Synchronous Motor Control (Smc) - Siemens SINAMICS PERFECT HARMONY GH180 Function Manual

NXGPro+ Control Description
4.7 Control Modes
4.7.6

Synchronous Motor Control (SMC)

For synchronous motor control (SMC), the drive is equipped with a field exciter that usually
consists of a SCR based current regulator. The field exciter operates to maintain a field current
level that is commanded by the flux regulator. An example application for a brushless
synchronous motor is shown in the figure below.
Figure 4-5 Drive Arrangement for Synchronous Motor with AC Brushless Exciter
The figure shows a brushless synchronous motor with the static exciter wound for 3-phase AC in
the range of 350 to 400 volts. If this is not the case, then a transformer is needed between the
auxiliary power and the field exciter. The circuit wheel needs only a rectifier.
Motor Protection
The control provides for minimal motor protection when the motor is connected to the drive. For
a system that employs drive, not cell, bypass, external protection of the motor is required. The
control will trip the drive on a loss of field fault if the motor draws excessive reactive current,
which will occur when the exciter fails full on or off. An external means to disconnect the exciter
power from the field is required to fully protect the motor.
Flux regulator implementation
The overall control strategy is similar to OLVC, except for the flux regulator implementation.
Refer to Figure Vector Control Algorithms. For synchronous motors, the flux regulator provides
two current commands, one for the field exciter current, and another for the magnetizing
component of stator current.
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NXGPro+ Control Manual
Operating Manual, A5E50491925A