• Moderate braking provides faster deceleration compared to a situation where flux
braking is disabled. The flux level of the motor is limited to prevent excessive heating
of the motor.
• Full braking exploits almost all available current to convert the mechanical braking
energy to motor thermal energy. Braking time is shorter compared to moderate
braking. In cyclic use, motor heating may be significant.
Settings and diagnostics
Parameter: 97.5 Flux braking (page 520).
￭ DC magnetization
DC magnetization can be applied to the motor to
• heat the motor to remove or prevent condensation, or
• to lock the rotor at, or near, zero speed.
Pre-heating
A motor pre-heating function is available to prevent condensation in a stopped motor,
or to remove condensation from the motor before start. Pre-heating involves feeding a
DC current into the motor to heat up the windings.
Pre-heating is deactivated at start, or when one of the other DC magnetization functions
is activated. With the drive stopped, pre-heating is disabled by the safe torque off function,
a drive fault state, or the process PID sleep function. Pre-heating can only start after
one minute has elapsed from stopping the drive.
A digital source to control pre-heating is selected by parameter 21.14. The heating
current is set by 21.16.
Pre-magnetization
Pre-magnetization refers to DC magnetization of the motor before start. Depending on
the selected start mode (21.1 or 21.19), premagnetization can be applied to guarantee
the highest possible breakaway torque, up to 200% of the nominal torque of the motor.
By adjusting the pre-magnetization time (21.2), it is possible to synchronize the motor
start and, for example, the release of a mechanical brake.
DC hold
The function makes it possible to lock the rotor at (near) zero speed in the middle of
normal operation. DC hold is activated by parameter 21.8. When both the reference
and motor speed drop below a certain level (parameter 21.9), the drive will stop
generating sinusoidal current and start to inject DC into the motor. The current is set by
parameter 21.10. When the reference exceeds parameter 21.9, normal drive operation
continues.
68 Program features
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