Monitoring functions and protective functions
9.5 Thermal motor protection
Drive functions
640 Function Manual, 11/2017, 6SL3097-4AB00-0BP5
The thermal motor protection monitors the motor temperature and responds to
overtemperature conditions with alarms or faults. The motor temperature is either measured
with sensors in the motor, or is calculated without sensors, using a temperature model from
the operating data of the motor. Combinations of temperature measurement and taking into
consideration a motor temperature model are possible. As soon as critical motor
temperatures are determined, measures to protect the motor are initiated.
For thermal motor protection with temperature sensors, the motor temperature is directly
measured in the motor windings. The temperature sensors are either connected to the
Control Unit, the Motor Module or supplementary modules. The determined temperature
values are sent to the Control Unit, which then responds according to the parameter settings.
When switching on again after a power failure, the actual motor temperatures are
immediately available.
With thermal motor protection without temperature sensors, different thermal motor models
are used for calculation. The temperatures according to the motor temperature model are
calculated from the motor operating data. Whereby, the masses of the motor parts and the
type of ventilation, for the I
2
t model (for synchronous motors), the motor current in relation to
the operating time is taken into consideration in the calculation. For motor temperature
protection without temperature sensor, p0600[0...n] is set to 0, p0612.00 to 1 and p0612.01
to 1.
If you are using motors from the motor lists, or with integrated DRIVE-CLiQ connection, the
relevant motor data is automatically transferred to the Control Unit.
In the control type "Vector Control", using p0610 the reaction of the drive to a detected motor
overtemperature can be parameterized. The motor may either be switched off immediately –
or continue to operate at reduced power, reduced load, under adapted conditions.
Motor temperature measurements using temperature sensors protect the motor against
overheating. If temperature sensors are not being used, then instead, the thermal motor
model can be used as motor protection. Thermal motor models respond more dynamically
than temperature sensors, and therefore provide better protection relating to brief overload
conditions.
Depending on the particular temperature model, the temperature rise is either assigned to
various motor parts (stator, rotor) or is calculated from the motor current and the thermal
time constant. A combination of thermal motor model with additional temperature sensors
can also be used.
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