Shihlin SA3 Series, Руководство пользователя

Страница: 317 / 423

Ways to measure voltage, current , power on main circuit
INSPECTION AND MAINTENANCE 315
6.2.3 Measurement of currents

Use moving-iron type meters on both the input and output sides of inverter. However, if the carrier frequency
exceeds 5kHz, do not use this type of meter since an over-current losses produced in the internal metal parts of
the meter will increase and may burn. In this case, use an approximate-effective value type.

Since current on the inverter input side tends to be unbalanced, measure three phases together is recommended.
Correct value cannot be obtained by measuring only one or two phases. On the other hand, the unbalanced ratio
of each phase of the output side current should be within 10%.

When a clamp ammeter is used, always use an effective value detection type. A mean value detection type
produces a large error and may indicate an extremely smaller value than the actual value. The value monitored
on keypad is accurate if the output frequency varies, and it is recommended to monitor values (provide analog
output) using the keypad.
6.2.4 Measurement of power

Use digital power meters at the input and output terminals of inverter simultaneously, or use electrodynamics
meters at the input and output terminals of inverter simultaneously. Then, measure the power by the 2-power
measurement method or the 3-power measurement method. However, the input terminal current
tends to be
unbalanced, so it is recommended to use 3-power measurement method for measurement.
6.2.5 Measurement of frequency

Default setting of HDO terminal is FM function, a pulse train proportional to the output frequency is output across
terminal HDO and SD.This pulse train output can be counted by a frequency counter, or a meter (moving-coil type
voltmeter) can be used to read the average value of the pulse train output voltage.

Please refer to Section 5.3.9.