L100 Inverter
Troubleshooting
and Maintenance
6–11

General Inverter Electrical Measurements

The following table specifies how to measure key system electrical parameters. The

diagrams on the next page show inverter-motor systems and the location of measurement

points for these parameters.

Note 1: Use a meter indicating a fundamental wave effective value for voltage, and meters indicating
total effective values for current and power.
Note 2: The inverter output has a distorted waveform, and low frequencies may cause erroneous
readings. However, the measuring instruments and methods listed above provide comparably
accurate results.
Note 3: A general-purpose digital volt meter (DVM) is not usually suitable to measure a distorted
waveform (not pure sinusoid).
Parameter Circuit location
of measurement Measuring
instrument Notes Reference Value
Supply voltage
E1
ER – across L1 and L2
ES – across L2 and L3
ET – across L3 and L1
Moving-coil
type voltmeter or
rectifier type
voltmeter
Fundamental
wave effective
value
Commercial
supply voltage
(200V class) 200-
240V, 50/60 Hz
400V class 380-
460V, 50/60 Hz
Supply current
I1
Ir – L1, Is – L2, It – L3 Total effective
value —
Supply power
W1
W11 – across L1 and L2
W12 – across L2 and L3 Total effective
value —
Supply power
factor Pf1
—
Output voltage
E0
EU – across U and V
EV – across V and W
EW – across W and U
Rectifier type
voltmeter Total effective
value —
Output current
Io
IU – U
IV – V
IW – W
Moving-coil
ammeter Total effective
value —
Output power
Wo
W01 – across U and V
W02 – across V and W Electronic type
wattmeter Total effective
value —
Output power
factor Pfo
Calculate the output power factor from the output voltage E,
output current I, and output power W. —
Pf1
W1

3E

1

×I1

×

------------------------------100%×=

Pf0
W0

3E

0

×I0

×

------------------------------100%×=

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