Cold Test for VFD

With the help of a True RMS multi-meter which has Diode mode available, perform a cold check on the Diode and IGBT on the VFD before powering on. Keep the negative and positive lead of the multimeter as per the tables given below to check the healthiness of Diode and IGBT respectively.

 

Diode Symbol in True RMS Multimeter

Input Diode Test

Step No	Multimeter (+Lead)	Multimeter (- Lead)	Expected Reading
1	R/L1 Terminal S/L2 Terminal T/L3 Terminal	DC Bus Terminal (+)	Approximately 0.5 Volts
2	R/L1 Terminal S/L2 Terminal T/L3 Terminal	DC Bus Terminal (-)	OL Displayed
3	DC Bus Terminal (-)	R/L1 Terminal S/L2 Terminal T/L3 Terminal	Approximately 0.5 Volts
4	DC Bus Terminal (+)	R/L1 Terminal S/L2 Terminal T/L3 Terminal	OL Displayed

 

Input Diode Test -R/L1 terminal to (-) terminal

 Ouptut IGBT Test

Step No	Multimeter (+Lead)	Multimeter (- Lead)	Expected Reading
1	U/T1 Terminal V/T2 Terminal W/T3 Terminal	DC Bus Terminal (+)	Approximately 0.5 Volts
2	U/T1 Terminal V/T2 Terminal W/T3 Terminal	DC Bus Terminal (-)	OL Displayed
3	DC Bus Terminal (-)	U/T1 Terminal V/T2 Terminal W/T3 Terminal	Approximately 0.5 Volts
4	DC Bus Terminal (+)	U/T1 Terminal V/T2 Terminal W/T3 Terminal	OL Displayed

 

Ouptut IGBT Test (+) terminal to W/T3 terminal

 NOTE : The value maybe varied when measuring the different VFD