Siemens SINAMICS PERFECT HARMONY GH180 - 10.3 Safe VFD Power Down and Door Access

4.7.10 Synchronous Motor with DC Brushless Exciter (SMDC)
Synchronous Motor with DC Brushless Exciter (SMDC) control is used for all applications with
synchronous motors (SMs) that have a brushless DC exciter. Unlike SMs with an AC exciter, SMs
with a brushless DC exciter require a di󹪜erent starting strategy to pull the motor into
synchronization.
For normal SM operation with brushless AC excitation, the full 󹪞ux is already established when
the VFD starts. The DC exciter cannot provide any main 󹪝eld current, and hence the 󹪞ux, when
at standstill. To start such a machine, the VFD applies a high starting torque current with a
slowing rotating vector, to align enough with the rotor poles to begin magnetization of the
motor. When alignment begins, the motor shaft will begin to spin. Once the motor is rotating,
the drive will pull the motor into synchronization and transition to normal SMC.
Startup is based on the high starting torque method already implemented in the control code.
It adds a separate starting state machine that requires only the selection of SMDC control mode.
High starting torque mode is set internally and automatically.
Once operational, the machine will continue in operation as a standard SM. Spinning load and
fast bypass cannot be used in this control mode, these features are disabled internally.
NOTICE
Potential Damage to Motor
If the motor does not come to a complete stop before restarting it may result in higher than
rated torque on the motor and shaft, and lead to damage to the motor or load.
Ensure that the motor has come to a complete stop before restarting.
Parameter Settings for SMDC
The parameters associated with this control mode are detailed in Sections Drive Menu (2)
Options and Motor Menu (1) Options of Chapter Parameter Assignment / Addressing. These
parameters are:
• Control loop type (2050) in the Drive Parameter Menu (2000)
• Max DC Exciter Curr (1105) in the Motor Parameter Menu (1000)
• Initial Mag Current (1106) in the Motor Parameter Menu (1000)
NXGPro+ Control Description
4.7 Control Modes
NXGPro+ Control Manual
Operating Manual, A5E50491925A 59