vacon • 112 Parameters
Local contacts: https://www.danfoss.com/en/contact-us/contacts-list/
7.1.10.2 Group 3.9.2: Motor Therm Prot
The motor thermal protection is to protect the motor from overheating. The AC drive is capable of
supplying higher than nominal current to the motor. If the load requires this high current there is a
risk that the motor will be thermally overloaded. This is the case especially at low frequencies. At
low frequencies the cooling effect of the motor is reduced as well as its capacity. If the motor is
equipped with an external fan the load reduction at low speeds is small.
The motor thermal protection is based on a calculated model and it uses the output current of the
drive to determine the load on the motor.
The motor thermal protection can be adjusted with parameters. The thermal current IT specifies
the load current above which the motor is overloaded. This current limit is a function of the output
frequency.
The thermal stage of the motor can be monitored on the control keypad display. See chapter 7.1.
NOTE! If you use long motor cables (max. 100 m) together with small drives (≤1.5 kW)
the motor current measured by the drive can be much higher than the actual motor
current due to capacitive currents in the motor cable. Consider this when setting up
the motor thermal protection functions.
CAUTION! The calculated model does not protect the motor if the airflow to the motor
is reduced by blocked air intake grill. The model starts from zero if the control board
is powered off.
Table 87. Motor thermal protection settings
Code Parameter Min Max Unit Default ID Description
P3.9.2.1 Motor Therm Prot 0 3 2 704
0 = No action
1 = Alarm
2 = Fault (Stop according to stop
mode)
3 = Fault (Stop by coasting)
If available, use the motor therm-
istor to protect the motor. Choose
then value 0 for this parameter.
P3.9.2.2 MotAmbient Temp -20.0 100.0 °C 40.0 705 Ambient temperature in °C
P3.9.2.3 ZeroSpeedCooling 5.0 150.0 % Varies 706
Defines the cooling factor at zero
speed in relation to the point
where the motor is running at
nominal speed without external
cooling.
P3.9.2.4 ThermTimeConst 1 200 min Varies 707
The time constant is the time
within which the calculated ther-
mal stage has reached 63% of its
final value.
P3.9.2.5 MotThermLoadbil 10 150 % 100 708
Motor thermal Loadability states
how much the motor can be ther-
mally loaded. E.g. 90% means
that the motor temperature will
settle around 100% when contin-
uosly running at 90% of nominal
load.
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