Q&A - Mitsubishi Electric Melsec Q Series User Manual

9 Troubleshooting
9.3 Q&A
9.3.1 General
To what degree is the module durable against overvoltage and over current? Is external
Q
protective circuit required?
Momentary* : Up to 2 times as high as rated voltage and 20 times as high as rated current.
Continuous : Up to 1.1 times as high as rated voltage and rated current.
A * Momentary means: Energizing 9 times for 0.5 seconds at 1-minute intervals, and then 1 time
for 5 seconds.
External protective circuit is not required.
Q Can the module be used as an electric energy meter?
This module can be used to measure the electric energy and to manage the use of electric
energy.
A
However, it cannot be used for deal and proof of electric energy measurement stipulated in the
measurement law.
Q Are errors in wiring verifiable easily?
They are verifiable by the illuminating condition of "MEA.," "R," "1," and "3" LEDs on the front of
A the module.
Refer to Section 9.2.3 for details.
Q Is it OK to open the secondary terminals of the current sensor?
The secondary side of the models EMU2-CT5, EMU-CT50, EMU-CT100, EMU-CT250,
EMU-CT5-A, EMU-CT50-A, EMU-CT100-A, EMU-CT250-A, EMU-CT400-A, and EMU-CT600-A
is equipped with the protective circuit against opening of secondary terminals. Opening them
during the wiring work causes no problems. However, for safety, please do not continuously
energize the module with the terminals open.
A
The secondary side of the models EMU-CT400 and EMU-CT600 is equipped with the protective
circuit against opening of secondary terminals. However, during the wiring work, be sure to turn
the secondary side short-circuit switch to short. After completion of work, be sure to turn the
secondary short-circuit switch to open. Note that failing to turn the switch open results in an
inaccurate measurement.
Q Is measurement of inverter circuit possible?
Measuring the secondary side of the inverter is impossible due to the large fluctuation of
frequency.
A Make measurement on the primary side of the inverter. However, since a current waveform on
the primary side of the inverter has a distortion containing the harmonic components, a slight
error occurs.
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