Electrical Design
‑48‑
Motor Cable Length Requirements
During operation of the AC drive, large dU/dt is generated on the output side due to
the fast on‑off of the power switching tube. When the motor cable is too long, a large
voltage stress will be generated on the motor winding, causing insulation breakdown.
It is highly recommended to use motors that comply with IEC60034‑25 IVIC B or use
motors with high insulation withstand voltage. In addition, with the increase of cable
length, the distributed capacitance of the cable increases linearly, which is easy to
generate higher harmonic current.
When the length of the motor cable is greater than the maximum length
recommended in the following table, install an output reactor on the output side of
the drive, or use a motor conforming to IEC60034‑25 IVIC B. The output reactor can
reduce the voltage stress on the motor winding.
Table 3–7 Output Reactor Cable Length and Motor Type
AC Drive Rated
Power (kW)
Maximum Cable
Length for Common
Asynchronous Motor
(m)
IEC60034‑25 IVIC B
Compliant
Common
asynchronous
induction motor
0.4 to 3.7 150 m
Not required Required
5.5 150 m
Not required Required
7.5 150 m
Not required Required
Motor Output Cable Requirements
Perform the following operations to make the motor output cable. (Take MD800 dual‑
axis drive unit as an example.)
1. Strip the cable rubber jacket and shielding layer according to the following length
requirements.
2. Turn the shielding layer outward or wrap it three turns with conductive tape.
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