Technical data

Manual – Gear Units and Gearmotors
89
7
Circuit breakers and protective equipment
Project Planning for AC Motors
Secure switching
of inductances
Note the following notes for switching of inductances:
• Switching of low-speed motor windings.
If the cable is installed unfavorably, switching of low-speed motor windings can
generate voltage peaks. Voltage peaks can damage windings and contacts. Install
varistors in the incoming cable to avoid such problems.
• Switching of brake coils.
Varistors must be used to avoid harmful switching overvoltages caused by switching
operations in the DC circuit of disk brakes.
Brake control systems from SEW-EURODRIVE are equipped with varistors as
standard. Use contactors with contacts in utilization category AC3 or better to
EN 60947-4-1 for switching of brake coils.
• Suppressor circuit on the switching devices.
According to EN 60204 (Electrical Equipment of Machines), motor windings must be
equipped with interference suppression to protect the numerical or programmable
logic controllers. Because problems are primarily caused by switching operations,
we recommend installing suppressor circuits on the switching devices.