30-60kVA 3-phase Frequency Converter Troubleshooting

High quality power supplies are essential in the R&D and production lines of electrical and electronic manufacturing companies. GoHz Frequency Converter is a specialized AC power source to simulate worldwide electric power to make your appliances work in its perfect circumstance. By installing GoHz frequency converter, you can run American 60Hz machines (for both single phase and three phase machines) to in European 50Hz electric power grid, vice versa, or even get 400Hz output for aircrafts. This article illustrates the potential problems of running a GoHz three phase frequency converter (30kVA, 45kVA, 60kVA), and how to solve such problems.

Content
Part.1: GoHz Frequency Converter Overview
Part.2: GoHz Frequency Converter Inner Parts

1. Front display circuit boards
2. Bottom side parts
3. Middle side parts
4. Top side parts
5. Mainboards

Part.3: Inner Parts Measurement

1. Fuse measurement
2. CBB65 measurement
3. 9V transformer measurement
4. 17V transformer measurement
5. 22V transformer measurement
6. Contactor measurement
7. IGBT module measurement
8. Driver board measurement

Part.4: General Faults Troubleshooting

1. Display screen off
2. No voltage output (no warning)
3. Frequency, voltage bouncing, along with abnormal noise
4. No voltage output (warning)

Part.1 GoHz Frequency Converter Overview

Part.2 GoHz Frequency Converter Inner Parts

Front display circuit boards


Bottom side parts

Middle side parts

Top side parts

Mainboard
Open the left side cover of GoHz frequency converter, and the front side cover, the mainboards are behind the front side cover.

Part.3 Inner Parts Measurement
Note: The 6800UF electrolytic capacitor should be discharged before measurement, a bulb or a resistor (≥20W 500Ω) is a good device for rapid discharging of the capacitor, if don't have such devices, just disconnect the power supply of the frequency converter for 10-20 minutes, make sure the capacitor measured value is less than 5V before proceeding with following steps.

Fuse Measurement
Tools: multi-meter, discharge resistor, slot type screwdriver, cross screwdriver.
Preparation: cut off input power supply, turn off input switch, open the top side cover.

Measure steps:

1. Shift multi-meter to ?, short connect the two headers of the multi-meter, the value should be 0-1 ?.
2. Put the two headers of the multi-meter to the two sides of the fuse, wait for 5 seconds, measured value should be less than 3?, otherwise, it's failed.

CBB65 Capacitor Measurement
Tools: multi-meter, slot type screwdriver, cross screwdriver.
Preparation: cut off input power supply, open the left side cover (W phase) and right side cover (U phase & V phase).

Measure steps:

1. Pry one side plugs on the capacitor by slot type screwdriver, refer to Fig.1, and Fig.2, do it one by one.
2. Shift the multi-meter to capacitance tab to measure the capacitor, refer to Fig.3, the measured values should be greater than 70uF, otherwise, it's failed.
3. Plug the wires back on the capacitor, refer to Fig.4, then measure the next one from the first step.

9V Transformer Measurement
Tools: multi-meter, slot type screwdriver, cross screwdriver.
Preparation: cut off input power supply, open the top side cover.

Measure Steps:

1. Turn off input power supply, open the left side cover of GoHz frequency converter.
2. Unscrew the front-top door, find out the front display circuit board.
3. Turn on input power supply, turn on input switch.
4. Shift multi-meter to AC, measure the 2 terminals as following picture shows, the measured value should be higher than 9v, otherwise, it's failed.

17V Transformer Measurement

1. Turn off input power supply, open the top side cover of GoHz frequency converter, find the 17v transformer; open the front cover, find the connection wires on mainboard.
2. Turn on input power supply, turn on input switch, and press the green ON button.
3. Shift multi-meter to AC, measure the input of the 17v transformer, the measured should be around 220v, otherwise, it's failed.
4. Measure the CN1 plug on the mainboard, the voltage of 1-2 and 3-4 should be 15-19v, otherwise, it's failed.

22V Transformer Measurement

1. Turn off input power supply, open the top side cover of GoHz frequency converter, find the 22v transformer and the connected plug on driver board.
2. Turn on input power supply, turn on input switch, press the green ON button.
3. Shift multi-meter to AC, measure the input of the 22v transformer, the measured should be around 220v, otherwise, it's failed.
4. Measure the voltages of CN1, CN2, CN3, CN4 plugs, the measured value should be 20-24vac, otherwise, it's failed.

AC Contactor Measurement
Open the right side cover, find the AC contactor as following picture shows, Shift multi-meter to ?, press down the top points of the contactor by multi-meter, The unit of measured value should be ?, otherwise, it's failed.

IGBT Module Measurement
Tools: multi-meter, discharge resistor, slot type screwdriver, cross screwdriver.
Preparation: cut off input power supply, turn off input switch, open the top side cover; Discharge 6800uF capacitors by resistor.

Measure steps:
1. Find the CN7 plug of the IGBT on driver board, and unplug it.

2. Shift multi-meter to ?, measure the values of CH1 between 1-2, 1-3, 2-3, record the measured values. The unit of measured value should be K?, otherwise, it's failed.
3. Measure the same for CH2, CH3, CH4.

IGBT CN7 Outlet Measurement
Shift multi-meter to ?, put the black/red header (multi-meter) to 1-2, 4-5, 7-8, 10-11 pins, and record the measured values. The unit of measured value should be K?, otherwise, it's failed.

Single IGBT Measurement

1. Disassemble the baffle, aluminum bars, connection plugs on the IGBTs, keep the wires on E1, E2.
2. Shift multi-meter to ?, put red header (multi-meter) to G1, black header to E1;
3. Put red header to G1, black header to C1;
4. Put red header to C1, black header to E1;
5. Put red header to G2, black header to E2;
6. Put red header to G2, black header to C2;
7. Put red header to C2, black header to E2;

Measure all IGBTs one by one, and record the measured values.

Driver Board Measurement
1. Open the top side cover, find the driver board, turn on input switch, and turn off output switch, power on GoHz frequency converter.
Shift multi-meter to AC, measure the 4 plugs as following picture shows, the measured value should be around 22v, otherwise, it's failed.

2. Shift multi-meter to DC, measure the values of 1-2, 4-5, 7-8, 10-11 of the plug, the measured value should be around 4v, otherwise, it's failed.

Part.4 General Faults Troubleshooting

Display screen off
Troubleshooting steps:

1. Make sure the input power supply is conformed to GoHz frequency converter's specification.
2. Make sure the input switch is ON.
3. Switchover the input switch from ON to OFF for several times.
4. Open the left side covers to check the contactor, see if there is any loosened wire or not.
5. Measure the 9v transformer has output voltage or not, if yes, means the display circuit board failed; if not, means the 9v transformer failed. (Refer to the 9v transformer measurement)

No voltage output (no warning)
Troubleshooting steps:

1. Make sure the input power supply is conformed to GoHz frequency converter's specification.
2. Check if there is a pull-in sound or not when press the ON button.
3. Open the left side cover, turn off output switch, power on frequency converter and press the green ON button, switchover Low/High grade to see if there is a pull-in sound or not, and has voltage output or not.
4. Power on frequency converter to see LED3, LED6 (on mainboard) is lightened or not, if not, check the 17v transformer; If LED6 lighten, LED3 not, replace mainboard.
5. Turn off input switch, cut off input power supply, check the fuse, IGBT is failed or not.

Frequency, voltage bouncing, along with abnormal noise
Troubleshooting steps:

1. Switch to Low Grade, if the voltage is normal in low grade, check CBB65 capacitor failed or not, and the connection wire was loosened or not.
2. Check the terminals of inverter transformer are short circuit or not.
3. Check all of the plugs on mainboard are loosened or not, if not, replace the mainboard.

No voltage output (warning)
Troubleshooting steps:
Find the LED indicators on the mainboards

1. If LED2, LED7 lighten, troubleshooting steps:
a. Turn off input & output switches, discharge 6800uF capacitor;
b. Open the left side cover, check the auxiliary contactor is loosened or not, Fig.1 means good, Fig.2 means failed.

c. Check CN1, CN5 on driver board are loosened or not;

d. Check the 22v transformer is failed or not;
e. Check the R86 (10k) resistor on mainboard is open circuit or not.

2. If LED4, LED7 lighten, troubleshooting steps:
a. Turn off output switch, pull out the CT plug on mainboard; Power on the frequency converter, if it's not warning, means GoHz frequency converter is overloaded;
b. If it's still warning, open the left side cover, check the Cement Resistor is well connected or not, if yes, anticlockwise rotate the potentiometer (on mainboard) for 2-3 cycles, plug back the CT plug and try again.





3. If LED5, LED7 lighten, troubleshooting steps:
a. Check the TEMP plug on the mainboard is poor connection or not; measure the thermo-switch (near the IGBT module) is open circuit or not; measure the 2 points of the thermo-switch by a multimeter, see if the multimeter has bumming sound or not;
b. If LED5, LED7 are lightened after a few working time, check the cooling fans, and see if the ventilation of GoHz frequency converter is good enough or not.

4. If LED7 lighten, troubleshooting steps:
a. Make sure the input power supply is conformed to GoHz frequency converter's specification;
b. Check the Fuse and IGBT are failed or not.

See the video about how to disassemble the enclosure of GoHz frequency converter.

Download PDF copy of the troubleshooting instruction, click here (2.8mb)

Relarted articles: GoHz Frequency Converter Operation Guide, How to choose a Frequency Converter?, GoHz 2-5kVA Frequency Converter Troubleshooting