Practical inverter without output fault Cheats

- Nov 10, 2017 -

Inverter no output fault, is a common fault, the fault mechanism and the circuit level is also more broad. This text especially refers to the fault that the output voltage can not be obtained at the output terminal of U, V, W of the inverter under the premise of normal operation and display, from the panel digital display (shows the normal output frequency value), status indicator ( After receiving the operation instruction, the RUN indicator light is on.) The inverter has entered the "normal working state". The MCU of the mainboard also makes such judgment and does not report the relevant fault code or make an abnormal instruction. Inverter is a high degree of intelligence of the equipment, how can such a non-output failure can not make a normal reaction? Then again, the failure of the overhaul, involving MCU MCU 6 PWM output pulse, the middle of the buffer circuit , Drive IC circuit, drive power and inverter power module and other links, and the result of maintenance is a number of circuit segments, all "normal performance", the failure is so distracted: the circuit is normal, but no output, not easy to find out Fault link!

Maintenance of such failures and the encounter rate is very high, "Drive Repair Forum," there is a large number of such help post, indicating that such failures are very representative, it is necessary to make a more in-depth analysis, so the eternal Time and again to use the "depth decryption" the eye of the human eye, hoping this introduction will arouse the attention and discussion, and can benefit from it.

Look at the Forum netizens on the failure of several posts on the performance of such failures can have a clear understanding:

1) Ask Purple Daily inverter repair frequency input without output

Two days before the Taiwan Purple Daily inverter (constant pressure water supply), was struck by lightning, rectifiers, switches, transformers, there are several small pieces, have changed. Now power test shows normal, then load (bulb) no display voltage

Please heroes pointing instructions!

2) Fuji G9 inverter frequency display but no voltage output

Fuji G9 inverter starts running, the panel frequency display can also see the voltage display, but the output terminal has no voltage output (frequency output shows more than twenty HZ), and with the DC output to detect the output of more than 500 volts DC Voltage, there is no voltage on the negative, I do not know what is the reason to seek expert notification, and the same replacement motherboard

3) Mitsubishi A540 5.5 kw inverter can run without output failure

Have a Mitsubishi A540 5.5kw inverter, has now been determined that the module is not bad, power display is normal, can run up to 50HZ to see the panel output voltage is slowly rose to 360V at 0V, showing basically Are normal. But the output is a little voltage, and there is no alarm, test drive IC did not receive the pulse. Please encounter a similar teacher to give pointers, this machine began to undervoltage. Power on hold is 7800 bad put on like, but after running up no output, because there is no 1302H02 information so bad to determine exactly where is broken, so please be familiar to the pointing or the teacher can tell I have a simple method to determine whether the motherboard is broken or the bottom is broken, and now I suspect 1302H02 can not have accessories on hand, please also have experienced teachers give pointers Thank you

4) iG5 series inverter has no output?

Hello everybody! Consult a iG5 series inverter work frequency display is no output, the load is the fan. After the inverter is powered off and reset, the inverter works normally and has voltage output. Little brother contact please master please advise!

5) Kangwo frequency normal start running indicator light but no output What is the problem?

Kangwo frequency normal start running indicator light but no output What is the problem?

6) Why do not output power output?

220V input, can boot, can work, but U V W no electricity output.

Below to see a drive pulse transmission circuit diagram.

This is an example of HLPP001543B 15kW inverter drive pulse transmission channel, the 6-pin PWM pulse output by the MCU pin, the U5 (HC365 three-phase in-phase buffer gate) intermediate buffer / driver stage circuit, the driver IC isolation, the final power Amplifier circuit, amplified input IGBT gate, emitter. Circuit principle of work will not repeat them.


This is a complete inverter pulse transmission channel and power supply circuit.

Motherboard MCU 6 PWM pulse output signal, often through the middle of a buffer / drive circuit, and then enter the final drive circuit (with optical isolation), if you need to drive high power (generally refers to more than 100A power module) module, drive The pulse signal output by the IC also goes through the power amplification circuit of the rear stage, after amplification, it directly drives the IGBT. Driver IC output side of the power supply, usually using 4 or 6 think of isolated power supply; and input side of the power supply, often using +5 V or +5 V by steady flow circuit to handle the power supply, - the driver IC for the light Coupled devices, input and output side of each have a separate power supply, and the formation of an independent power supply circuit, which is the circuit principle analysis and troubleshooting, with particular attention.

This case driver circuit using PC923, PC929 classic circuit structure, the PC929 will be the next three-arm IGBT fault detection signal, the three optocouplers, fed back to the MCU motherboard circuit.

A breakdown of the drive circuit troubleshooting, there is a very common and typical symptoms are: inverter related to start and stop operation and control are normal, the panel can also display the working status, RUN indicator can indicate normal operating conditions, the monitor Output frequency can be displayed normally, the performance of the inverter "all normal", do not report OC, SC, the lack of output failure, but there is no 3-phase output voltage, the inverter is obviously in a "strike." Detection of driver IC and drive power are often normal, the detection of MCU output 6 pulses, there are, indicating buffer / drive circuit (U5 in the above figure) is also working properly, and some maintenance personnel scratched the head: the problem Where exactly is it?

1) The reason for no output failure caused by the power supply of the driver IC and the damage of the driver IC is basically eliminated, and the possibility of the driver IC of the 6-driver power supply being damaged at the same time is almost nonexistent.

2) If the U5 chip is broken or the pin 1 and pin 15 of the control terminal are off, the pulse transmission path will be cut off to show no output fault phenomenon. However, by measuring the pulse voltage value of the input and output pins, it can be easily judged Circuit failure.

3) The abnormality of the power supply at the input side of the driver IC is the cause of the fault of the U, V and W voltage at the output terminal. It is the "first perpetrator" that the inverter operation display is normal but no output. The transistor T16 and the Zener diode Z7 form a constant current output circuit. After the + 5V processing, as the power supply of the 6-way driver IC, when the Zener diode Z7 is short-circuited or the T16 is short-circuited, the steady current disappears. However, Still able to get the power and work properly. When the T16, Z7 or R79, R80 open circuit or Weld, the power supply on the input side of the driver IC disappears, all the drive circuits stop working, and the inverter has no output fault.


Driver IC input side power loss, but the measurement driver IC's input (such as PC5 2,3 feet) seems to still have a "signal voltage" input, which is a more confusing, easy to produce a false alarm! Level circuit to the pulse signal is a minimum level of 0V, the maximum voltage of +5 V rectangular pulse signal, the DC average of about 2.5V or so. When the power supply on the input side of the driver IC is normal, the negative pulse voltage of the inverter pulse arrives, providing the forward conducting current of the internal light-emitting diode on the input side of the driver IC, thereby completing the transmission of the pulse signal. When the positive pulse signal arrives, the reverse blocking bias of the internal light-emitting diode on the input side of the driver IC is formed via R15, R16 and R81 and a large voltage drop is formed on R16 (also That is, a voltage drop is formed on the two input pins of the driver IC). At this time, the pulse voltage between the two pins of the driver IC is detected, and the overhaul person mistakenly believes that the pulse signal of the preceding stage circuit has been normally added to the input terminal of the driver IC , While ignoring the T16 power supply circuit checks, resulting in maintenance work into a "dead end"!

If the AC voltage file, then PC5 input signal between the 2 and 3 feet, then start, stop the operation, the change is obvious, as if the pulse signal has been "normal arrival"; switch to DC file measurement, if you look at the PC5 input 2, the voltage polarity between 2 and 3 feet, the reason of the fault is exposed: T16 power supply is normal, the pulse signal voltage polarity is 2 feet positive, 3 feet is negative. T16 power disappears, the measured pulse voltage polarity is 3 feet positive, 2 feet negative, PC5 internal LED in reverse bias, the driver IC can not be transmitted to the pulse signal circuit.

4) The common power supply on the output side of the driver IC disappears, resulting in no output failure.

Some inverter drive circuit, the next three IGBT IGBT drive signal due to a total of ground, so share a drive circuit, as shown in the PC3, PC8, PC11, assuming a common drive power supply, when the power supply disappears due to failure, that is driven PC3, PC8, PC11 at the same time lose power supply, IGBT three-phase bridge inverter power circuit, the upper three-arm IGBT can get the normal trigger signal, while the lower three-arm IGBT is also lost the trigger signal can not form the output current loop, Output voltage can not be measured at U, V, W output.

In the same way, it will cause the operation to be normal, but there is no output fault in the inverter. The fault phenomenon caused by the abnormal power supply on the input side of the driver IC is almost the same.

Here is a question mark hidden ah (let me simply say a broken secret bar), inverter output, the drive circuit can not return to the motherboard MCU OC signal?

1) When the power supply on the output side of the driver IC is lost, the power supply of PC3, PC8, and PC11 is lost at the same time. The internal IGBT fault detection circuit of course also synchronizes the "strike" signal and the three IGBTs in the lower three arms can not normally open. It can not be transmitted to the MCU circuit;

2) PC929 is by the internal IGBT fault detection circuit - essentially detect the IGBT voltage drop when the signal is turned on. Detection action or detection timing is implemented during the receiving of positive excitation pulse signal. When the power supply on the input side of the driver IC disappears, the PC929 internal detection circuit considers that it has been stopped and no pulse signal arrives. Feedback OC signal.

This means that although the U, V and W terminals of the inverter have no voltage output, no alarm signal is generated. The operation display panel of the inverter still shows the reason of "running normally".

In addition, the MCU has indeed output the normal 6-channel pulse signal, there is no other fault signal back to the MCU, the operating display panel, does not display the "normal state", but also for what to display it?

This is almost the only example in which the inverter is faulty in operation and display status with no output.

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