Mitsubishi Electric 800 Series Hardware Instruction Manual page 91

Checkpoint
The converter unit and the inverter
are correctly connected.
When using the electronic bypass
operation, electrical and
mechanical interlocks are
provided between the electronic
bypass contactors MC1 and MC2.
A countermeasure is provided for
power restoration after a power
failure.
For Vector control, the encoder is
properly installed.
A magnetic contactor (MC) is
installed on the converter unit's
input side.
The magnetic contactor on the
inverter's output side is properly
handled.
When using a PM motor, a low-
voltage manual contactor is
installed on the inverter's output
side.
An EMI countermeasure is
provided for the frequency setting
signals.
90
3. PRECAUTIONS FOR USE OF THE INVERTER
3.6 Checklist before starting operation
• Make sure that the terminal P/+ of the converter unit and the terminal P/+ of the
inverter, and the terminal N/- of the converter unit and the terminal N- of the
inverter are correctly connected. Connecting the opposite polarity of terminals
N/- and P/+ will damage the inverter.
Also, do not install an MCCB across the terminals P/+ and N/- (across
terminals P and P/+ or across N and N/-).
• Always connect the terminal RDA of the converter unit and the terminal MRS
(X10) of the inverter, and the terminal SE of the converter unit and the terminal
SD (terminal PC in the source logic) of the inverter. Not doing so may lead to
damage of the converter unit.
When using a switching circuit as shown below, chattering due to misconfigured
sequence or arc generated at switching may allow undesirable current to flow in
and damage the inverter. Miswiring may also damage the inverter. (The
commercial power supply operation is not available with Vector control
dedicated motors nor with PM motors.)
Power
R/L1 U
supply
S/L2 V
T/L3 W
Undesirable current
Inverter/
converter unit
If switching to the commercial power supply operation while a failure such as an
output short circuit has occurred between the magnetic contactor MC2 and the
motor, the damage may further spread.
Therefore, make sure to take precautions against such a failure, for example,
providing a protection circuit using the OH input signal.
If the machine must not be restarted when power is restored after a power
failure, provide an MC in the converter unit's input side and also make up a
sequence which will not switch ON the start signal. If the start signal (start switch)
remains ON after a power failure, the inverter will automatically restart as soon
as the power is restored.
The encoder must be directly connected to a motor shaft without any backlash.
(Real sensorless vector control or PM sensorless vector control do not require
an encoder.)
On the converter unit's input side, connect an MC for the following purposes:
• To disconnect the inverter and the converter unit from the power supply at
activation of a protective function or at malfunctioning of the driving system
(emergency stop, etc.).
• 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 and the converter unit from the power supply to ensure
safe maintenance and inspection work.
Use the converter unit 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.
Switch the magnetic contactor between the inverter and motor only when both
the inverter and motor are at a stop.
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, such as
fan and blower, where the motor is driven by the load, a low-voltage manual
contactor must be connected on the inverter's output side, and wiring and
inspection must be performed while the contactor is open. Otherwise you may
get an electric shock.
If electromagnetic noise generated from the inverter and the converter unit
causes the frequency setting signal to fluctuate and motor rotation speed to
become unstable when changing the motor speed with an analog signals, the
following measures are effective.
• Do not run the signal cables and power cables (inverter and converter unit I/O
cables) in parallel with each other, and do not bundle them.
• Run the signal cables as far away as possible from the power cables (inverter
and converter unit I/O cables).
• Use shielded cables.
• Install a ferrite core on the signal cable (Example: ZCAT3035-1330 TDK).
Countermeasure
MC1
Interlock
IM
MC2
Refer to Check by
page user
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