Flux Braking; Thermal Motor Protection - ABB ACSM1 Firmware Manual

Flux braking

The drive can provide greater deceleration by raising the level of magnetization in
the motor. By increasing the motor flux with
generated by the motor during braking can be converted to motor thermal energy.
Motor
speed
Flux braking
The drive monitors the motor status continuously, also during flux braking.
Therefore, flux braking can be used both for stopping the motor and for changing the
speed. The other benefits of flux braking are:
• The braking starts immediately after a stop command is given. The function does
not need to wait for the flux reduction before it can start the braking.
• The cooling of the induction motor is efficient. The stator current of the motor
increases during flux braking, not the rotor current. The stator cools much more
efficiently than the rotor.
• Flux braking can be used with induction motors and permanent magnet
synchronous motors.
Two braking power levels are available:
• 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.

Thermal motor protection

With the parameters in group 45, the user can set up the motor overtemperature
protection and configure motor temperature measurement (if present). This block
also shows the estimated and measured motor temperature.
The motor can be protected against overheating by
• the motor thermal protection model
• measuring the motor temperature with PTC or KTY84 sensors. This will result in a
more accurate motor model.
T
T
No flux braking
t (s)
40.10 FLUX BRAKING, the energy
Br
T
(%)
Br
T = 100 Nm
N
N
60
40
Flux braking
20
No flux braking
Drive control and features
= Braking torque
f (Hz)
41