Siemens SINAMICS PERFECT HARMONY GH180 Function Manual page 246

Advanced Operating Functions
8.9 Dual-Frequency Braking
With DFB, motor protection is required and is applied as follows:
1. Torque pulsations:
– DFB can subject the motor to as much as 1 per unit torque pulsation at the pulsation
2. Motor heating:
– The losses generated during DFB cause motor heating and limit the number of
Pulsation Frequency
The second set of voltage vectors creates a counter-rotating flux vector that produces high slip
in the machine and generates these additional losses in the motor. You can adjust the pulsation
frequency via a menu setting as to avoid critical frequencies i.e., mechanical resonances. The
injection frequency is always in opposite rotation to the electrical frequency applied to the motor
i.e., speed and direction of the machine.
Note
Programming the pulsation frequency
Select parameter Pulsation frequency (3370) to program the pulsation frequency via the
control. This parameter provides a reference to produce the desired additional braking for the
system. Adjust this parameter setting to avoid resonance in the system.
Effects of added voltage vectors VA1 and VA2 on DFB
The voltage vectors, normal VA1 and loss-inducing VA2, are added together to produce the
braking function.
244
frequency. Select the torque pulsation frequency via the menu entry for pulsation
frequency to avoid any mechanical resonance frequencies.
deceleration ramps from full speed to zero, that can be performed repetitively. Motor
heating due to the additional losses is designed to be no worse than a line start.
The software motor thermal model in the control monitors motor heating and provides
an alarm and/or a trip to indicate excessive heating. Refer to Section Motor Thermal
Overload Protection for information on the thermal model. The number of repetitive
deceleration ramps, from full speed to zero, is limited to two per hour. This limitation is
based on MG-1, Part 20, which assumes that the motor has cooled down to its rated
temperature before the second ramp down. It applies when the load inertia and load
torque are those for which the motor is designed. You can use DFB more frequently with
lower values of load inertia and/or smaller speed reductions.
NXGPro+ Control Manual
Operating Manual, A5E50491925A