Thermal Protection
Technical Manual: Smartstart
®
6000
IMI0042 rev D
Page 29
Starter Thermal Protection:
Thermal protection of the soft starter is provided by a
temperature sensor located on the heatsink and by
calculating the temperature of the thyristor junction
with sophisticated modeling of the specific devices
used. Fans are powered by 24VDC supply and
thermally controlled when the heatsink temperature
exceeds 40°C and whist the motor is ramping.
Motor thermal Protection
The SS6000 provides thermal protection of the motor
by providing a thermistor input and also a
programmable motor overload protection feature.
The starter continuously monitors the current and
calculates the temperature rise of the motor based on
the motor data provided. The standard IEC60947-4-2
defines the protection classes giving the starting
capacities of the motor (warm or cold) without thermal
trips.
The thermal protection displayed by the starter
corresponds to the thermal time constant:
•
An overload trip will occur and stop the motor, if
the motor exceeds the critical temperature rise
threshold of 125%
•
This feature has a memory function based on the
thermal capacity and may not allow a start if
the temperature rise is too high.
•
The thermal state continues to calculate even
when the starter is off and powered down.
Simply by turning power off and back on will
not reset the thermal state.
Motor thermistor Protection
The SS6000 provides an input for a thermistor or
normally closed switch. Thermistor / PTC probes
integrated in the motor to measure its temperature
can be connected to the thermistor input terminals.
This input has a trip resistance of 3000ohms and a
resistance of 20ohms or less will be detected as a
short circuit.
Alternatively, a normally closed thermal switch may be
used which open circuits at a specific temperature.
Motor thermal Protection
Cold Curves
Hot Curves
SS6000 Motor Thermal Over load Cur ves - Cold
1.000
10.000
100.000
1000.000
10000.000
0
1
2
3
4
5
6
7
8
X FLC
T
ri
p
T
im
e
(
s
)
Class 30 Cold
Class 20 Cold
Class 10 Cold
Class 10A Cold
Class 2 Cold
SS6000 Motor Thermal Overload Curves - Warm
0.100
1.000
10.000
100.000
1000.000
0
1
2
3
4
5
6
7
8
X FLC
T
ri
p
T
im
e
(
s)
Class 30 Warm
Class 20 Warm
Class 10 Warm
Class 10A War m
Class 2 War m
