7
WIRING
3.3.2 Maximum permissible motor wiring length
The overall wiring length for connection of a single motor or multiple motors should be within 500m. (The wiring length
should be 100m maximum for vector control.)
The lengths in the following table are for unshielded cables. When shielded cables are used divide the values listed in the
table by 2. Note that the values are for the total wiring length – if you connect more than one motor in parallel you must
add the lengths of the individual motor cables.
Note that the motor windings in three-phase AC motors are subject to far more stress when operated via frequency
inverters than with mains operation. The motor must have been approved by the manufacturer for operation on a
frequency inverter.
In the PWM type inverter, a surge voltage attributable to wiring constants is generated at the motor terminals. Especially
for a 400V class motor, the surge voltage may deteriorate the insulation. When the 400V class motor is driven by the
inverter, consider the following measures:
Use a "400V class inverter-driven insulation-enhanced motor" and set frequency in
Pr. 72 PWM frequency selection
according to wiring length.
Limiting the voltage rise speed of the frequency inverter output voltage (dU/dT):
If the motor requires a rise speed of 500V/
µ
s or less you must install a filter in the output of the inverter. Please contact
your Mitsubishi dealer for more details.
3.3.3 Cable size of the control circuit power supply (terminal R1/L11, S1/L21)
Terminal screw size: M4
Cable size: 0.75mm² to 2mm²
Tightening torque: 1.5Nm
≤
50m
50m–100m
≥
100m
Carrier frequency
≤
14.5kHz
≤
9kHz
≤
4kHz
CAUTION
Especially for long-distance wiring, the inverter may be affected by a charging current caused by the stray capacitances of the wiring,
leading to a malfunction of the overcurrent protective function or fast response current limit function or a malfunction or fault of the
equipment connected on the inverter output side. If fast response current limit function malfunctions, disable this function. (For
Pr. 156
Stall prevention operation selection
, refer to the Instruction Manual.)
For details of
Pr. 72 PWM frequency selection
, refer to the Instruction Manual.
≤
500m
300m
300m
300m + 300m = 600m
Total wiring lenght
