Measurement Of Voltages And Currents - Mitsubishi Electric FR-D720S SC EC Instruction Manual

Maintenance and inspection
8.2.3

Measurement of voltages and currents

Since voltages and currents in the primary and secondary side of the inverter include harmonics,
different meters indicate different measured values.
When the inverter-to-motor wiring length is large, especially in the 400V class, large-capacity
models, the meters and CTs may generate heat due to line-to-line leakage current. Therefore,
choose the equipment which has enough allowance for the current rating.
When measuring and indicating the output voltage and output current of the inverter, it is rec-
ommended to utilize the AM-5 terminal output function of the inverter. To do this, assign the re-
quired parameter to the terminal.
When using measuring instruments for the normal frequency range, carry out the measure-
ments as described below.
Single-phase, 230 V
Three-phase, 400 V
Power supply
Instrument types
* At, As, Vt, Vs, W12, W13 are only for the three-phase power input
specification models.
Fig. 8-8: Examples of measuring points and instruments
FR-D700 SC EC
Input
voltage
Input
current
Inverter
P/+ N/–
Measurements on the main circuit
Output
voltage
Output
current
To the motor
Moving-iron type
Electrodynamometer type
Moving-coil type
Rectifier type
I002040E
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