Peripheral Equipment; Molded Case Circuit Breaker (Mccb), Residual-Current-Operated Protective Device (Rcd)/Earth Leakage Circuit Breaker (Elcb) And Magnetic Contactor (Mc) - Fuji Electric FRENIC-HVAC User Manual

4.3

Peripheral Equipment

4.3.1 Molded case circuit breaker (MCCB),
residual-current-operated protective device (RCD)/earth
leakage circuit breaker (ELCB) and magnetic contactor (MC)
[ 1 ] Functional overview
MCCBs and RCDs/ELCBs*
Molded Case Circuit Breakers (MCCBs) are designed to protect the power circuits between the power
supply and inverter's main circuit terminals ([L1/R], [L2/S] and [L3/T]) from overload or short-circuit,
which in turn prevents secondary accidents caused by the broken inverter.
Residual-Current-Operated Protective Devices (RCDs)/Earth Leakage Circuit Breakers (ELCBs)
function in the same way as MCCBs.
Built-in overcurrent/overload protective functions protect the inverter itself from failures related to its
input/output lines.
MCs
An MC can be used at both the power input and output sides of the inverter. At each side, the MC
works as described below. When inserted in the output circuit of the inverter, the MC can also switch
the motor drive power supply between the inverter output and commercial power lines.
At the power supply side
Insert an MC in the power supply side of the inverter in order to:
(1) Forcibly cut off the inverter from the power supply (generally, commercial/factory power lines)
with the protective function built into the inverter, or with the external signal input.
(2) Stop the inverter operation in an emergency when the inverter cannot interpret the stop command
due to internal/external circuit failures.
(3) Cut off the inverter from the power supply when the MCCB inserted in the power supply side
cannot cut it off for maintenance or inspection purpose. For the purpose only, it is recommended
that you use an MC capable of turning the MC ON/OFF manually.
Avoid frequent ON/OFF operation of the magnetic contactor (MC) in the input circuit;
otherwise, the inverter failure may result.
The frequency of the MC's ON/OFF should not be more than once per 30 minutes. To assure
10-year or longer service life of the inverter, it should not be more than once per hour.
If frequent start/stop of the motor is required, use FWD/REV terminal signals or the
and keys on the inverter's keypad.
At the output side
Insert an MC in the power output side of the inverter in order to:
(1) Prevent externally turned-around current from being applied to the inverter power output
terminals ([U], [V], and [W]) unexpectedly. An MC should be used, for example, when a circuit
that switches the motor driving power supply between the inverter output and commercial power
lines is connected to the inverter.
If a magnetic contactor (MC) is inserted in the inverter's output (secondary) circuit for
switching the motor to a commercial power or for any other purposes, it should be switched
on and off when both the inverter and motor are completely stopped. This prevents the
contact point from getting rough due to a switching arc of the MC. The MC should not be
equipped with any main circuit surge killer (Fuji SZ-ZM, etc.).
Applying a commercial power to the inverter's output circuit breaks the inverter. To avoid it,
interlock the MC on the motor's commercial power line with the one in the inverter output
circuit so that they are not switched ON at the same time.
(2) Drive more than one motor selectively by a single inverter.
(3) Selectively cut off the motor whose thermal overload relay or equivalent devices have been
activated.
4-5

4.3 Peripheral Equipment

* With overcurrent protection
,