Temperature Sensors - Tecnotion TM3 Series Manual

3.5

Temperature sensors

The coil unit is equipped with two temperature sensors, one PTC-1k-type
and one KTY83-122 type.
The temperature sensors are normally used for overheating protection of
the coil unit. The KTY-sensor can be used for monitoring temperature, the
PTC can be used as cut off sensor when the maximal temperature is ex-
ceeded. For specifications and characteristics see the next two paragraphs.
In cases where long peak currents are demanded, the thermal response
time of the coil unit is too long to ensure a proper overheating protection
by the sensors. The temperature sensors can ensure a proper protection up
to an Irms of 45% of the ultimate current of the motor. This corresponds to
a temperature increase of 4,5°C/s.
These long peak current conditions can occur for example during an acci-
dental run or by taking a new axis in control.
In this case I²t protection is essential to prevent the coil unit from overhe-
ating. In almost all controllers an I²t-protention can be set in the software.
For more information contact Tecnotion's Application support team.
PTC characteristic
The PTC-1k type is a sensor which has a very sudden resistance rise near
the critical temperature of the coils at 110°C . It is almost a digital indicator:
temperature below vs. above critical temperature. Therefore it is very use-
ful for signaling critical temperature without requiring sensitive electro-
nics. It is not possible to obtain a direct temperature signal from this sensor.
©2015 Tecnotion BV - All rights reserved - The contents of this document are subject to change without prior notice.
At room temperature the PTC has an electrical resistance <100 Ω. When
the temperature raises to the critical temperature the resistance will incre-
ase rather uniformly up to 1000 Ω. Above this temperature the resistance
increases exponentially. 1000 Ω is the switching resistance. The amplifier
should immediately stop the power supply when this resistance is excee-
ded. In this way overheating and motor damage can be prevented.
R ( )
10 7
10 6
10
5
10 4
10
3
10
2
10 1
10 30 50 70 90 110
Graph 3.21: Temperature dependence of the PTC-1k sensor.
CH 3 MOTOR CONFIGURATION
T (°C)
180
130 150
21