66 EAV64301 01/2015
Cable Length Instructions
Long Cable Lengths Consequences
When drives are used with motors, a combination of fast switching transistors and long motor cables can
even cause peak voltages up to twice the DC link voltage. This high peak voltage can cause premature
aging of motor winding insulation which leads to motor breakdown.
The overvoltage limitation function will enable to increase the cable length while decreasing the torque
performances.
Corrective Actions Overview
A number of simple measures can be taken to help enhance the motor life time:
z Specification of a motor designed for speed drive applications (IEC60034-25 B or NEMA 400 should be
prescribed).
z Specification of drives that integrate voltage reflection superimposition software suppression.
z Reduce to a minimum the distance between motor and drive.
z Use unshielded cables.
z Reduce the drive switching frequency (a reduction to 2.5 kHz is recommended.)
Preventive Measures According To IEC60034-25
The preventive measures will depend on motor characteristics and cable length.
NOTE: When calculating cable lengths for the purpose of guarding against these overvoltage situations, a
shielded cable should count as twice the length of an unshielded cable. For example, if a shielded cable is
100 m (328 ft) in actual length, it should be considered to be equal to a 200 m (656 ft) length standard cable
in the calculation.
Additional Information
Further detailed technical information is available in the following white paper An Improved Approach for
Connecting VSD and Electric Motors available on www.schneider-electric.com.
Motor cable length (unshielded cable) Motor conforming to
IEC60034-25
Motor NOT-conforming to
IEC60034-25
1 m (3 ft) < L < 50 m (164 ft) Filter not required dV/dt filter
50 m (164 ft) < L < 100 m (328 ft) Filter not required Sinus filter
100 m (328 ft) < L < 300 m (984 ft) Filter not required Sinus filter
300 m (984 ft) < L < 500 m (1640 ft) dV/dt filter Sinus filter
500 m (1640 ft) < L < 1000 m (3281 ft) Sinus filter Sinus filter
To Next Page
Loading...
