1 Introduction
Although the reliability of the new generation of inverters is already very high, if the equipment is used or maintained improperly or it may still fail for a long time or the operating conditions are not good, shortening the service life of the equipment is bound to cause losses. Therefore, it is very important to deal with the troubleshooting of the inverter.
2 General inverter fault reason
2.1 Analysis of Causes of Over Current Trip (1) When restarting, it trips at a rising speed. This is a very serious over-current performance. The main reasons are:
1) load side short circuit;
2) Work machine jamming;
3) Damage to the inverter tube;
4) The starting torque of the motor is too small and the drive system will not turn back.
(2) When restarting, it does not trip immediately, but it trips during operation. Possible causes:
1) The speed increase time is set too short;
2) The deceleration time is set too short;
3) Larger torque compensation setting causes excessive no-load current at low frequencies;
4) The electronic thermal relay is not properly set and the operating current is set too low, causing malfunction.
2.2 Causes of over-voltage and under-voltage tripping (1) Voltage tripping, mainly due to:
1) The power source voltage is too high;
2) The deceleration time is set too short;
3) During the deceleration process, the regenerative braking discharge unit does not work satisfactorily.
(2) Undervoltage trip, possible causes:
1) The power supply voltage is too low;
2) Phase loss in the power supply;
3) Bridge failure;
2.3 Analysis of reasons why the motor does not turn (1) The function is incorrectly prepared, for example:
1) The upper limit frequency is inconsistent with the highest frequency or the basic frequency and the highest frequency setting. The preset value of the highest frequency must be greater than the preset value of the upper limit frequency and the basic frequency;
2) Using the external timing, the "keyboard given/external given" selection is not preset;
3) Other unreasonable presets;
4) When using the external reference mode, there is no "start" signal: When using an external reference signal, it must be controlled by the start button or other contacts. If you do not need to control by the start button or other contacts, short circuit between RUN (or FWD) and COM terminal.
(2) Other possible causes are:
1) Mechanical jamming phenomenon;
2) The starting torque of the machine is not enough;
3) The frequency converter has a circuit failure.
3 Frequency Converter Troubleshooting and Maintenance Methods
3.1 Inverter has fault diagnosis display data
When the inverter fails, if the inverter has fault diagnosis display data, the processing method is to find out the contents of the indication of the fault in the instruction manual of the inverter, and find out the fault location. The user will check and eliminate the fault according to the instruction manual of the inverter. Faulty component.
3.2 Inverter Fault Diagnosis Display Data
When the frequency converter fails and no fault is displayed, power can no longer be rushed to avoid further damage. At this time, after the power is cut off, do the resistance characteristic parameter test, do the initial search problem.
(1) Inspection of the main circuit:
Take the SANKEN VVVF inverter as an example, open the inverter cover and remove the external leads of all terminals. Check the conduction conditions and resistance characteristic parameters between all terminals such as N, P, Rl, TI, R, 5, T, U, V, and W. The connection between these terminals and the main circuit is shown in Figure 1. Put the pointer multimeter in a 1Ω or 10Ω file, and the test results are shown in Table 1.
Figure 1 The connection between the terminals and the main circuit
The following table shows that the resistance is several Euros to several tens of Euros; if it is not conductive, the resistance is very large and it is more than ten and a thousand Euros.
When measuring the same component, if the test results are found to be inconsistent or very different, it indicates that something is wrong with the component.
For example, when measuring QvP, the black and red pens between P and V are always turned on regardless of measurement, indicating that the GTR is bad and should be further investigated.
The following conditions should be noted: Inspection found that Drp, Dsp, Dtp RP, SP, TP red and black table pen exchange measurement are not pass, can be judged to be rectifier bridge damage, it may be charging resistor RI burned; in Qup, Qvp Qw. In the detection, if Pu, Pv, Pw are not turned on with black and red pens, the judgement may be GTR damage or FusE blow; in the detection of QUN, QVN, QwN, the above situation occurs, except for GTR. In addition, the resistor R may also be damaged.
After the above inspection, to make further judgments, the control board shall be removed, and the resistance of the main circuit R shall be measured in the order of several tens of Euros to zero. If it is turned on, it indicates R1 short-circuit damage or relay adhesion. The components that were initially damaged should be removed for inspection separately and replaced if damaged. Frequency converter CTR above 75kVA is generally used in parallel and should be checked one by one.
(2) Drive circuit check:
After the main circuit is overhauled, connect the control board, pull out the socket of the base of the GTR, connect the external connection, and check whether the digital display is normal and whether the CHARGE lamp is on. In countless displays, check to see if 380V is applied between Rl and Tl. If there is a voltage between R, and Tl check 3052 voltage regulator block has SV voltage, no voltage may be transformer damage, it may be damaged regulator block.
When the CHARGE lamp is off, the main circuit may be without electricity. Check if the voltage between NPs is 540V. If 54OV, then there may be a damaged CHRGE lamp or a problem with the CHRGE lamp circuit.
After the digital display is normal, U/f is set to 0, the frequency is increased to 50 Hz, and the waveforms of Bu1, Bv1, Bw1 and Bu2, Bv2, and Bw2 are measured. The oscilloscope probe test is shown in Table 2. The standard waveform is shown in Figure 2. The voltage is the reference value. Different voltage amplitudes of the inverter are also different. Oscilloscope probe test points are shown in Table 2:
If the waveform is abnormal, it indicates that there is a problem with the detected drive circuit, and the voltages of the drive tube, the components in the drive circuit, and the power supply part should be carefully examined.
Figure 2 GTR drive waveform
(3) Simple measurement of high power transistor (GTR):
If you suspect that there is a problem with the high-power transistor GTR, you can easily seal it off with a multimeter without the GTR test equipment. Check steps are as follows:
1) Turn off the input power and make sure that the CHARGE lamp does not light, and remove the R, 5, T, V, U, and W wiring on the terminals.
2) Remove the connector on the control circuit board and remove the circuit board from the device together with the accessory board.
3) If the module is used in parallel, pull out the parallel terminals in modules BZ, E: and BZx, EZx and test each module as shown in Figures 3, 4, and 5.
Figure 3 Schematic diagram of the GTR module
Note: When the resistance is not on, the resistance is infinity. When the resistance is on, it is several Euros to several tens of Euros. This method can be used to determine whether the selected GTR is available.
Figure 6
(4) Replace the high-power transistor (GTR). If you find a damaged GTR, replace the broken GTR module as follows.
1) Remove the main circuit wiring on the damaged module;
2) Pull out the base control signal wire on the damaged module (when unplugging, hold the terminal plug and do not pull the wire);
3) Unscrew the fixed module screws and take out the damaged module;
4) First select the device that has the same GTR parameter as the one being replaced, and then pass the measurement. Apply a small amount of conductive silicone to the bottom of the GTR. Apply evenly and cover the bottom.
5) Clean the bottom plate of the inverter, place the GTR coated with silicone on the replacement position, tighten the fixing screws, and use a uniform force when tightening the 4 screws;
6) Insert the base signal hidden pin on the base of the GTR. When replacing the device, do not touch the place marked “cannot touch the part by handâ€. The hand should touch the metal after connecting with the ground first. , and then deal with those devices;
7) Restore the control circuit and main circuit wiring;
8) After the connection is completed, use the resistance between the P-N terminal of the multimeter and each output line to determine that no short circuit occurs.