9
WIRING
3.2.2 Total wiring length
The maximum possible length of the motor cables depends on the capacity of the inverter and the selected carrier fre-
quency.
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 invert-
ers 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 400 V class motor, the surge voltage may deteriorate the insulation. When the 400V class motor is driven by the
inverter, consider the following measures:
앫
Use a "400V class inverter-driven insulation-enhanced motor" and set frequency in Pr. 72
PWM frequency selection
according to wiring length.
앫
Limiting the voltage rise speed of the frequency inverter output voltage (dV/dT):
If the motor requires a rise speed of 500 V/μs or less you must install a filter in the output of the inverter. Please contact
your Mitsubishi dealer for more details.
3.2.3 Cable size of the control circuit power supply (terminal R1/L11, S1/L21)
앫
Terminal screw size: M4
앫
Cable size: 0.75mm
2
to 2mm
2
앫
Tightening torque: 1.5N·m
Pr. 72
PWM frequency selection
setting
(carrier frequency)
00023
00038
00052 or more
2 (2kHz) or less
300m
500m
500m
3 (3kHz), 4 (4kHz)
200m
300m
500m
5 (5kHz) to 9 (9kHz)
100m
10 (10kHz) or more
50m
Note
앫
For the 01800 or more, the setting range of
Pr. 72 PWM frequency selection
is "0 to 6".
Wiring Length
≤
50 m
50 m–100 m
≥
100 m
Carrier frequency
≤
14.5 kHz
≤
9 kHz
≤
4 kHz
CAUTION
앫
Especially for long-distance wiring (particularly when employing shielded motor cables), 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.
When the fast-response current limit function malfunctions, make the function invalid. (For Pr.156
Stall prevention
operation selection
, refer to the Instruction Manual (applied).)
앫
For details of Pr. 72
PWM frequency selectio
n, refer to the Instruction Manual (applied).
