Mitsubishi Electric FR-E700 Installation Manuallines page 11

3.3.2 Maximum permissible motor wiring length
The maximum permissible length of the motor cables depends on the capacity of the inverter and the selected carrier
frequency.
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.
Setting of Pr. 72 PWM Frequency selection
(carrier frequency)
1 (1kHz) or less
2 to 15 (2kHz to 14.5kHz)
Total wiring lenght (FR-E740-095 or more)
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.
Carrier frequency
Limiting the voltage rise speed of the frequency inverter output voltage (dU/dT):
If the motor requires a rise speed of 500V/μs or less you must install a filter in the output of the inverter. Please contact
your Mitsubishi dealer for more details.
CAUTION
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 stall prevention 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. When stall prevention function misoperates,
increase the stall level. (For Pr. 22 Stall prevention operation level and Pr. 156 Stall prevention operation selection, refer to the Instruction
Manual.)
For details of Pr. 72 PWM frequency selection, refer to the Instruction Manual.
When using the automatic restart after instantaneous power failure function with wiring length exceeding 100m, select without
frequency search (Pr. 162 = "1, 11"). (Refer to the Instruction Manual).
016
200m
30m
≤ 50m
50m–100m
≤ 14.5kHz ≤ 8kHz
026 040
200m 300m
100m 200m
500m or less
300m
300m
300m + 300m = 600m
≥ 100m
≤ 2kHz
WIRING
≥ 095
060
500m 500m
300m 500m
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