Category: Other Drives

Posted on by — Leave a comment

Reasons for Slow Speed of Centrifuge Inverter and Solutions

Centrifuge frequency converter control cabinet

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

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
Centrifuge and control system

II. Solutions

  1. Adjust Material Load
    Reasonably adjust the material load based on the centrifuge’s processing capacity to avoid overload operation.
  2. Regularly Clean the Centrifuge
    Establish a regular cleaning schedule to ensure the centrifuge is free from impurity accumulation and remains clean.
  3. 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.
  4. 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.
  5. 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.
  6. 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.

Posted on by — Leave a comment

External Terminal Start & Potentiometer Speed Control with Password Security and Fault Code Analysis on CDI-EM60 and EM61 Series Inverters from Hangzhou Delixi

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

Pictures of Hangzhou Delixi CDI-EM60 and EM61 series drivers

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:

  1. 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.
  2. 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.
  3. 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.
Delixi VFD CDI-EM60 and EM61 External Terminal Control Wiring Diagram

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:

  1. 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.
  2. 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.
  3. 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:

  1. 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.
  2. 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.

Posted on by — Leave a comment

Operation Guide and Fault Code Analysis of TECO Inverter 7200GS

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.

TECO inverter image

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.

Posted on by — Leave a comment

Converting 0-10VDC to 4-20mA for Robust Signal Transmission in Water Supply Systems

In variable frequency water supply control systems, remote pressure gauges play a crucial role in monitoring and maintaining consistent pressure levels. These gauges often exhibit resistance values ranging from 100 to 500 ohms, which correspond to a continuous pressure range, such as 0-10 MPa. Traditionally, this variable resistance can be utilized by series connecting a larger resistor and applying a 0-10V signal. This setup produces a continuously varying voltage that is suitable for frequency converters, PLCs, and other control devices. However, in practical engineering applications, 4-20mA signals are preferred over 0-10V due to their enhanced resistance to interference. Consequently, converting resistance or voltage signals into 4-20mA signals becomes essential for reliable transmission and control.

To address this need, several frequency converter manufacturers have developed specialized water supply signal acquisition boards. These boards are not limited to constant pressure water supply systems and can be applied across various industrial scenarios. Below, we explore three conversion circuits that serve as valuable learning resources and references.

One notable solution is a water supply substrate R/I conversion circuit board designed by a leading frequency converter manufacturer. This board effectively transforms the resistance changes from a remote pressure gauge into a 4-20mA current signal, which is then fed into the control terminal. By comparing this signal with a预设 pressure value, the frequency converter automatically adjusts its output frequency to ensure constant pressure in the water supply network.

The 4-20mA signal source circuit essentially functions as a constant current source with high internal resistance. The output current remains consistent, regardless of the external load resistance. Within this circuit, T2 and T3 form two constant current source circuits: T2 acts as a “fixed” constant current source, while T3 operates as a “variable” one.

The circuit is powered by a 12V DC voltage from the CPU motherboard, which undergoes isolation and filtering through D1 and C4 before reaching the Vcc1 water supply substrate. Further processing by R1 and TL431 converts Vcc1 into a 2.5V reference voltage. This voltage is then used in conjunction with the TL431, operational amplifier circuit (comprising R2, Z2, and the internal resistance of the remote pressure gauge), and the T2 circuit to create a constant current circuit of approximately 4.9 mA.

The resistance changes in the remote pressure gauge are translated into voltage variations across the Z2 resistor. This pressure signal is subsequently input into the second-stage operational amplifier circuit (pins 5 and 6) via R3. The T3 circuit forms the “variable” constant current source, where changes in the gauge’s internal resistance are converted into signal voltage inputs for the operational amplifier. This stage, with deep negative feedback (an amplification factor of 1), maintains a constant current source circuit. The output current is directly dependent on the gauge’s internal resistance.

For enhanced protection, Z1 and Z3 are voltage-embedded protection diodes at the signal input and output terminals. Typically, the internal resistance of the frequency converter’s current input terminals is 250 ohms.

Alternatively, dedicated signal conversion chips, such as the AD694, simplify the conversion process. These chips require only a current-limiting resistor and a transistor to accurately convert 0-10V signals to 4-20mA. With the control terminal of the frequency converter powered by a 24V supply, these chips offer excellent anti-interference performance.

A third option involves constructing a 0-10V/4-20mA signal conversion circuit using an operational amplifier circuit and discrete components. However, this approach necessitates two power supplies and initial output current adjustments, making it less practical and less commonly used.

In conclusion, converting 0-10VDC to 4-20mA signals is crucial for ensuring robust and interference-resistant transmission in water supply control systems. The described circuits and solutions provide effective means of achieving this conversion, catering to various industrial applications and requirements.

Posted on by — Leave a comment

Understanding and Repairing Brake Units in Frequency Converters

In the realm of industrial machinery, frequency converters play a crucial role in controlling motor speed and efficiency. However, when dealing with high inertia loads, such as in mining elevators or high-speed lifts, the motor can transition from an “electric” state to a “dynamic” state, temporarily becoming a generator. This phenomenon results in regenerative energy flowing back into the system, which can cause voltage spikes and potentially damage the frequency converter’s components. To mitigate these issues, brake units and braking resistors are often integrated into the system. This article delves into the workings of a brake unit, its circuit diagram, and troubleshooting tips.

Structural diagram of braking unit

The Role of Brake Units

When a motor decelerates, brakes, or lowers a heavy load, the mechanical system’s potential energy can cause the motor’s actual speed to exceed the frequency converter’s set speed. This leads to a capacitive current in the motor windings, which generates excitation electromotive force, causing the motor to self-excite and generate electricity. This electrical energy is then fed back into the power grid. However, this regenerative energy can cause the voltage in the frequency converter’s DC circuit to rise sharply, potentially damaging the energy storage capacitors and inverter module.

To prevent this, brake units and braking resistors are used. A brake unit is essentially an electronic switch (IGBT module) that, when activated, connects the braking resistor to the DC circuit. This rapidly dissipates the motor’s regenerative energy as heat, keeping the DC circuit voltage within safe limits.

Circuit Analysis

The brake unit’s control circuit typically includes a DC voltage detection circuit that triggers the electronic switch when the DC circuit voltage exceeds a certain threshold (e.g., 660V). Once the voltage drops below a lower threshold (e.g., 620V), the switch turns off.

In more advanced systems, the brake unit’s performance is optimized through pulse braking. Here, a voltage/frequency or voltage/pulse width conversion circuit controls the IGBT module’s on/off state. When the DC circuit voltage is high, the braking unit operates at a higher frequency or longer conduction cycle, and vice versa.

Electronic circuit diagram of brake unit control part

The CDBR-4030C Brake Unit

The CDBR-4030C brake unit, while not the most optimized in terms of structure and performance, is still effective in practice. It uses a dual-tube IGBT module, although only one tube is utilized, making it somewhat inefficient. The protective circuit combines electronic and mechanical trip circuits, with the QF0 air circuit breaker modified to trip when the module overheats.

Common Faults and Repairs

Faults in the brake unit often occur in the control power supply circuit, such as an open circuit in the step-down resistor or a breakdown in the voltage regulator. Additionally, moisture can reduce the insulation in the frequency converter’s DC circuit, leading to high voltage discharge and circuit board damage.

The brake unit’s control circuit typically includes an LM393 operational amplifier, a CD4081BE four-input AND gate, and a 7555 (NE555) timer circuit. Troubleshooting involves checking these components and their connections.

One unique feature of the circuit is the hysteresis voltage comparator, which prevents frequent output fluctuations by providing a certain hysteresis voltage. If the braking unit fails to operate correctly, it could be due to issues in this comparator or the voltage comparator connection.

Protective Measures

The circuit also includes protective measures to prevent damage to the IGBT module. For instance, if the module temperature rises to 75°C, a temperature relay triggers a trip, cutting off the brake unit’s power supply. Additionally, the circuit design ensures that if the braking resistor remains connected or the IGBT module fails, the system will shut down to prevent further damage.

Conclusion

Understanding the workings of a brake unit and its circuit diagram is essential for effective troubleshooting and repair. By analyzing the control principle and common faults, technicians can quickly diagnose and resolve issues, ensuring the smooth operation of frequency converters in industrial applications. With proper maintenance and repairs, brake units can provide reliable protection against voltage spikes and regenerative energy, prolonging the lifespan of frequency converters and their components.

Posted on by — Leave a comment

Repairing a 22kW HC1 Drive Module Malfunction: A Detailed Guide

When dealing with the repair of a 22kW HC1 drive, it’s crucial to approach the process methodically, especially when encountering complex issues such as a blown fuse in the inverter module power supply series connection. This particular case study illustrates the step-by-step diagnosis and resolution of such a problem, highlighting the importance of thorough inspection and precise troubleshooting.

Initial Diagnosis and Fuse Replacement

The initial indication of trouble was the blown fuse in the inverter module’s power supply series connection. With no other abnormalities detected in the main circuit measurements, it was tempting to assume that simply replacing the fuse would resolve the issue. However, upon reinstalling the fuse and powering the inverter to 24V, the system immediately triggered an EOCn error code, indicating an overcurrent during acceleration or a short circuit on the motor side. This clear sign of ongoing malfunction signaled that the problem was more complex than just a blown fuse.

In-Depth Investigation of the Driver Circuit

With the fuse replacement failing to solve the issue, the next step was to dismantle and recheck the driver circuit board. A meticulous examination revealed that one of the driver circuits was not outputting a positive excitation pulse. Further investigation led to the discovery of a faulty power amplifier tube (lower tube) in the driver circuit. This component had broken down, causing the voltage terminal of the module trigger terminal to be continuously embedded in negative pressure.

The faulty amplifier tube was replaced, and the pulse circuit returned to normal operation. This repair seemed promising, so the machine was reassembled, connected to a 24V power supply, and powered on. However, the system immediately tripped with an EfbS error, indicating that the fuse had blown again.

Further Diagnostic Measures

To pinpoint the exact cause of the repeated fuse blowing, the 24V power supply was removed, and the original fuse terminals were replaced with light bulbs in series. This setup allowed for visual confirmation of power transmission, with the bulbs emitting strong light upon power-up. During a power outage, the trigger terminal was removed, and individual measurements of the module showed no abnormalities.

With the fuse replaced once more and the inverter circuit reconnected to the 24V power supply, the frequency converter was started. As the frequency rose to around 5Hz, the ECOn error would still trip, indicating persistent issues. At this point, it was unclear whether the problem lay in the module or the driver circuit.

Comprehensive Module and Driver Circuit Testing

To further narrow down the problem, the positive and negative voltage and current of the drive output were checked, and both were found to be normal. This finding suggested a possible module malfunction. To confirm this, all three modules were removed and placed on a workbench for power testing alongside the driver board.

Upon powering on the setup, it was observed that the negative pressure on one arm was unusually low, approximately 2V. Disconnecting the trigger terminal restored the negative pressure to its normal value. However, when the module trigger terminal was reinserted, the negative pressure decreased again. This confirmed that the module was indeed damaged.

Final Resolution

With the damaged module identified, it was replaced with a new one. After reinstalling the repaired components, the system was powered on and tested. This time, there were no error codes, and the drive operated smoothly without any issues. The fault had been successfully repaired, and the 22kW HC1 drive was restored to full functionality.

Conclusion

This case study underscores the importance of a systematic and thorough approach to troubleshooting and repairing complex electronic systems like the 22kW HC1 drive. By carefully examining each component and testing various scenarios, the root cause of the malfunction was identified and resolved. It also highlights the value of using diagnostic tools and techniques, such as replacing fuse terminals with light bulbs, to visually confirm power transmission and isolate faulty components. In the end, a combination of meticulous inspection, precise testing, and replacing damaged components led to a successful repair.

Posted on by — Leave a comment

Troubleshooting and Repairing the Shanghai Rihong CHRH-415AEE 1.5kW Variable Speed Drive (VSD)

Repairing electronic equipment, especially complex devices like variable speed drives (VSDs), often requires a meticulous approach to diagnosing and solving issues. A recent repair case involving the Shanghai Rihong CHRH-415AEE 1.5kW VSD highlights the importance of thorough inspection and the unexpected twists that can arise during the troubleshooting process.

The user of the CHRH-415AEE VSD reported experiencing unstable output and motor jumping, indicating a potential issue within the drive’s operation. Initially, the output module and other critical components were examined and found to be functioning normally. This preliminary check ruled out any straightforward hardware failures, prompting a deeper investigation.

To delve into the problem, the inverter module was disconnected from its power supply. This step was crucial to isolate and assess the quality of the inverter pulse conveying circuit, including the driving circuit. The VSD was then reassembled as a complete unit on the maintenance bench, without the machine cover, and powered on for inspection.

Upon powering up, the operation panel displayed normal readings, suggesting that the basic functionality of the control interface was intact. However, when attempting to start the operation, an “E OH” error code appeared, indicating an overheating issue. This was puzzling, as there were no apparent signs of overheating, and the thermal signal output terminals of the short-circuit modules T1 and T2 were not active.

To further investigate, the thermal signal terminal was disconnected, and the original wiring terminal was connected to a potentiometer for voltage regulation. This test, however, yielded no significant changes, and the overheating error persisted. At this point, it was necessary to consult the internal circuit diagram of the module to understand the signal flow and identify any potential anomalies.

The circuit diagram revealed that the terminal in question was equipped with a thermistor (rated at 10k ohms at zero degrees Celsius). This thermistor was connected to an external +5V resistor to divide the voltage, which was then directly sent to the CPU. Based on room temperature, the expected voltage at this point should have been below 2.5V. Measurements confirmed that the voltage was indeed 2.3V, indicating that the built-in thermal element and circuit were functioning correctly.

Despite these findings, the overheating error continued to plague the VSD. It was at this juncture that a fortuitous discovery was made. During the inspection, it was noticed that a small square shielding iron sheet had been wrapped around the back of the operation panel. When the operation panel was pressed, one corner of this iron sheet made contact with the 41st pin of the CPU. This particular pin happened to be the input pin for the overheat signal.

The contact between the iron sheet and the CPU pin was creating a false overheating signal, essentially tricking the CPU into thinking that the module was overheating. This was a highly unusual and coincidental issue, but it explained the persistent “E OH” error code. To resolve this problem, a piece of cardboard was placed between the operation panel and the motherboard circuit. This simple yet effective solution prevented the iron sheet from making contact with the CPU pin, eliminating the false overheating signal.

With the root cause identified, the focus shifted to repairing the faulty driver circuit. It was determined that the driver IC (integrated circuit) was likely responsible for the issue. The driver IC was replaced with a new one, and the VSD was reassembled and tested. After the repair, the VSD performed flawlessly, with no more overheating errors or unstable output issues.

This case underscores the importance of meticulous inspection and the willingness to explore unconventional possibilities when troubleshooting electronic equipment. The repair process not only required technical knowledge but also a dose of creativity and persistence to solve the puzzling issue. In the end, the successful repair of the Shanghai Rihong CHRH-415AEE 1.5kW VSD was a testament to the power of thorough diagnostics and innovative problem-solving.

Posted on by — Leave a comment

Exploring the Major Causes of Damage to Inverter Output Modules

Exploring the Major Causes of Damage to Inverter Output Modules

In variable speed drive (VSD) systems, damage to the inverter output module is an issue that cannot be ignored. This article delves into several primary reasons behind this failure, analyzing the underlying logic and mechanisms to provide valuable insights for relevant practitioners.

I. Damage Caused by Abnormal Loads

Despite the considerable sophistication of protective circuits in inverters, their protective capabilities may still be limited when faced with abnormal loads. Inverter manufacturers have invested significant effort in protecting inverter modules, employing various measures such as output current detection and IGBT voltage drop detection to achieve the fastest possible overload protection. However, when motors themselves have underlying issues like insulation aging or winding defects, even comprehensive protective functions of the inverter may not fully prevent module damage.

Especially in cases where motors have been operating for many years and their insulation has significantly degraded, connecting them to inverters may result in voltage breakdowns between windings due to high-frequency carrier voltages, leading to short-circuit currents that can instantly subject the inverter module to enormous shocks, causing damage. This type of module damage, triggered by internal motor faults, is difficult for inverter protective circuits to effectively prevent.

II. Damage Caused by Inverter Circuit Issues

  1. Drive Circuit Failures
    The drive circuit is a crucial component of the inverter module, typically supplied by both positive and negative power sources. When the +15V voltage is insufficient or lost, the IGBT cannot be turned on. If the drive circuit’s fault detection function is working properly, the inverter will report an OC signal and shut down for protection. However, if the -5V off-voltage is insufficient or lost, it may cause the IGBT to mistakenly turn on, creating a short circuit that can deal a fatal blow to the module.
  2. Poor Pulse Transmission Path
    The PWM inversion pulses output by the CPU pass through a buffer before being sent to the drive IC and then to the trigger terminals of the inverter module. Any interruption in this transmission path can cause the inverter to report an OC fault or operate in an unbalanced phase. Unbalanced phase operation generates DC components and surge currents, which can impact the module and increase the risk of damage.
  3. Failure of Detection Circuits
    Current detection circuits and module temperature detection circuits are important barriers for protecting the inverter module. If these circuits fail or malfunction, they will be unable to effectively monitor overcurrent and overheating conditions in the module, thereby losing their protective function.
  4. Decrease in Energy Storage Capacitor Capacity
    A decrease in the capacity of the energy storage capacitor in the main DC circuit increases the pulsating components of the DC circuit voltage. During loaded startup, this can cause the inverter module to withstand excessive voltage shocks, leading to damage.

III. Damage Caused by Product Quality Issues

In the market, some domestically produced inverters are criticized for their poor quality and shoddy workmanship. These inverters have obvious deficiencies in the design of protective circuits and the selection of inverter module capacities, making the modules prone to damage. For example, using small-capacity modules, old or defective modules, and ineffective protective circuits significantly increase the risk of module damage.

Conclusion

In summary, the damage to inverter output modules is a result of multiple factors working together. To reduce the risk of module damage, we should approach the issue from multiple angles: strengthen motor maintenance and inspection to ensure motors are in good condition; optimize inverter design to improve the reliability and response speed of protective circuits; and, when choosing inverters, consumers should prioritize product quality and after-sales service to avoid purchasing inferior products. Only in this way can we more effectively protect the safe operation of inverter output modules and extend the lifespan of inverters.

Posted on by — Leave a comment

Troubleshooting a Convo Frequency Converter: A Case Study

When dealing with complex electronic devices like frequency converters, troubleshooting can often be a challenging task. This article presents a detailed case study of a 5.5kW Convo frequency converter that was sent for repair due to issues with its operation. Despite having output, the converter was unable to operate with a load, the motor couldn’t rotate, and the operating frequency couldn’t be adjusted.

Initial Examination and Tests

Upon receiving the unit, the main circuit, rectifier, and inverter circuits were thoroughly checked and found to be normal. With no load connected, the three-phase output voltage was also measured and deemed normal. However, when a 1.1kW no-load motor was connected and the frequency converter was started, the frequency couldn’t rise above one or two hertz. The motor would pause and produce a creaking sound, with no overload or OC fault reported.

Investigating the Drive Circuit

Suspecting an issue with the drive circuit, the 550V DC power supply of the inverter module was disconnected, and a 24V DC low-voltage power supply was used to check the drive circuit. All capacitors and components in the drive circuit and drive power supply circuit were normal. The positive and negative pulse currents output by the three-arm drive circuit on the inverter output had reached a sufficient amplitude, indicating that there should be no issue driving the IGBT module.

However, when measuring the pulse currents, a module fault was reported. Upon analysis, it was discovered that the multimeter’s DC current range had been directly short-circuited to measure the triggering terminal, lowering the positive excitation voltage output by the drive circuit. This voltage drop prevented the IGBT tube from being triggered normally and reliably, leading to the OC module fault. When the measurement method was adjusted by connecting the probe in series with a resistance of over ten ohms, the OC fault was no longer reported.

Further Investigation

With the drive circuit functioning normally, the signal output circuit of the current transformer was also checked and found to be normal. During operation, no fault signal was reported, leaving the technician puzzled.

Considering the possibility that the CPU might be detecting abnormal current during startup and taking measures to slow down, the technician explored various potential causes:

  • Abnormal Current Detection: Could the CPU be detecting a sharp increase in abnormal current values and performing immediate frequency reduction processing?
  • Driving Circuit Issues: Was the current limiting action due to abnormal driving or poor module performance?

Attempts to short-circuit the shunt resistors of the U, V, and W output circuits to make the CPU exit the frequency reduction and current limiting action were ineffective. Restoring the parameters to their factory values also had no impact.

Observing the Frequency Converter’s Behavior

Upon starting the frequency converter and observing its behavior, it was noticed that after the speed rose to 3Hz, it would drop to 0Hz and repeat this process. The motor would stop running. When the acceleration time was significantly increased, the speed steadily increased to 3Hz and then decreased to 0Hz, indicating that there were no abnormalities in the drive and other circuits. This operating phenomenon seemed to be based on a signal emitted by the CPU, possibly as a current limiting action based on the current signal.

Focusing on Voltage

With the drive and current detection circuits functioning normally, the technician shifted their focus to voltage. The anomalies caused by voltage could be divided into two aspects:

  1. Abnormal DC Voltage Detection Circuit: This could be due to the drift of the reference voltage, variation of sampling resistance, or other issues. This signal might cause the CPU to mistakenly assume that the voltage is too low and take measures to reduce the output frequency.
  2. Abnormality of the Main DC Circuit: This could result in low voltage due to issues like loss of capacity of the energy storage capacitor or failure to close the charging short-circuit contactor.

Discovery of the Issue

Upon reinstalling and powering on the machine for a motor test, it was noticed that there was no sound of the charging contactor closing. Checking the contactor coil revealed that it was supposed to receive AC 380V from the R and S power supply incoming terminals. However, loose coil lead terminals had caused poor contact, preventing the contactor from engaging. The large current during startup created a significant voltage drop on the charging resistor, which was detected by the voltage detection circuit, prompting the CPU to issue a frequency reduction command.

Conclusion

The reason for the detour in troubleshooting was that the machine only performed frequency reduction treatment when the voltage dropped and did not report an undervoltage fault. In this case, other models might have reported an undervoltage fault. Due to the no-load condition, the voltage quickly rose during frequency reduction processing, allowing the frequency to continue to rise. This repeated process caused the frequency converter to increase speed, decrease to zero speed, pause, and then repeat the cycle without shutting down or reporting any fault signals.

This case study highlights the importance of thorough investigation and detailed observation in troubleshooting complex electronic devices. Relying solely on surface phenomena and past experience can lead to misdiagnosis and unnecessary repairs. By delving deeper into the issue and considering all potential causes, the technician was able to identify and fix the problem, ensuring the frequency converter’s proper operation.

Posted on by — Leave a comment

Solving Two Unusual Faults in AMB VSD: A Detailed Guide

When dealing with variable speed drives (VSDs), encountering unusual faults can be both perplexing and time-consuming. This article will delve into two unique faults encountered in an Anbang Xin AMB-G9/P9 22kW frequency converter and provide step-by-step solutions to resolve them.

Fault A: Mysterious “Fault Characters”

A user sent in a domestically produced frequency converter for repair, specifically an Anbang Xin AMB-G9/P9 22kW model. Upon initial inspection, the damaged module was removed, and the drive circuit was tested for normalcy. Upon powering on, the operation panel displayed an OC fault code. Once the short-circuit fault signal was addressed, the OC signal stabilized. However, when attempting to run the converter by pressing the RUN button, the charging relay momentarily disconnected, causing the panel indicator light to go out and the display screen to flash a series of unrecognizable “fault characters” not listed in the fault code table.

Diagnosis and Solution:
  1. Identify the Anomaly:
    • The output terminals of the three-phase output current detection signal were all at 0V, which is normal.
    • Occasionally, upon cycling the power, it was discovered that the “fault characters” were actually startup characters.
  2. Root Cause Analysis:
    • The malfunction indicated a possible short-circuit load on the switching power supply’s load side, particularly in the driving circuit.
    • When the startup signal was activated, the power supply voltage dropped significantly, causing the switching power supply to stop oscillating.
    • This voltage drop also released the charging relay due to insufficient suction voltage, prompting the CPU to believe it was being re-powered on and displaying startup characters.
  3. Circuit Inspection:
    • Examination of the driving circuit revealed that two power amplification tubes, connected in a push-pull configuration behind the driving IC, had sustained damage.
    • One transistor in both the upper and lower arm driving power amplifier circuits of the U-phase was damaged.
    • This damage caused an instantaneous short circuit to the driving power supply when pulse signals arrived, resulting in a momentary shutdown.
  4. Resolution:
    • Conduct a thorough inspection of the driver board before powering on after dismantling the module.
    • Replace the damaged transistors in the driving circuit to ensure proper pulse amplification and module driving.

Fault B: Unlisted Fault Characters Related to the Brake Circuit

After replacing the module, the converter was tested with a 24V DC power supply without connecting the 530V DC voltage of the DC circuit. Upon startup, the Br Tr FeiLuRe character appeared but could be reset with the reset button. However, disconnecting the 24V power supply resulted in the fault persisting and becoming unresettable.

Diagnosis and Solution:
  1. Initial Checks:
    • The fault code was checked, and the manufacturer indicated it was a brake circuit fault, which seemed unusual given that the external brake resistor circuit was not connected.
    • Internal brake components were measured and found to have no short circuits.
  2. Voltage Analysis:
    • Upon disconnecting the 24V power supply, a residual voltage of about 6V was found at the inverter power supply terminal.
    • This voltage entered the fault detection circuit, potentially triggering the Br Tr FeiLuRe fault signal.
  3. Circuit Examination:
    • The negative pressure and pulse positive voltage of the six drive circuits were normal.
    • With the guarantee of cut-off negative pressure, connecting the 530V DC voltage to the DC circuit should not damage the module.
  4. Testing and Resolution:
    • For safety, the original 75A quick release fuse was replaced with a 2A one.
    • Everything operated normally after this change, indicating that a faulty fuse or short-circuited brake control IGBT inside the module could generate the Br Tr FeiLuRe alarm.
    • The fault detection circuit likely reported an abnormal low voltage in the DC circuit to the CPU as a brake circuit fault.
  5. Final Considerations:
    • Defining the fault as a brake circuit issue may be misleading.
    • The occurrence of this fault prevented low-voltage power supply testing of the inverter circuits, increasing maintenance costs and complexity.

Conclusion

Encountering unusual faults in VSDs requires a systematic approach to diagnosis and resolution. By carefully examining circuit components, analyzing voltage anomalies, and conducting thorough testing, these complex issues can be resolved effectively. This case study highlights the importance of detailed inspection and the potential pitfalls of misdiagnosed faults, ultimately leading to successful repairs and improved understanding of VSD operation.