly maintained between 25 º C and 32 º C. In this way, the fan does not need to be started frequently and run for a long time, and the power saving effect will be very good. It is said that after searching several electrical and mechanical stores, no suitable temperature control meter can be found. If it can be solved here, it doesn’t matter if the price is a little higher, and five or six units can be purchased at once.
The father and son run the hardware and electrical store. The father is an old electrician, and the son is a student of the Department of Mechanical and Electrical Engineering, with top grades. The father and son were excited and decided to make this deal. The temperature controllers in the store generally have the following functions, see the wiring diagram below:
Figure 1: Temperature control meter wiring and three sets of contact output status diagram
From the wiring diagram, the temperature controller has three groups of output control contacts. KA0 is the control temperature output. If its normally closed point is used as the control output, the contact closing and opening action area is near the temperature setting point. For example, if the setting point is 25 º C, when the measured temperature rises to 25 º C, the normally closed contact is disconnected, and when the measured temperature drops to 23 º C, the contact is closed. This control method belongs to “point” control. The action of the relay tracks a temperature setting point. Although in order to avoid frequent switching at one point, there is often a temperature hysteresis value in the middle, such as 2 º C between 23 º C and 25 º C. Some models have this hysteresis fixed, while others are adjustable, but the temperature difference adjustment range is not too large. Obviously, the control output contact of KA0 cannot meet the control requirements put forward by users.
Let’s look at the output contact of KA1, which is the lower limit control output. It is also output based on a “temperature point”. When the measured temperature reaches the preset lower limit, KA1 will act. As long as it is within the lower limit, KA1 will maintain the output. Only when the measured temperature is higher than the lower limit setting point, KA1 will lose power and the contact will be released. The control requirements cannot be achieved by relying solely on the control contacts of KA1. The output contact of KA2 is the upper limit setting point. Its control principle is the same as that of KA1. It can also be regarded as a “point” control and cannot complete the control task independently.
My son suddenly had an idea: Is it possible to combine the lower limit and upper limit control outputs to meet the control requirements proposed by the user?
Dad nodded approvingly: Okay, I thought so too, let’s try to analyze it.
See the following control state diagram of KA1 and KA2 output combination and user control requirement diagram:
Figure 2: Upper and lower limit control states and user required control characteristic diagram
My son said: By connecting the normally closed points of the two relays KA1 and KA2 in series, the fan can be powered on and operated in the area where the two relays are not operating. That is, the fans in sections a and b in the figure can be powered on and operated. Doesn’t this meet the requirements?
Dad said: It seems not to work. The fan is also powered in sections c and d. The fan is powered and running most of the time. The fan stops only when it is outside the upper and lower limits. It still doesn’t work to use the two contacts directly. The user’s requirements are shown in the right figure of Figure 2. Only the thick line segments (a, b/1a, 1b) in the right figure are the time for the fan to run. When the detected temperature reaches the lower limit, the fan runs, and when it reaches the upper limit, the fan stops; then the temperature drops and reaches the lower limit again, the fan starts running again. The fan does not run at one “point”, but only runs on “segments” a and b, achieving a good power saving effect.
My son said: I didn’t notice the c and d segments in the left figure. It’s not possible. But we can use the upper and lower limit contact outputs and add an external control circuit to achieve it. This additional circuit should not be difficult to make.
The father wanted to test his son’s level, so he said: How about this, let’s both make an external control circuit, and see who’s circuit is simpler and more reasonable, and then we’ll use their circuit, okay?
The son knew that his father wanted to test his ability and it was also a small challenge for him. He thought that since he had worked on some complicated electromechanical control circuits, this small circuit should be no problem for him. So he readily agreed.
It seems to be a simple thing to think about, but in practice, this small function is not so easy to achieve. It seems that it cannot be completed with two additional relays, and the circuit is too complicated to use three relays. According to my father’s idea, it should be possible to achieve it with two additional relays. It seems that it cannot complete the task if one contact of KA1 and KA2 is used.
The son spent half a day drawing several diagrams, optimizing and simplifying the circuit, and finally succeeded through wiring tests. However, the analysis from the control principle was a bit confusing. The father frowned and thought about it at first, but suddenly grabbed a pen and drew a wiring diagram in no time. Without wiring tests, he announced that the circuit would definitely work.
The control circuit diagram made by the father and son is as follows:
In the figure, KA1 and KA2 are the upper and lower limit signal output relays inside the temperature control meter, KA3 and KA4 are external relays, and KA3 provides control signal output. The control circuit designed by my son uses the normally open and normally closed contacts of the upper limit relay, the normally closed contacts of the lower limit relay, and two sets of contacts of KA4. The control process is as follows: After the equipment is powered on, the normally closed contact circuit of KA2 and KA4 provides power to the KA3 coil, KA3 is energized, the fan runs, and the discharge tank begins to heat up; when the temperature reaches the upper limit, the normally closed point of KA2 is disconnected, the normally open point is connected, KA3 loses power, and at the same time KA4 is energized for self-protection, the fan stops, and the discharge tank begins to cool down; due to the self-protection effect of KA4, when the temperature drops below the upper limit, KA4 maintains an energized state through the normally closed point of KA1 and its own self-protection contact, and KA3 maintains a de-energized state, and the temperature of the discharge tank continues to drop until it reaches the lower limit of the temperature, the KA1 lower limit relay is activated, the KA4 self-protection circuit is disconnected, KA4 loses power, KA3 is energized again, and the fan runs.
The control circuit designed by my father seems to be simpler. The circuit is clear in principle and is more convenient for analyzing the control process: when the temperature of the unloading tank reaches the lower limit, KA3 is energized and forms a self-protection (self-locking) circuit through the normally closed point of KA4 and the normally open point of KA3, and the fan runs; when the temperature reaches the upper limit, the normally open point of the upper limit relay KA2 is connected, KA4 is energized, and while disconnecting the self-locking circuit of KA3, it forms its own self-locking circuit through the normally closed point of KA3 and the normally open point of KA3. KA4 remains energized, KA3 remains de-energized, and the fan stops; when the temperature drops to the lower limit of the temperature, the relay KA1 is activated, KA3 is activated, and while disconnecting the self-locking circuit of KA4, KA3 forms its own self-locking circuit, and the fan starts running again.
The focus of control requirements is to meet two conditions:
1. Once KA3 and KA4 are powered, they can be self-protected (self-locked);
2. When two relays are powered on for self-protection, the self-protection circuit of relay B must be disconnected to make it lose power. The same is true in reverse.
This control method is not conventional temperature point control, but temperature range control, which can be regarded as a special application.
Both the son’s and the father’s circuits can accomplish the task, and use the same number of contacts, but the father’s circuit is easier to understand and more classic. The son’s circuit also accomplishes the task well, which is rare.
Dad said: I thought of these two conditions, and based on these conditions, I formed this circuit in the computer. It was a waste of effort before the logical relationship of the circuit was clear.
Although the son has figured out the circuit, it seems that his father is still better in terms of circuit routing and principle analysis. His father’s circuit is more “smooth”, while my own circuit is a bit tortuous. When you make a circuit yourself, you should be better at analyzing the logical relationship and take a “smooth” path to make the circuit more optimized and reasonable.
The fan control wiring diagram is as follows:
In the figure, KA1 and KA2 are the upper and lower limit signal output relays inside the temperature control meter, KA3 and KA4 are external relays, and KA3 provides control signal output. The control circuit designed by my son uses the normally open and normally closed contacts of the upper limit relay, the normally closed contacts of the lower limit relay, and two sets of contacts of KA4. The control process is as follows: After the equipment is powered on, the normally closed contact circuit of KA2 and KA4 provides power to the KA3 coil, KA3 is energized, the fan runs, and the discharge tank begins to heat up; when the temperature reaches the upper limit, the normally closed point of KA2 is disconnected, the normally open point is connected, KA3 loses power, and at the same time KA4 is energized for self-protection, the fan stops, and the discharge tank begins to cool down; due to the self-protection effect of KA4, when the temperature drops below the upper limit, KA4 maintains an energized state through the normally closed point of KA1 and its own self-protection contact, and KA3 maintains a de-energized state, and the temperature of the discharge tank continues to drop until it reaches the lower limit of the temperature, the KA1 lower limit relay is activated, the KA4 self-protection circuit is disconnected, KA4 loses power, KA3 is energized again, and the fan runs.
The control circuit designed by my father seems to be simpler. The circuit is clear in principle and is more convenient for analyzing the control process: when the temperature of the unloading tank reaches the lower limit, KA3 is energized and forms a self-protection (self-locking) circuit through the normally closed point of KA4 and the normally open point of KA3, and the fan runs; when the temperature reaches the upper limit, the normally open point of the upper limit relay KA2 is connected, KA4 is energized, and while disconnecting the self-locking circuit of KA3, it forms its own self-locking circuit through the normally closed point of KA3 and the normally open point of KA3. KA4 remains energized, KA3 remains de-energized, and the fan stops; when the temperature drops to the lower limit of the temperature, the relay KA1 is activated, KA3 is activated, and while disconnecting the self-locking circuit of KA4, KA3 forms its own self-locking circuit, and the fan starts running again.
The focus of control requirements is to meet two conditions:
1. Once KA3 and KA4 are powered, they can be self-protected (self-locked);
2. When two relays are powered on for self-protection, the self-protection circuit of relay B must be disconnected to make it lose power. The same is true in reverse.
This control method is not conventional temperature point control, but temperature range control, which can be regarded as a special application.
Both the son’s and the father’s circuits can accomplish the task, and use the same number of contacts, but the father’s circuit is easier to understand and more classic. The son’s circuit also accomplishes the task well, which is rare.
Dad said: I thought of these two conditions, and based on these conditions, I formed this circuit in the computer. It was a waste of effort before the logical relationship of the circuit was clear.
Although the son has figured out the circuit, it seems that his father is still better in terms of circuit routing and principle analysis. His father’s circuit is more “smooth”, while my own circuit is a bit tortuous. When you make a circuit yourself, you should be better at analyzing the logical relationship and take a “smooth” path to make the circuit more optimized and reasonable.
The main circuit of the inverter is a voltage-type, AC-DC energy conversion inverter. Since there is a large-capacity capacitor energy storage circuit between the rectifier and inverter circuits, and the voltage across the capacitor cannot change suddenly, in the initial power-on stage, the capacitor device is equivalent to a “short circuit”, which will form a huge surge charging current, which will cause a large current impact on the rectifier module and cause it to be damaged, and will also cause the air circuit breaker connected to the inverter power supply end to trip due to overcurrent.
The conventional processing method is to connect a current limiting resistor and a charging contactor (relay) in series between the rectifier and the capacitor energy storage circuit. The control of the capacitor charging process is as follows:
When the inverter is powered on, the charging resistor first limits the current of the capacitor to suppress the maximum charging current. As the charging process extends, the charging voltage gradually builds up on the capacitor. When the voltage amplitude reaches about 80% of 530V, two control processes occur. One is that the switching power supply circuit of the inverter starts to oscillate. The 24V output of the switching power supply directly drives the charging relay, or the relay connects the coil power supply circuit of the charging contactor. The charging contactor (relay) is closed. When the charging current limiting resistor is short-circuited, the inverter enters the standby working state. After a certain voltage is established on the capacitor, its charging current amplitude is greatly reduced, and the closing/switching current of the charging contactor is not too large. After that, the power supply of the energy storage capacitor circuit and the inverter circuit is supplied by the closed contactor contacts, and the charging resistor is short-circuited by the normally open contact of the contactor. The second is that as the charging voltage on the capacitor is established, the switching power supply starts to oscillate, and the CPU detects the voltage amplitude signal sent by the DC circuit voltage detection circuit, determines that the charging process of the energy storage capacitor has been completed, and outputs a charging contactor action instruction. The charging contactor is powered on and closed, and the capacitor charging process ends.
The common main circuit forms of the inverter and the charging contactor control circuit are shown in the figure below:
Figure 1: Common types of inverter main circuits
Figure 2: Control circuit of charging contactor
For some inverters and high-power inverters, the rectifier circuit often adopts a three-phase half-controlled bridge circuit, that is, the lower three arms of the three-phase rectifier bridge are rectifier diodes, and the upper three arms use three unidirectional thyristors, using thyristors as “contactless switches” to replace charging contactors. This saves installation space and improves circuit reliability. The circuit form is shown in the figure below:
Figure 3: Control circuit of charging contactor
Although the charging contactor is omitted, the working principle is the same, but the control circuit is different. During the power-on period of the inverter, D1 ∽ D6 is used for rectification, and R is used for current limiting to charge C1 and C2. When the charging process is close to the end, the CPU outputs the opening instruction of the three thyristors SCR1 ∽ SCR3, and the control circuit forces the three thyristors to conduct. The power-on pre-charging circuit composed of D1, D2, D3, and R is used. SCR1 ∽ SCR3 and D4, D5, and D6 form a three-phase rectifier bridge. At this time, the thyristor is in a fully conductive state, which is equivalent to a rectifier diode.
The opening of the thyristor requires two conditions: 1. The positive voltage between the anode and the cathode; 2. A trigger current loop is formed between K and G. The circuit is connected to the three terminals of the AC input power supply to provide unidirectional controlled rectification. During the three positive half-wave voltages of the three-phase AC power, if the trigger current is formed at the same time, the three thyristors can be opened. The first condition has been formed naturally, and the second condition is sufficient to control its opening.
To put it simply, as long as a trigger current (pulse or DC) is provided to the thyristor during the period when the thyristor is subjected to a forward voltage – when the AC voltage passes through zero, the thyristor can be turned on well during the positive half-wave of the AC power and rectify the input AC voltage (just like a diode). The simplest trigger circuit is to introduce a resistor from the anode to the G pole, and during the positive half-wave of the AC power (after the zero point), the trigger current is synchronously introduced to the thyristor to turn on the thyristor. For example, the main circuit form of Dongyuan 300kW inverter is the same as Figure 3, and the trigger circuit is relatively simple:
Figure 4: SCR trigger control circuit 1
Figure 4 is one of the thyristor trigger circuits. The other two trigger circuits are the same. The components R45, C30, C31 and other components connected in parallel at the anode and cathode of the two thyristors are peak voltage absorption networks to provide overvoltage protection for the thyristors. The KA2 contact, D15, R44, and 24R form a trigger current path. The function of D15 is to rectify the input voltage half-wave to prevent the thyristors G and K from being subjected to the impact of reverse trigger voltage/current. R44 and 24R are current limiting resistors to limit the peak trigger current and protect the safety of the thyristors. R43 is a noise elimination resistor to increase the reliability of the thyristor operation.
When the CPU issues a thyristor on command, relay KA2 is powered on and closed, a positive half-wave voltage is input, rectified by D15, limited by R44 and 24R, flows into the G pole of the thyristor, and flows out from the K pole, forming a trigger current path, and the thyristor is turned on. The thyristor in the circuit is not in the voltage regulation working area, the conduction angle is the largest, and it is in the “full conduction state”, just like a switch device, only in the two states of conduction and cutoff, without the third state of phase shift (voltage regulation). This is where attention needs to be paid. Therefore, the control circuit is different from the conventional phase shift control circuit and is relatively simple.
A slightly more complex thyristor control circuit, such as the trigger circuit of the Delta 37kW inverter thyristor, is shown in the figure below:
Figure 5: SCR trigger control circuit 2
After rectification and filtering by an independent power supply winding of the switching power supply, it is used as the power supply for the thyristor trigger circuit. The control circuit consists of the NE555 time base circuit, the DPH2, DQ22, DQ3 trigger pulse on/off circuit, and the D and R three-way trigger flow circuit. After the switching power supply works, the NE555 time base circuit is connected to a multi-resonance oscillator and is powered on. Whether the oscillation pulse output from pin 3 is sent to the three trigger circuits of the subsequent stage depends on the command control of the CPU. The command signal of the CPU is introduced to the input side of the photocoupler DPH2 through the 24th pin of the control wiring terminal DJ8. When the transistor on the output side of the optocoupler is turned on, the pulse signal of the NE555 oscillator is sent to the D and R trigger circuit loop of the subsequent stage through the transistors DQ22 and DQ3. After the CPU issues the thyristor opening command, the three devices DPH2, DQ22, and DQ3 are always in the on state, and the trigger pulse is always added to the G and K of the three thyristors. The peak trigger current is about 100mA.
In addition, in the Panasonic and Fuji small power inverter models, another form of main circuit structure is used to complete the initial charging control of the main circuit capacitor. This is the internal circuit structure diagram of the 7MBR35SD120 integrated power module. The circuit is shown in Figure 6:
The difference of the circuit is that a controllable device is added after the three-phase rectifier bridge. A charging resistor must be connected in parallel to the terminals 21 and 26. After a certain charging voltage is established on the main circuit capacitor, a trigger current is input from terminals 25 and 26, then the thyristor is turned on and the inverter enters the standby working state.
The control circuit is generally powered by an independent 24V winding of the switching transformer to obtain control power with a “floating ground”. The control circuit is mostly an oscillation circuit, which increases the pulse trigger current of the thyristor device. The oscillation circuit is not a conventional phase-shift trigger circuit, but provides high-frequency/density random trigger pulses to put the thyristor in a fully conductive state. The thyristor here, under the action of high-density trigger impulses, is like a switch “turned to the on position”. There is no actual surveying circuit on hand for the trigger circuit of this model, so we can only draw a simple diagram based on the circuit structure for reference.
Figure 6: 7MBR35SD120 integrated power module
Figure 7: thyristor trigger circuit of 7MBR35SD120S module
A factory has a 5.5 kW submersible pump. To facilitate water volume adjustment and energy-saving operation, an electrician proposed using a VFD to drive the pump.
The task was taken on by Mr. Zhang, a friend of the electrician. For safety, Mr. Zhang selected a 7.5 kW VFD from a reputable brand. This brand’s VFDs are widely used in various industries such as plastics, chemicals, and wood processing without significant issues, indicating decent quality. The VFD control box was installed in the boiler room, with power sourced from the workshop distribution panel. The three-phase voltage balance was excellent, maintaining within 380V ±5%. During the trial run, the VFD did not need to operate at full speed, running around 30Hz with the working current at half of the VFD’s rated current. Mr. Zhang was confident that the VFD would operate safely for a long time.
However, three days later, the factory’s electrician called Mr. Zhang, reporting that the VFD had stopped, and the control panel was unresponsive, indicating no power. Surprised, Mr. Zhang visited the site and confirmed the issue. Assuming a quality problem with the VFD, he replaced it with another 7.5 kW VFD from the supplier and sent the defective one for repair.
This time, the VFD failed after just a day and a half. Frustrated, Mr. Zhang called the supplier to complain and replaced the VFD with another brand. He again checked the operating voltage and current, which were similar to the initial installation, indicating no issues with the pump or power supply. Mr. Zhang concluded that the first batch of VFDs might have had quality defects and hoped the new brand would solve the problem.
Unexpectedly, the newly installed VFD also failed within hours, with the factory’s electrician calling Mr. Zhang again. The recurring issue led to reprimands from the factory boss to the electrician, who then passed the blame to Mr. Zhang. Baffled, Mr. Zhang inspected the three faulty VFDs. He found that two had open circuits between the R and P1 (external brake resistor terminal), possibly due to damaged charging resistors, which indicated rectifier circuit issues. The third VFD had a short circuit between R and S, suggesting a failed rectifier module. However, the inverter modules in all three VFDs were intact. The damages seemed to result from power surges, not load-related issues, as the three-phase supply voltage and input current were normal. Having worked with VFDs for several years, Mr. Zhang found this problem unprecedented.
In desperation, Mr. Zhang called his friend, electrician Mr. Li, for advice. Mr. Li suggested installing a three-phase input reactor before the VFD’s power terminals to solve the problem.
Mr. Zhang inquired about the cause of the failures. Mr. Li explained three potential reasons related to the power supply:
1. The submersible pump continued to operate after work hours for employee showers, meaning a 630 kVA transformer supplied a 7.5 kW VFD, causing a significant capacity disparity. The VFD’s input current contained high harmonic components, generating large rectifier inrush currents that damaged the rectifier module and charging resistor during startup.
2. The workshop distribution panel might have parallel capacitor compensation cabinets. The start and stop of large motors (above 100 kW) and the switching currents of capacitors created harmful voltage spikes and inrush currents, impacting the VFD.
3. The same power line might have other large VFDs, soft starters, or DC speed controllers. The nonlinear rectifier currents from these devices severely distorted the power supply waveform, increasing harmful harmonics and deteriorating power quality.
Mr. Li noted that input reactors, often depicted in VFD wiring diagrams, are frequently omitted during installation to save costs, leading to such issues.
Mr. Zhang didn’t have ready-made three-phase reactors and needed an immediate solution. Mr. Li suggested using XD1 series chokes from old capacitor compensation cabinets as reactors, which could suppress inrush currents effectively. Mr. Zhang contacted several suppliers but learned that most manufacturers had stopped producing these chokes.
Under pressure, Mr. Zhang reached out to Mr. Li again, demanding a solution. Mr. Li, while having lunch, suggested using current transformers (CTs), which Mr. Zhang likely had. Any CT, regardless of size, with a rated current of 5A, could be used. CTs with more winding turns (e.g., 50/5) would offer better inrush current suppression and filtering but might have a higher voltage drop. Conversely, CTs with fewer turns (e.g., 250/5) would have a smaller voltage drop but less effective smoothing. Depending on the VFD’s rated current, Mr. Li recommended using three CTs per phase or two if the running current was around 7A. CTs would provide better inductance and performance than XD1 chokes.
After installing CT-based “input reactors,” the VFD’s input current became stable, reducing harmonics and voltage spikes, ensuring safer operation.
Months later, Mr. Zhang checked with the factory electrician, who confirmed that the VFD had been operating normally. Mr. Zhang realized the VFD failures were due to power supply issues, not the VFD quality. He felt vindicated and teased the electrician about owing him a drink for resolving the issue.
