Vacon 100X series Applications Manual page 91

Parameters
6.1.10.2 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 capac-
ity. 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 spec-
ifies 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
6.1.
NOTE! If you use long motor cables (max. 100m) 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
13006.emf
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.
13006.emf
Code Parameter
P3.9.2.1 Motor Therm Prot
P3.9.2.2 MotAmbient Temp
P3.9.2.3 ZeroSpeedCooling
P3.9.2.4 ThermTimeConst
P3.9.2.5 MotThermLoadbil
Service support: find your nearest Vacon service center at www.vacon.com
Table 73. Motor thermal protection settings
Min Max
0 3
-20.0 100.0
5.0 150.0
1 200
10 150
Unit Default ID
0 = No action
1 = Alarm
2 = Fault (Stop according to
2 704 3 = Fault (Stop by coasting)
If available, use the motor
thermistor to protect the
motor. Choose then value 0
for this parameter.
°C 40.0 705 Ambient temperature in °C
Defines the cooling factor at
zero speed in relation to the
% Varies 706 point where the motor is run-
ning at nominal speed with-
out external cooling.
The time constant is the time
within which the calculated
min Varies 707
thermal stage has reached
63% of its final value.
Motor thermal Loadability
states how much the motor
can be thermally loaded. E.g.
90% means that the motor
% 100 708
temperature will settle
around 100% when continuo-
sly running at 90% of nomi-
nal load.
vacon • 88
Description
stop mode)
6