3.10 Drive Wiring Protection
102 SIEPYEUOQ2A01A AC Drive Q2A Technical Manual
3.10 Drive Wiring Protection
◆ Install a Molded-Case Circuit Breaker (MCCB) or Residual Current Monitor/
Device (RCM/RCD)
Install a molded-case circuit breaker (MCCB) or a ground fault circuit interrupter (RCM/RCD) for line protection
between the power supply and main circuit power supply input terminals R/L1, S/L2, and T/L3. The MCCB/
RCM/RCD give overload protection and also prevent damage to the main circuit and the devices that are wired to
the main circuit.
Use the information in this section to select the correct MCCB or RCM/RCD and to safely connect the device.
• The capacity of the MCCB or RCM/RCD must be 1.5 to 2 times the rated output current of the drive. Use an
MCCB or RCM/RCD as an alternative to overheat protection (150% for one minute at the rated output current)
to prevent drive faults.
• When you connect more than one drive to one MCCB or RCM/RCD that is shared with other equipment, refer
to Figure 3.56 and use a magnetic contactor (MC) and set a sequence that de-energizes the drive when it outputs
errors.
A - Power Supply B - Drive
Figure 3.56 Connect an MCCB
WARNING! Electrical Shock Hazard. Use an MCCB, RCM/RCD, or Magnetic Contactor (MC) to de-energize the drive before
you wire the main circuit terminal. Failure to obey can cause death or serious injury.
◆ Install a Residual Current Monitoring/Detection (RCM/RCD)
When the drive output does switches at high speeds, it causes high frequency leakage current. To prevent
electrical shock and fires caused by ground fault protection that is not sufficient, install an RCM/RCD.
Use a high frequency RCM/RCD at the power input side of the drive and make sure that each drive has a
minimum cumulative sensitivity amperage of 30 mA. The specialized breaker removes high-frequency leakage
current, and only detects the leakage current from frequency bands that are dangerous to humans.
If a device does not have protection against high frequencies, high frequency leakage currents can cause the
device to malfunction. If you have a malfunction on a device that is not protected, decrease the carrier frequency
of the drive, switch to a better breaker, or use an RCM/RCD with a minimum cumulative sensitivity amperage of
200 mA for each drive.
These conditions can have an effect on leakage current:
• Drive capacity
• Carrier frequency
• Wiring distance and types of motor cables
• EMI/RFI filter
To prevent damage and injury to personnel and drives, use a high-frequency RCM/RCD that is rated for AC and
DC power supplies.
Note:
The manufacturer recommends these RCM/RCDs, which are designed to operate with high frequencies.
• Mitsubishi Electric Corporation; NV series
• Schneider Electric; NS series
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