Inverter Output Voltage Measurement Techniques - Omron 3G3MX2 User Manual

Maintenance and Inspection
6-4-5

Inverter Output Voltage Measurement Techniques

!HIGH VOLTAGE
Taking voltage measurements around drives equipment requires the right
equipment and a safe approach. You are working with high voltages and high-
frequency switching waveforms that are not pure sinusoids. Digital voltmeters
will not usually produce reliable readings for these waveforms. And, it is usu-
ally risky to connect high voltage signals to oscilloscopes. The inverter output
semiconductors have some leakage, and no-load measurements produce
misleading results. So, we highly recommend using the following circuits to
measure voltage for performing the equipment inspections.
Voltage measurement with load
L1/R U/T1
Inverter Inverter
L2/S V/T2
L3/T W/T3
220 kΩ
2 W
V Class Diode
Bridge
200 V Class 600 V
0.01 A min.
400 V 100 V
Classs 0.1 A min.
Be careful not to touch wiring or connector terminals when working with the
inverters and taking measurements. Be sure to place the measurement cir-
cuitry components above in an insulated housing before using them.
Voltage measurement without load
L1/R
Inverter
L2/S
L3/T
Additional resistor
+ –
Voltmeter V Class
300 V range 200 V Class 600 V
600 V range 400 C Class 100 V
Section 6-4
U/T1
V/T2
W/T3
5 kΩ
30 W
220 kΩ
2 W
+ –
Diode Voltmeter
Bridge
300 V range
0.01 A min.
600 V range
0.1 A min.
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