Power-Off And Magnetic Contactor (Mc) - Mitsubishi Electric 800 Series Instruction Manual

Power-OFF and magnetic contactor (MC)

3.4
Power-OFF and magnetic contactor (MC)
Inverter input side magnetic contactor (MC)
On the inverter input side, it is recommended to provide an MC for the following purposes:
(Refer to page 20 for selection.)
• To disconnect the inverter from the power supply at activation of a protective function or at malfunctioning of the driving
system (emergency stop, etc.). For example, an MC prevents overheat or burnout of the brake resistor when heat capacity
of the resistor is insufficient or brake regenerative transistor is damaged with short while connecting a brake resistor.
• To prevent any accident due to an automatic restart at power restoration after an inverter stop made by a power failure.
• To separate the inverter from the power supply to ensure safe maintenance and inspection work.
Use the inverter input current as a reference for selection of an MC to perform an emergency stop during operation, and
select the MC conforming to JEM 1038-AC-3 class rated operational current.
NOTE
• Since repeated inrush currents at power ON will shorten the life of the converter circuit (switching life is about 1,000,000
times), frequent starts and stops of the magnetic contactor must be avoided. Turn ON/OFF the inverter start controlling
terminals (STF, STR) to run/stop the inverter.
Power
supply
Operation preparation
OFF ON
MC
Start/Stop
MC
Start
Stop
RA
Handling of the magnetic contactor on the inverter's output side
Switch the magnetic contactor between the inverter and motor only when both the inverter and motor are at a stop. When the
magnetic contactor is turned ON while the inverter is operating, overcurrent protection of the inverter and such will activate.
When an MC is provided to switch to a commercial power supply, for example, it is recommended to use the electronic bypass
function Pr.135 to Pr.139 (Refer to
dedicated motors nor with PM motors.)
Handling of the manual contactor on the inverter's output side
A PM motor is a synchronous motor with high-performance magnets embedded inside. High-voltage is generated at the motor
terminals while the motor is running even after the inverter power is turned OFF. In an application where the PM motor is
driven by the load even after the inverter is powered OFF, a low-voltage manual contactor must be connected at the inverter's
output side.
NOTE
• Before wiring or inspection for a PM motor, confirm that the PM motor is stopped. In an application, such as fan and blower,
where the motor is driven by the load, a low-voltage manual contactor must be connected at the inverter's output side, and
wiring and inspection must be performed while the contactor is open. Otherwise you may get an electric shock.
• Do not open or close the contactor while the inverter is running (outputting).
72
PRECAUTIONS FOR USE OF THE INVERTER
MCCB
MC
R/L1
S/L2
T/L3
R1/L11
S1/L21
T ∗1
Inverter
MC
RA
STF/STR
SD
RA
page 448). (The commercial power supply operation is not available with vector control
• Inverter start/stop circuit example
As shown on the left, always use the start signal
U
To the
(ON or OFF of STF(STR) signal) to make a start
motor
V
or stop.
W

∗2

C1
B1
A1
Install a stepdown transformer.
Connect the power supply terminals R1/L11,
S1/L21 of the control circuit to the input side
of the MC to hold an alarm signal when the
inverter's protective circuit is activated. At
this time, remove jumpers across terminals
R/L1 and R1/L11 and S/L2 and S1/L21.
(Refer to page 52 for removal of the jumper.)