Category: Industrial control technology

Debugging, application, and maintenance techniques for industrial control products，Such as Variable speed driver(VSD),Variable frequency driver(VFD),Industrial touch screen,Programmable Logic Controller(PLC),Servo Driver,servo motor,servo amplifier,Servo Controller,etc.

Posted on by — Leave a comment

Adjusting the Power Rating of ABB VFDs: A Step-by-Step Guide

Adjusting the Power Rating of ABB VFDs: A Step-by-Step Guide

When it comes to flexibility in power rating adjustments, ABB’s ACS510/ACS550/ACS350/ACS355/ACH550 Variable Frequency Drives (VFDs) offer a seamless solution. Whether you need to upgrade from a 1.1KW to a 5.5KW VFD or make any other power adjustment, these drives provide the capability to adapt to your specific requirements. This is especially beneficial in scenarios where you have a limited number of VFD main boards, like the SMIO-01C, and need to utilize them across different power ranges. Below is a detailed guide on how to access and modify the power rating parameters of these VFDs.

Accessing and Modifying Parameters

  1. Open the Parameter Table:
    • Navigate to the deepest level of parameters, which may include numbers like 0102 or any other displayed values.
    • If you see 9905, for instance, hold the UP (arrow up), DOWN (arrow down), and RETURN (button next to LOC on the upper left) buttons simultaneously for 3 seconds.
    • You will observe a flash on the screen, and the top line should display “PARAMETERS+”.
  2. Expand Parameter Groups:
    • Exit and re-enter the parameter groups.
    • Notice that the number of parameter groups has increased from 99 to a maximum of 120.
    • Navigate to parameter group 105.

Modifying Power Capacity

Follow these precise steps to adjust the power capacity:

  1. Find and Modify Parameter 10509:
    • Change 105.09 to the desired current value.
    • Ensure the corresponding power value matches the VFD label. For example:
      • For ACS510-01-017A-4, change to 0174H.
      • For ACS510-01-031A-4, change to 0314H.
  2. Set 10502 to 1 and confirm.
  3. Set 10511 to 4012 and confirm.

Note: The order of these modifications is crucial. Any mistake may require you to restart the process.

Verifying Parameter Changes

  • Re-enter the parameter table.
  • Check if parameter 3304 (transmission capacity) reflects the correct modifications.

Important Considerations

  • The process outlined above modifies the power rating on the ABB drive motherboard (SMIO-01C). It does not alter the power of the drive board itself.
  • Despite the appearance of expanded power capabilities, the actual output power of the VFD remains unchanged unless the power board is also modified.
  • This guide is specific to ACS510/ACS550/ACS350/ACS355/ACH550 VFDs and is not applicable to the ACS800 series.

For assistance with power modification methods for ACS800 inverters, please reach out to us directly. Our team is here to help you navigate the intricacies of VFD power adjustments and ensure your equipment operates at its optimal capacity.

Posted on by — Leave a comment

Exploring the Circuitry and Modification Techniques of Frequency Inverter Transformers

In the realm of frequency inverter circuits, transformers have evolved significantly. While early models relied on traditional transformers wound with through-core inductor coils, modern, mature circuits predominantly feature integrated, sealed current transformers constructed using Hall elements and pre-current detection circuits. These are often referred to as electronic current transformers and are categorized as either standard or non-standard types.

Physical picture of frequency converter current sensor

Standard electronic current transformers are readily available molded products in the market. For instance, a 10A/1V current transformer outputs a 1V signal for every 10A of current flowing through the circuit. On the other hand, non-standard types are custom-designed by frequency converter manufacturers and are not interchangeable. In case of damage, replacing them with the same model from the original manufacturer is usually necessary. However, with in-depth maintenance knowledge, different models can sometimes be used as temporary solutions until a permanent replacement is sourced.

The construction of electronic current transformers often involves the use of sealants, making them difficult to repair once damaged. This has led to much curiosity about their internal circuitry and repairability. During my experience repairing a Fuji frequency inverter, I needed to adjust the A/V ratio of the electronic current transformer, which required accessing its internal circuit. This prompted me to carefully dissect and map the internal circuits of current transformers from three different frequency inverter models, a process that was both challenging and rewarding.

At its core, an electronic current transformer is essentially a current-to-voltage converter circuit. The current transformer used in a Taian 7.5kW inverter serves as a representative example. The main body of the transformer is a circular hollow magnetic ring through which the U, V, and W output lines of the frequency inverter pass as the primary winding. As the output current of the frequency inverter varies, the magnetic field lines generated by the magnetic ring also change in density.

Embedded within the gap of this magnetic ring is a Hall element with four lead terminals. The Hall element, packaged in sheet form, has its packaging end face (also known as the magnetic field line collection area or magnetic induction surface) exposed to the magnetic field lines. The Hall element converts changes in magnetic field lines into induced voltage outputs.

Internal circuit diagram of the current sensor in a frequency converter.

The circuit of the current transformer comprises the Hall element and a precision dual operational amplifier circuit, such as the 4570. For the Hall element to operate, a constant current of approximately 3-5mA must be supplied. In this circuit, the 4570A is configured as a constant current source to provide the necessary mA-level constant current for the Hall element (approximately 5.77mA in this case). This current is applied to pins 4 and 2 of the Hall element.

The induced voltage, which varies with the output current, is present at pins 1 and 3 of the Hall element and is applied to the input terminals 2 and 3 of the 4570B. The three pins are connected to a reference voltage (zero potential point), and any change in the input voltage at the two pins is amplified and output by the 4570B.

Electronic current transformers typically have four terminal components: two terminals supply power to the internal amplifiers (+15V and -15V), while the other two serve as signal output terminals (one grounded and one as the signal OUT terminal). In addition to powering the dual operational amplifier IC4570, the +15V and -15V are further stabilized to form a zero potential point that is introduced into the three pins of the 4570. When the frequency converter is off, the ground measurement at the OUT point should read 0V. During operation, it outputs an AC signal voltage proportional to the output current, typically below 4V.

If an electronic current transformer is damaged, it may output a higher positive or negative DC voltage in the static state (when the frequency inverter is off). This is often due to damage to the internal operational amplifier. When the frequency inverter performs a power-on self-test, it may display a fault code (sometimes not listed in the manual) and refuse to start or even operate with its parameters.

The current transformer circuit of a TECO 3.7kW frequency converter utilizes a programmable operational amplifier chip. Although I have not yet identified the specific model of this chip, modification tests have revealed some of its circuit characteristics. Experimental results indicate that pin 2 is the constant current power supply terminal, pins 3 and 4 are the input terminals of the differential amplifier, and pin 13 is the signal output terminal. By short-circuiting the solder gaps of pins 11, 12, and 13 in a stepwise manner, the amplification factor decreases; conversely, opening the circuit step-by-step increases the amplification factor. This adjustability allows for easier matching of the chip with frequency converters of different power outputs. I successfully applied this current transformer to a 45kW Fuji frequency inverter by taking appropriate measures.

It is important to note that the voltage and current detection signals of the frequency converter may be used by the program to control the output three-phase voltage and current. Therefore, when repairing or modifying the original circuit, it is crucial to maintain the original circuit parameters to ensure proper operation. Whenever possible, it is recommended to use original accessories to repair the frequency converter while preserving the original circuit form.

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

Repair process of driving circuit for 22kW Delta frequency Inverter

After checking the drive circuit of the 22kW Delta VFD Drive and replacing it with a new module, the OC will jump upon startup. The module is newly replaced, and all six drive pulses are working properly. I don’t think it should be. Still checking the measurement, the six negative pressures driving the IC during shutdown are all normal, and the six excitation voltages are also normal after startup. It is necessary to first determine whether the fault is caused by the driver IC or the module.

It is necessary to first test the load carrying capacity of the six drive ICs, that is, to measure the trigger current value of their output. Connect a 15 ohm resistor in series to the output terminal, and then connect a 15 ohm resistor in series to the probe to limit the circuit current to around 0.5A. After the start signal is activated, its current output capacity is measured, and it can still provide a dynamic current of about 150mA even when the original trigger circuit is connected normally. The driving circuit of the V-phase lower arm IGBT tube only outputs about 40mA of current, which obviously cannot meet the excitation requirements of the IGBT tube. The root cause of the OC fault lies in this!
There seems to be a misconception about the driving method of IGBT tubes, especially high-power IGBT tubes: IGBT tubes are voltage signal excitation devices, not current type excitation devices. The driving signal only needs to meet the voltage amplitude, without requiring too much current driving capability! I have previously analyzed that even IGBT tubes are essentially current driven devices!
The output signals of the driving ICs (PC929 and PC923) of the machine are amplified by a complementary voltage follower and then supplied to the triggering terminals of the module. The push-pull amplifier was originally a pair of field-effect transistors, but due to the lack of the original type of transistor on hand, it has now been replaced with transistor pairs D1899 and B1261. After modification testing, it should be able to meet the excitation requirements. Check the V-phase lower arm circuit. The resistance from pin 11 (pulse output pin) of PC929 to the subsequent power amplifier circuit was originally 100 ohms, but now it has changed to over 100k, causing D1899 to be unable to fully conduct and the output driving current to be too small. After replacing the resistor, the output current is normal. After replacing the power transistor, the base resistance was not measured, resulting in this phenomenon.
By the way, I measured the negative current supply capacity of the driving circuit when cutting off negative pressure output. The probe is still connected in series with a 15 ohm resistor, and each circuit is around 30mA.
This leads to the conclusion that measuring the output voltage of the driving IC is not as direct and effective as measuring its output current. And it can expose the root cause of the malfunction. When the internal resistance of the circuit output increases due to certain reasons, measuring the driving voltage is often normal, which masks the truth of insufficient driving current.

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

Repair of EDS1000 ENC VFDV Misleading Current Fault

A ENC EDS1000 11kW Inverter will trip to constant speed overcurrent when accelerating to above 40Hz during operation. But in reality, the operating current is much lower than the rated current, and after switching to other frequency converters, the motor runs normally. Check that the six inverter pulse outputs of the driving circuit are all normal. It is determined that the current transformer circuit detection is abnormal. Check the current detection circuit. The output signal of the current transformer is divided by a 3-ohm resistor and a 30 ohm resistor before being supplied to the motherboard. Suspecting that the current transformer is a non-standard product, an external voltage divider network was connected for adjustment. The partial voltage value may not be accurate enough, causing the current sampling value to be too large and mistakenly skipping the current fault. Or there may be drift in the output value of the internal circuit of the current transformer, which can also cause a false skip current fault.

The simplest method is to adjust the external voltage divider network of the current transformer. Reduce the voltage divider resistance value below it to meet the requirements of the subsequent circuit input voltage range. If conditions permit, the panel current display value can be monitored during operation, and the voltage divider resistance value can be adjusted to match the operating current value with the displayed current value. Often in the maintenance department, it is not possible to connect the frequency converter to the rated load for operation. Therefore, first replace the lower resistor with a 100 Ω potentiometer, and then adjust it to the appropriate position during on-site installation and operation.

Posted on by — Leave a comment

Hitachi VFD drive L300P75kW , after repair, installation still jumps “fault”，How to solve ？

A Hitachi L300P75kW Inverter was installed and tested on site after repairing the module fault. When powered on and started, E16.4 or E16.2 jumps. The cause of the fault is a momentary open circuit in the power supply. Stop the machine and measure the three-phase 380V power input. All three phases have 380V and are quite balanced. During operation, when measuring the three-phase output circuit, there is an unstable voltage value in one phase, with fluctuations ranging from 280V to around 350V. The voltage detection circuit of this machine detects the input voltage of T and S phases in the input power supply. When the power grid pollution flash exceeds 15ms, it will protect and shut down. It was determined that the air switch supplying power to the frequency converter had poor contact with one phase, causing the frequency converter to trip E16.4 or E16.2 faults. Upon disassembly and inspection, it was confirmed that a set of contacts had been severely burned out.
Repair after replacing the power switch.

This fault is in a stationary state or a low current state, and due to the virtual connection of the air switch, the abnormal input voltage cannot be detected at all. Only visible when turned on. But due to the abnormal detection of the frequency Inverter, it immediately shuts down for protection. Sometimes, if there is no time to detect, the frequency converter has already stopped. So it’s not easy to detect. It took some effort.

Posted on by — Leave a comment

15kW WEICHI VSD fault repair due to lightning strike

Taking over a 15kW WEICHI frequency inverter, it was damaged by lightning strikes. The motherboard and driver board were both struck by lightning, but fortunately, the module and CPU were not damaged.

Inspection:

  1. Control terminal+10V voltage to 0, no output. This voltage is obtained by stabilizing the+15V of the switching power supply through the LM317 (eight pin SMT IC) circuit. At the moment, there is no LM317 SMT IC at hand, so a 100 Ω resistor and a 10V voltage regulator are used as substitutes for repair;
  2. The LF347 chip IC (four operational amplifier integrated circuit) in the voltage detection circuit is damaged, and the LM324 chip is directly used as a substitute. The functions of each pin are consistent;
  3. The SMT transistor for controlling the charging relay is damaged and replaced with a plastic sealed direct insertion transistor D887.
    All lightning faults have been repaired. The test run is normal.
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.