Ways to measure voltage, current , power on main circuit
INSPECTION AND MAINTENANCE 314
6.2 Ways to measure voltage, current , power on main circuit
6.2.1 Measurement instruments choosing
Since inverter voltage and current on input side and output side includes harmonics, measurement data result may
vary. Choose the instruments below (with commercial power supply) for measurement.
Voltage(V)
Current(A)
Power(kW)
Input side(R/L1, S/L2, T/L3)
Moving-iron type
Moving-iron type
Electrostatic type
DC side(+/P, -/N)
Moving-coil type
---
---
Output side(U/T1, V/T2, W/T3)
Rectifier type
Moving-iron type
Electrostatic type
Note: 1. Please pay attention to the instrument range and polarity;
2. Please pay attention to personal and property safety.
6.2.2 Measurement of voltages
Inverter input side
Input side voltage has a sine wave and with extremely small distortion, accurate measurement can be made with
an ordinary AC meter.
Inverter output side
Since the output side voltage has a PWM-controlled rectangular wave, always use a rectifier type voltmeter.
A pointer type meter cannot be used to measure the output side voltage as it indicates a value much greater than
the actual value.
A moving-iron type meter indicates an effective value which includes harmonics and therefore the value is larger
than that of the fundamental wave.
The value monitored on keypad is the inverter-controlled voltage itself. Hence, that value is accurate and it is
recommended to monitor values (analog output) using keypad.
