10-20kVA 3-phase Frequency Converter Troubleshooting

50Hz and 60Hz power supplies are common used in daily life and industrial machines, most of countries are using either 50Hz or 60Hz, and lots of industrial machines/home appliances are running on either 50Hz or 60Hz, not compatible with both frequency, hence, a device that can change between 50Hz and 60Hz is necessary in global business. then GoHz frequency converter comes, it's a specialized device to convert between 50Hz and 60Hz to make the appliance work at its rated frequency among different countries. But sometimes, an issue may be happened during the long-time operation of the frequency converter, this article illustrates the potential problems of running a GoHz three-phase frequency converter (10kVA, 15kVA, 20kVA), and the methods to solve such problems.

Content

Part.1: GoHz Frequency Converter Overview

Part.2: GoHz Frequency Converter Inner Parts

1. Front display circuit boards
2. Left side bottom parts
3. Left side middle parts
4. Top side parts
5. Right side parts

Part.3: Inner Parts Measurement

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

Part.4: General Faults Troubleshooting

1. Display screen off
2. No voltage output (not warning)
3. Frequency, voltage bouncing, along with abnormal noise
4. No voltage output (warning)

Part.1 GoHz Frequency Converter Overview

①Front ②Left Side	③Top ④Right Side

Part.2 GoHz Frequency Converter Inner Parts

Front display circuit boards

Left side bottom parts

Left side middle parts

Current Transformer

50W Winding Resistor	AC Contactor
CBB65 Capacitor	CBB61 Capacitor

Top side parts

Fuse	6800uF Electrolytic Capacitor
Baffle	Thermo-switch
IGBT Module

Right side parts

Part.3 Inner Parts Measurement

Note: The 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 left & top side covers.

Measure steps:

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

CBB65 Capacitor Measurement
Tools: multi-meter, slot type screwdriver, cross screwdriver.
Preparation: cut off input power supply, turn off input switch, open the left side cover.

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 20uF, otherwise, it's failed.
3. Plug the wires back on the capacitor, 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, turn off input switch, open the right side cover.

Measure Steps:

1. Turn off input power supply, open the left side cover of the 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 right side cover of the frequency converter, find the 17v transformer and the connected plug 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 right side cover of the 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.

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 right & top side covers; 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 Ω, measure the values of CH1 between 1-2, 1-3, 2-3, record the measured values. The unit of measured value should be KΩ, otherwise, it's failed.
3. Measure the same for CH2, CH3, CH4.
   
   
   
   

IGBT CN7 Outlet Measurement
Shift multi-meter to Ω, 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 KΩ, otherwise, it's failed.

IGBT Measurement


1. Disassemble the baffle, aluminum bars, connection plugs on the IGBTs, keep the wires on E1, E2.
2. Shift multi-meter to Ω, 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. Turn on input switch, turn off output switch, power on the 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 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 front & side covers of the frequency converter to check 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 (not warning)
Troubleshooting steps:

1. Make sure the input power supply is conformed to frequency converter's specification.
2. Check if there is a pull-in sound or not when press the ON button.
3. 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. Open the right side cover of the frequency converter, 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)
Open the right side cover of the frequency converter, power on frequency converter.
1. If LED2, LED7 lighten, troubleshooting steps:

1. Turn off input & output switches, discharge 6800uF capacitor;
2. Check the AC contactor auxiliary contacts;
3. Check CN1, CN5 on driver board are loosened or not;
4. Check the 22v transformer is failed or not;
5. Check the R86 (10k) resistor on mainboard is open circuit or not.

2. If LED4, LED7 lighten, troubleshooting steps:

1. Turn off output switch, pull out the CT plug on mainboard; Power on the frequency converter, if it's not warning, means the frequency converter is overloaded;
2. If it's still warning, 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:

1. Check the TEMP plug on the mainboard is poor connection or not; measure the thermo-switch 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;
2. If LED5, LED7 are lightened after a few working time, check the cooling fans, and see if the ventilation of the frequency converter is good enough or not.

4. If LED7 lighten, troubleshooting steps:

1. Make sure the input power supply is conformed to frequency converter's specification;
2. Check the Fuse and IGBT are failed or not.

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