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How to adjust the power rating of ABB’s ACS510/ACS550/ACS350/ACS355/ACH550 VFDs

With ABB’s ACS510/ACS550/ACS350/ACS355 VFDs, you can easily adjust the power rating through a straightforward process. Whether you want to upgrade a 1.1KW VFD to 5.5KW or vice versa, this flexibility allows you to set the power rating according to your needs. This feature is particularly useful when you have a limited number of VFD main boards, such as SMIO-01C, and need to adapt them to different power ranges. With this adjustment, you can ensure seamless operation even if a VFD in a different power range fails. These are not mentioned in the ABB AC drives PDF manual

  1. How to access and modify parameters:
    Open the parameter table, navigate to the deepest level of parameters, such as 0102, or any other displayed parameters. For example, if it says 9905, then hold the UP (arrow up), DOWN (arrow down), and RETURN (the button on the upper left next to LOC) buttons simultaneously for 3 seconds. You will notice a flash on the screen, and the top line of the screen should show “PARAMETERS+”.
  2. Expanding parameter groups:
    After that, exit and re-enter the parameter groups. Now, you will notice that the number of parameter groups has expanded from the original 99 to a maximum of 120. Navigate to parameter group 105.
  3. Modifying power capacity:
    To modify the relevant power capacity, follow these steps:
    • Find and modify parameter 10509. Change 105.09 to the desired current value and modify the corresponding power value accordingly (make sure it matches theVFD label. For example, if your inverter model is ACS510-01-017A-4, change it to 0174H; for ACS510-01-031A-4, change it to 0314H).
    • Set 10502 to 1 and confirm.
    • Set 10511 to 4012 and confirm.
    Please note that the order of modifications is crucial. If you make a mistake, you may need to start over.
  4. Verifying parameter changes:
    Finally, re-enter the parameter table and check if parameter 3304 (transmission capacity) has been correctly modified.
    To improve SEO performance, here are the optimized suggestions for the above text:

How to access and modify parameters:
Open the parameter table, navigate to the deepest level of parameters, such as 0102, or any other displayed parameters. For example, if it says 9905, then hold the UP (arrow up), DOWN (arrow down), and RETURN (the button on the upper left next to LOC) buttons simultaneously for 3 seconds. You will notice a flash on the screen, and the top line of the screen should show “PARAMETERS+”.

Expanding parameter groups:
After that, exit and re-enter the parameter groups. Now, you will notice that the number of parameter groups has expanded from the original 99 to a maximum of 120. Navigate to parameter group 105.

Modifying power capacity:
To modify the relevant power capacity, follow these steps:

Find and modify parameter 10509. Change 105.09 to the desired current value and modify the corresponding power value accordingly (make sure it matches the VFD label. For example, if your inverter model is ACS510-01-017A-4, change it to 0174H; for ACS510-01-031A-4, change it to 0314H).
Set 10502 to 1 and confirm.
Set 10511 to 4012 and confirm.
Please note that the order of modifications is crucial. If you make a mistake, you may need to start over.

Verifying parameter changes:
Finally, re-enter the parameter table and check if parameter 3304 (transmission capacity) has been correctly modified.

Just a reminder, the process of changing the power above has only been changed to the power of the ABB drive motherboard(SMIO-01C). The power of the drive board has not been changed, although it shows that it can be expanded. In fact, if the power of the power board has not been changed, the actual output power of the variable frequency drive (VFD) has not changed. At the same time, this method is only applicable to ACS510/ACS550/ACS350/ACS355/ACH550 VFDs and is not suitable for ACS800 series inverters. If you would like to know the power modification method for ACS800 inverters, please contact us directly.

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The circuit principle and modification and exchange method of frequency inverter transformer

The current transformers used in frequency inverter circuits, except for a few early products that used traditional transformers wound with through core inductor coils, are often integrated sealed current transformers made of Hall elements and pre current detection circuits (let’s call them electronic current transformers) in mature circuits. They are divided into standard and non-standard types, and the standard type uses specialized molded products in the market. For example, a 10A/1V current transformer generates a 1V signal voltage output for every 10A current in the circuit. Non standard type, designed and customized by the frequency converter manufacturer, cannot be used interchangeably. When damaged, it is generally necessary to replace the same model product provided by the original manufacturer. Of course, with deeper maintenance efforts, different models of current transformers can also be used for emergency repair or improvement, and later replaced.
Electronic current transformers often use some type of sealant for curing, which can cause damage and cannot be restored once removed. What kind of circuits are inside and whether they can be repaired or replaced, causing a lot of speculation. When I was repairing a Fuji frequency inverter, I replaced it with the main board of the TECO frequency inverter. When it was necessary to adjust the A/V ratio of the electronic current transformer, it had to be adjusted by the internal circuit of the transformer. Only then did I make up my mind and use a knife, a saw, and a lot of effort to dissect and map the internal circuits of the current transformers of these three types of frequency inverters. It was hard won.

An electronic current transformer is actually a circuit for a current/voltage converter. The Taian 7.5kW inverter current transformer circuit has a certain representativeness. The main body of the current transformer is also a circular hollow magnetic ring. The U, V, and W output lines of the frequency inverter pass through the iron core magnetic ring as the primary winding (small power models usually pass through multiple turns), and the magnetic ring generates magnetic field lines that vary in density with the output current of the frequency inverter. This magnetic ring has a gap in which a Hall element with four lead terminals is embedded. Hall elements are packaged in sheet form, and the magnetic field lines of the magnetic ring pass through the packaging end face of the Hall element, which is also known as the magnetic field line collection area (or magnetic induction surface). Hall elements convert changes in magnetic field lines into induced voltage outputs. The circuit consists of Hall elements and a precision dual operational amplifier circuit 4570. A constant current of mA (about 3-5mA) level must be added to the operation of the Hall element, and 4570A should be connected as a constant current source output mode to provide the mA level constant current required for the normal operation of the Hall element (the working current of the Hall element in this circuit is about 5.77 mA), which should be added to pins 4 and 2 of the Hall element; The induced voltage that varies with the output current at pins 1 and 3 of the Hall element is applied to the input terminals 2 and 3 of 4570b. Three pins are embedded in the reference voltage (zero potential point), and the change in input voltage of two pins is amplified and output by one pin (current detection signal). Electronic current transformers often have four terminal components, with two terminals supplying power to internal amplifiers of+15V and -15V, the other two terminals serving as signal output terminals, one terminal grounded, and one terminal serving as signal OUT terminal+ In addition to providing power for the dual operational amplifier IC4570, 15V and -15V are further stabilized by 6V to form a zero potential point introduced into the three pins of 4570. When the frequency converter is in a shutdown state, the ground measurement OUT point should be 0V. During operation, it will output an AC signal voltage below 4V in proportion to the output current.

After the electronic current transformer is damaged, it outputs a higher positive or negative DC voltage during static state (when the frequency inverter is shut down), which is mostly due to damage to the internal operational amplifier. Power on self-test of the frequency inverter, which displays a fault code (sometimes without a code in the manual), the frequency inverter will refuse to start or even parameter operation!
The current transformer circuit of TECO 3.7kW frequency converter uses a programmable operational amplifier chip. I have not yet found the model of this chip, but through modification tests, some characteristics of the circuit have been identified. According to the experiment, 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. When short circuiting the solder gaps of pins 11, 12, and 13 step by step, the amplification factor shows a decreasing trend; When opening the circuit step by step, the amplification factor increases. This can adjust the amplification factor of the chip, making it easier to match frequency converters with different power outputs. I successfully applied the current transformer to a 45kW Fuji frequency Inverter by taking corresponding measures.
The voltage detection and current detection signals of the frequency converter may be applied by the program to control the output three-phase voltage and current – when the detection signal changes, the output three-phase voltage and current also change accordingly. When repairing or modifying the original circuit, be careful not to change the original circuit parameters. It is still recommended to use original accessories to repair the frequency converter while maintaining the original circuit form.

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Brake unit circuit diagram and repair ideas

When the speed of the load motor exceeds the output speed of the frequency inverter due to inertia or some other reason, the motor enters the “dynamic” state from the “electric” state, causing the motor to temporarily become a generator. The reverse generated energy of a load motor, also known as regenerative energy.

Some special machinery, such as mining elevators, winches, high-speed elevators, etc., when the electric motor decelerates, brakes, or lowers a heavy load (ordinary large inertia loads, deceleration and parking process), due to the potential energy and potential energy of the mechanical system, the actual speed of the frequency inverter can exceed the given speed of the frequency inverter. The phase of the induced current in the motor winding is ahead of the induced voltage, resulting in capacitive current, The diodes connected in parallel at both ends of the IGBT in the inverter circuit of the frequency converter and the energy storage capacitors in the DC circuit precisely provide a path for this capacitive current. The electric motor generates excitation electromotive force due to capacitive excitation current, which self excites and generates electricity, returning energy to the power supply. This is the process by which an electric motor converts mechanical potential energy into electrical energy and feeds it back to the power grid.

This regenerative energy is rectified by diodes parallel to the inverter circuit of the frequency inverter and fed into the DC circuit of the frequency converter, causing the voltage of the DC circuit to rise from around 530V to 600-700V or even higher. Especially during the process of decelerating and stopping under high inertia loads, it occurs more frequently. This sharp increase in voltage may cause significant voltage and current surges or even damage to the energy storage capacitor and inverter module of the inverter main circuit. Therefore, the braking unit and braking resistor (also known as the braking unit and braking resistor) are often essential components or preferred auxiliary components of the frequency converter. In low-power frequency converters, the braking unit is often integrated into the power module, and the braking resistor is also installed inside the body. But for high-power frequency converters, braking units and braking resistors are selected according to the load operation situation. The CDBR-4030C braking unit is one of the auxiliary configurations of the frequency inverter.

Regardless of the specific circuit, we can first imagine it from the control principle. The so-called braking unit is an electronic switch (IGBT module) that, when turned on, connects the braking resistor (RB) to the DC circuit of the frequency inverter to quickly consume the reverse power generation energy of the motor (converted into heat and dissipated in the ambient air), in order to maintain the voltage of the DC circuit within the allowable value. There is a DC voltage detection circuit that outputs a brake action signal to control the on and off of electronic switches. In terms of performance, when the DC circuit voltage of the frequency converter rises to a certain value (such as 660V or 680V), the switch is turned on to connect the braking resistor RB to the circuit until the voltage drops below 620V (or 620V), and then the switch is turned off, which is also feasible. Anyway, the braking unit has RB’s current limiting function and there is no risk of burning out. If its performance is further optimized, a voltage/frequency (or voltage/pulse width) conversion circuit will be controlled by a voltage detection circuit to control the on/off of the IGBT module in the braking unit. When the voltage of the DC circuit is high, the working frequency of the braking unit is high or the conduction cycle is long. When the voltage is low, the opposite is true. This type of pulse braking has much better performance than direct on/off braking. In addition, with the overcurrent protection and heat dissipation treatment of the IGBT module, this should be a high-performance braking unit circuit.

The CDBR-4030C braking unit is not very optimized in terms of structure and performance, but the actual application effect is still acceptable. The internal electronic switch is a dual tube IGBT module, and the gate and emitter of the upper tube are not used for short circuiting. Only the lower tube is used, which is somewhat wasteful. A single tube IGBT module can be used. The protective circuit is a combination of electronic circuits and mechanical trip circuits. The manufacturer has modified the internal structure of the QF0 air circuit breaker, changing it from leakage trip to trip when the module overheats. Temperature detection and action control are composed of a temperature relay, Q4, and KA1. When the module temperature rises to 75 º C, KA1 action triggers a trip, QF1 trips, and the power supply of the braking unit is turned off, thereby protecting the IGBT module from being burned out due to overcurrent or overheating to a certain extent.
The power supply of the detection circuit (as shown in the figure below) is obtained by reducing the power resistance, stabilizing the voltage with a voltage regulator, and filtering the capacitor, providing a 15V DC power supply.
The faults of the braking unit mainly occur in the control power supply circuit, manifested as open circuit of the step-down resistor, breakdown of the voltage regulator, etc; In addition, due to the introduction of 530V DC high voltage in the DC circuit of the frequency converter, the insulation of the circuit board decreases due to moisture, resulting in high voltage discharge and burning of copper foil strips in large areas of the circuit, as well as short circuits in the integrated blocks of the control circuit. Due to the fact that all circuit boards are coated with black protective paint, the connection and direction of the copper foil strips cannot be clearly seen, which also brings some inconvenience to maintenance.

The circuit consists of an LM393 integrated operational amplifier, a CD4081BE four input and gate circuit, and a 7555 (NE555) time base circuit. The control principle is briefly described as follows:

The DC circuit voltage of the frequency converter introduced by the P and N terminals is divided by the R1 to R7 resistor network and input to the 2 pins of LM339. The 3 pins of LM339 are connected to the set voltage after further voltage stabilization and RP1 adjustment through 15V control power supply. This voltage value is the set voltage of the braking action point. LED1 also serves as a power indicator light. As LM393 is an open collector output operational amplifier circuit, the output terminals of the two amplifiers are connected with pull-up resistors R13 and R14 to provide high-level output during braking action. The first stage amplification circuit is a hysteresis voltage comparator (sometimes also known as a hysteresis comparator), where D1 and R10 are connected to form a positive feedback circuit, providing a certain hysteresis voltage to make the set point voltage fluctuate with the output, avoiding frequent output fluctuations caused by comparing at one point. The second stage amplifier is a typical voltage comparator connection. In essence, the operational amplifier is used here as a switching circuit, without a linear amplification link, but as a switching output. The two-stage amplification circuit forms a phase inversion process for the signal, so that when the output voltage is higher than the set voltage, the circuit has a high-level output.
When LM393 is static, it is a high level output. This high level is superimposed on pin 3 of LM393 through D1 and R10, which “boosts” the voltage value of the braking action set point. When the input voltage of pin 2 (such as 660V DC circuit voltage between P and N) is higher than the voltage of pin 3, pin 1 changes from high level to low level; After the second stage of phase inversion processing, output a high-level signal to pin 1 of CD4081BE. Meanwhile, due to the low level of pin 1 of LM393, pin 3 also dropped from the raised voltage value to the set value. In this way, when the braking unit acts and connects the braking resistor between P and N, the voltage of P and N starts to fall from 660V and continues to fall until the voltage of pin 2 (580V between P and N) is lower than the set voltage value of pin 3. The circuit flips and the braking signal stops outputting, avoiding the unstable output caused by frequent circuit actions at 660V voltage.

The time base circuit 7555 is connected to a typical multi harmonic oscillator and outputs a pulse frequency voltage with a fixed duty cycle. In the LM393 voltage sampling circuit, the braking action signal is output – pin 1 of CD4081BE is a high level, and the high-level component of the rectangular pulse voltage output by the time base circuit 7555 is combined with the high-level signal of LM393, causing pin 3 of CD4081BE to generate a positive voltage pulse output. This pulse is then processed by the master/slave conversion switch, the second stage, and the gate switch circuit. After power amplification by Q1 and Q2 complementary voltage followers, it drives the electronic switch IGBT module.

When the master/slave control switch is turned to the upper end, this machine acts as the master, implements braking action, and transmits braking commands to other slaves through terminals OUT+and OUT -; When the master/slave control switch is turned to the lower end, this machine acts as a slave and receives braking signals from the main unit through terminals IN+and IN -. The signal is input into pin 6 of CD4081BE through optocoupler U5, and braking action is carried out based on the signal from the main unit.
The part of the circuit marked “What is the intention of this circuit” on the blueprint, let’s start from the circuit itself and try to understand the designer’s original intention. If my analysis is incorrect, I hope readers can correct it. Under normal conditions, when implementing a braking action, it can be seen that the braking signal output by U2 is a rectangular pulse sequence signal (this signal is added to pin 1 of U4), and the signal added to pin 2 of U4 through a step-down resistor at the PB terminal is exactly an inverted rectangular pulse sequence signal. At any moment, one of pins 1 and 2 of U4 is always a high level. For the “high out of low” characteristic of the OR gate, pin 3 of U4 always outputs a low level, Q3 is in the cut-off state, and the circuit implements normal braking action; Assuming that the output module has been continuously connected or has been broken down, the signal from the PB terminal to pin 2 of U4 is a DC low level, which is in phase or phase with the pulse signal from pin 1, resulting in an output of “two low and one high”. By driving Q3 through U8, the output signal of pin 3 of U2 is short circuited to ground, causing pin 8 of U2 to also be at a low level until pins 1 and 2 of U4 are completely locked to ground (low) level, and Q3 continues to enter a fully conductive state, completely blocking the braking signal output by U2. Power must be cut off to lift this blockade. But this protective blockade seems powerless and beyond the reach of the module itself in transient overcurrent conditions or faults in the Q1 and Q2 drive circuits themselves.

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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.

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Repair of 22kW HC1 drive module malfunction

A 22kW HC1 drive, the fuse of the inverter module power supply series connection is broken, and no other abnormalities are found in the main circuit measurement. After installation, first send the inverter power supply to 24V and jump EOCn, which means overcurrent during acceleration and short circuit on the motor side. Obviously, there is still a malfunction in the module or driver part. It seems that it’s not just about replacing insurance.

Dismantle and recheck the driver circuit board. It was found that there was no positive excitation pulse output in one of the driver circuits. The power amplifier tube (lower tube) of the driver circuit was found to have broken down, and the voltage terminal of the module trigger terminal was continuously embedded on the negative pressure. After replacing the amplifier tube, the pulse circuit is normal.
Install the machine, connect to 24V power supply, and power on to trip EfbS, which means the fuse is blown. Remove the 24V power supply and replace the original fuse terminals with light bulbs in series, which will emit strong light upon power transmission. But after removing the trigger terminal during power outage, the individual measurement module was normal; Install the insurance and connect the inverter circuit to a 24V power supply. Start the frequency converter, and when the frequency rises to around 5Hz, the ECOn will still trip. I’m not sure if it’s still a problem with the module or the driver circuit.
Recheck the positive and negative voltage and current of the drive output, both are normal. Possible module malfunction. Simply remove all three modules and place them on the workbench for power testing along with the driver board. After powering on, it was detected that the negative pressure on one arm was low, about 2V. Disconnect the trigger terminal, the negative pressure returns to normal value, insert the module trigger terminal, and the negative pressure decreases again. Confirmed that the module was indeed damaged, replaced with a new module, and the fault was repaired.

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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.

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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.

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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.
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Test run failure of the CHRH-415AEE Rihong VSD

Repairing the Shanghai Rihong CHRH-415AEE 1.5kW machine, the user reported unstable output and motor jumping. The output module and output module are both normal. After cutting off the power supply to the inverter module, in order to check the quality of the inverter pulse conveying circuit (including the driving circuit), they were installed as a complete machine on the maintenance bench (without the machine cover installed) and powered on for inspection. The operation panel displays normally, but when starting the operation, it jumps E OH means overheating. The thermal signal output terminals of the short-circuit modules T1 and T2 are invalid. Disconnect the thermal signal terminal and connect the original wiring terminal to the potentiometer for voltage regulation. The test is also ineffective. Check the internal circuit diagram of the module. The terminal is only equipped with a thermistor (10k at zero degrees Celsius), which is connected to an external+5V resistor to divide the voltage and directly send the signal to the CPU. According to room temperature, this partial pressure point should be below 2.5V. The measured voltage is 2.3V, and the built-in thermal element and circuit should be normal.

Later, it was discovered by chance that a small square shielding iron sheet was wrapped around the back of the operation panel. When pressing the operation panel, one corner of this iron sheet touched the 41 pin of the CPU, which happened to be the input pin for the overheat signal. Therefore, pressing the button on the operation panel inputs a module overheating signal (disturbance generated) to the CPU, which is truly a coincidence.
A piece of cardboard is placed between the operation panel and the motherboard circuit, so that when operating the panel, it no longer jumps OH fault code. The fault was quickly identified as a faulty driver circuit, and the machine was repaired by replacing it with a driver IC.

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Several major causes of damage to the inverter output module of the VSD drive

A. Damage caused by abnormal load
Indeed, the protection circuit of the frequency converter is already quite complete. For the protection of expensive inverter modules, various inverter manufacturers have put a lot of effort into their protection circuits, from output current detection to IGBT voltage drop detection in the drive circuit, and strive to implement the fastest overload protection with the fastest strain rate! From voltage detection to current detection, from module temperature detection to phase loss output detection, there has not been a protection circuit for any particular electrical appliance yet. A frequency converter has been focused and invested in this approach. When salespeople talk about the performance of frequency converters, they must also mention the protection function of the frequency converter. They often unconsciously promise users that with the comprehensive protection function of the frequency converter, your motor will not be easily burned. This salesperson doesn’t know that this promise will bring him great passivity!

Does the motor really not burn when using a frequency converter? My answer is: compared to power supply, using a frequency converter makes it easier for the motor to burn, and the motor is prone to burning, making it easier for the inverter module of the frequency converter to be “reimbursed” together. The sensitive overcurrent protection circuit of the frequency converter is at a loss here and has no effect at all. This is a major external cause of damage to the frequency converter module. Listen to me explain the truth behind it.
A motor can operate at power frequency, although the operating current is slightly higher than the rated current, there is a certain temperature rise during long-term operation. This is a faulty motor that can indeed run before it burns out. But after connecting to the frequency converter, frequent overloads may occur, making it impossible to operate. It doesn’t matter yet.
A motor that can operate in power frequency mode and has been used normally by the user for many years. Please pay attention to the word “many years”. Users may think of saving electricity bills or need to undergo frequency conversion modifications due to process modifications. But after connecting to the frequency converter, there will be frequent OC faults, which is good. The protection has stopped and the module is not damaged. What’s scary is that the frequency converter didn’t immediately trip the OC fault, but was running for no reason – after only three or two days of operation, the module exploded and the motor burned out. The user relied on the salesperson: the quality of the frequency converter you installed is poor, burned my motor, you want to compensate my motor!
Prior to this, the motor seemed to have no problems and was running well. The operating current was measured because the load was relatively light, reaching half of the rated current; Tested three-phase power supply, 380V, balanced and stable. It really seems like the damage to the frequency converter, along with the damage to the motor.
If I were present, I would be fair and impartial: don’t blame the frequency converter, it’s because your motor is already “critically ill” and suddenly malfunctioned, accompanied by damage to the frequency converter!
A motor that has been in operation for many years, due to temperature rise and moisture, the insulation degree of the winding has greatly decreased, and even has obvious insulation defects, which are at the critical point of voltage breakdown. In the case of power supply at power frequency, the input voltage of the motor winding is a three-phase 50Hz sine wave voltage, and the induced voltage generated by the winding is also relatively low. The surge component in the circuit is small, and the decrease in the insulation degree of the motor may only bring about inconspicuous “leakage current”. However, the voltage breakdown phenomenon has not yet occurred between the turns and phases of the winding, and the motor is still “operating normally”. It should be said that as the degree of insulation aging deepens, even under power supply at power frequency, it is believed that in the near future, the motor will eventually burn out due to voltage breakdown between phases or windings caused by insulation aging. But the problem is, it hasn’t burned down yet.

After connecting to the frequency converter, the power supply conditions of the motor become “harsh”: the PWM waveform output by the frequency converter is actually a carrier voltage of several kHz or even more than ten kHz, and various components of harmonic voltage will also be generated in the motor winding power supply circuit. According to the characteristics of the inductor, the faster the change rate of the current flowing through the inductor, the higher the induced voltage of the inductor. The induced voltage of the motor winding has increased compared to the power frequency supply. Insulation defects that cannot be exposed during power supply at power frequency are caused by the inability to withstand the impact of induced voltage under high-frequency carriers, resulting in voltage breakdown between turns or phases of the winding. The sudden short circuit of the motor winding was caused by a phase to turn short circuit in the motor winding. During operation, the module exploded and the motor burned out.
In the initial stage of start-up, due to the low output frequency and voltage of the frequency converter, when there is a fault in the load motor, although it causes a large output current, this current is often within the rated value. The current detection circuit acts in a timely manner, and the frequency converter implements a protective shutdown action, so there is no risk of module damage. But if the three-phase output voltage and frequency reach high amplitudes under full speed (or near full speed) operation, if there is voltage breakdown phenomenon in the motor winding, it will instantly form a huge surge current. Before the current detection circuit acts, the inverter module cannot withstand it and will explode and be damaged.
From this, it can be seen that protective circuits are not omnipotent, and any protective circuit has its own weaknesses. The frequency converter is unable to effectively protect the motor winding from sudden voltage breakdown during full speed operation. Not only the frequency converter protection circuit, but any motor protector cannot effectively protect against such sudden faults. When such sudden faults occur, it can only be declared that the motor has indeed passed away.
This type of fault is a fatal blow to the inverter output module of the frequency converter and cannot be avoided.

其它由供电或负载方面引起的原因，如过、欠压、负载重、甚至堵转引起的过流等故障，在变频器的保护电路正常的前提下，是能有效保护模块安全的，模块的损坏机率将大为减小。在此不多讨论。
B、由变频器本身电路不良造成的模块损坏
1、 由驱动电路不良对模块会造成一级危害
由驱动电路的供电方式可知，一般由正、负两个电源供电。+15V电压提供IGBT管子的激励电压，使其开通。-5V提供IGBT管子的截止电压，使其可靠和快速的截止。当+15V电压不足或丢失时，相应的IGBT管子不能开通，若驱动电路的模块故障检测电路也能检测IGBT管子时，则变频器一投入运行信号，即可由模块故障检测电路报出OC信号，变频器实施保护停机动作，对模块几乎无危害性。
而万一-5V截止负压不足或丢失时（如同三相整流桥一样，我们可先把逆变输出电路看成一个逆变桥，则由IGBT管子组成了三个上桥臂和三个下桥臂，如U相上桥臂和U相下桥臂的IGBT管子。）， 当任一相的上（下）桥臂受激励而开通时，相应的下（上）桥臂IGBT管子则因截止负压的丢失，形成由IGBT管子的集-栅结电容对栅-射结电容的充电，导致管子的误导通，两管共通对直流电源形成了短路！其后果是：模块都炸飞了！
截止负压的丢失，一个是驱动IC损坏所造成；还有可能是驱动IC后级的功率推动级（通常由两级互补式电压跟随功率放大器组成）的下管损坏所造成；触发端子引线连接不良；再就是驱动电路的负供电支路不良或电源滤波电容失效。而一旦出现上述现象之一，必将对模块形成致命的打击！是无可挽回的。
2、脉冲传递通路不良，也将对模块形成威胁
由CPU输出的6路PWM逆变脉冲，常经六反相（同相）缓冲器，再送入驱动IC的输入脚，由CPU到驱动IC，再到逆变模块的触发端子，6路信号中只要有一路中断——
a、变频器有可能报出OC故障。逆变桥的下三桥臂IGBT管子，导通时的管压降是经模块故障检测电路检测处理的，而上三桥臂的IGBT管子，在小部分变频器中，有管压降检测，大部分变频器中，是省去了管压降检测电路的。当丢失激励脉冲的IGBT管子，恰好是有管压降检测电路的，则丢失激励脉冲后，检测电路会报出OC故障，变频器停机保护；
b、变频器有可能出现偏相运行。丢失激励脉冲的该路IGBT管子，正是没有管压降检测电路的管子，只有截止负压存在，能使其可靠截止。该相桥臂只有半波输出，导致变频器偏相运行，其后果是电机绕组中产生了直流成分，也形成较大的浪涌电流，从而造成模块的受冲击而损坏！但损坏机率较第一种原因为低。
若此路脉冲传递通路一直是断的，即使模块故障电路不能起到作用，但互感器等电流检测电路能起到作用，也是能起到保护作用的，但就怕这种传递通路因接触不良等故障原因，时通时断，甚至有随机性开断现象，电流检测电路莫名所以，来不及反应，而使变频器造成“断续偏相”输出，形成较大冲击电流而损坏模块。
而电机在此输出状态下会“跳动着”运行，发出“咯楞咯楞”的声音，发热量与损耗大幅度上升，也很容易损坏。
3、电流检测电路和模块温度检测电路失效或故障，对模块起不到有效地过流和过热保护作用，因而造成了模块的损坏。
4、主直流回路的储能电容容量容量下降或失容后，直流回路电压的脉动成分增加，在变频器启动后，在空载和空载时尚不明显，但在带载起动过程中，回路电压浪起涛涌，逆变模块炸裂损坏，保护电路对此也表现得无所适从。
对已经多年运行的变频器，在模块损坏后，不能忽略对直流回路的储能电容容量的检查。电容的完全失容很少碰到，但一旦碰上，在带载启动过程中，将造成逆变模块的损坏，那也是确定无疑的！
C、质量低劣、偷工减料的少部分国产变频器，模块极易损坏
这是国民劣根性的一种体现，民族之痒啊。不错，近几年变频器市场的竞争日趋激烈，变频器的利润空间也是越来越狭窄，但可以通过技术进步，提高生产力等方式来提高自身产品的竞争力。而采用以旧充新、以次充好、并用减小模块容量偷工减料的方式，来增加自己的市场占有率，实是不明智之举呀，纯属一个目光短浅的短期行为呀。
1、质量低劣、精制滥造，使得变频器故障保护电路的故障率上升，逆变模块因得不到保护电路的有效保护，从而使模块损坏的机率上升。
2、逆变模块的容量选取，一般应达到额定电流的2.5倍以上，才有长期安全运行的保障。如30kW变频器，额定电流为60A，模块应选用150A至200A的。用100A的则偏小。但部分生产厂商，竟敢用100A模块安装！更有甚者，还有用旧模块和次品模块的。此类变频器不但在运行中容易损坏模块，而且在启动过程中，模块常常炸裂！现场安装此类变频器的工作人员都害了怕，远远地用一支木棍来按压操作面板的启动按键。
容量偏小的模块，又要能勉强运行，模块超负荷工作，保护电路形成同虚设（按变频器的标注功率容量来保护而不是按模块的实际容量值来保护），模块不出现频繁炸毁，才真是不正常了。
这类机器，因价格低廉，初上市好像很“火”，但用不了多长时间，厂家也只有倒闭一途了。

The reason for the third type of module damage should not have been a single cause. Hopefully, in the near future, the only reasons for module damage will be the first two.
For domestic frequency converters, sometimes it’s just a piece of mouse manure that spoils a pot of soup. Many frequency converters are also quite good, not inferior to foreign products, and they are of good quality and affordable.