Category: Other Drives

I. High-Voltage Inverter Principles

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:

1. 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.
2. 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.
3. 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.
4. 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

1. 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.
2. 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.
3. 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

1. 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.
2. 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.
3. 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

1. 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.
2. 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.
3. 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.

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.

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.

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.