PTC Thermistor Motor Sensor
PTC Thermistors Motor Sensor is ceramic PTC Thermistor pellet with insulated wire cable, used for motor temperature sensing and over-temperature protection, by using PTC thermistor characteristics resistance rises sharply at Curie temperature.
PTC Thermistors Motor Temperature Sensors with their very steep curves are very suitable for the monitoring of temperature limits and consequently for switching on a fan when a particular temperature is reached.
PTC Thermistor Motor Temperature Sensors are designed to provide economic and reliable overtemperature protection for three-phase motors. This assembly utilizes a small PTC disk that has a low base resistance. Once the motor winding temperature reaches the trip temperature of the PTC thermistor, its resistance increases several orders of magnitude for a small increase in temperature. This sharp increase in resistance is easily recognized by the motor protection module or other electronics and can be used to shut down the system before any damage occurs.
PTC assemblies are very small and rugged, they can be located in compact locations where protection is needed, such as directly inside the motor windings and can withstand standard varnish dip and bake operations, and other handling.
A further advantage of the PTC thermistor temperature characteristic is that PTC thermistors can be connected in series and thus, in their function as temperature sensors, can very easily monitor several hot spots. As soon as one of these PTC thermistors sensors in a series connection exceeds the specified limit temperature, the circuit switches to the high-ohmic state.
A further application of PTC thermistor sensors is the thermal monitoring of the windings in three-phase motors. For this purpose, AMWEI offers special types that are assembled accordingly and which can be easily integrated into the windings.
PTC thermistors, Sleeve Type for Over-Temperature Protection, intended for over-temperature sensing of windings in electric motors, coils, transformers, equipment, machines, etc.
Available as 1 PTC single sensor & 3 PTC in series triple sensors.
·Thermal protection of winding in electric motors.
·Limit temperature monitoring.
·PTC relay units.
·Electronic data processing.
·Electric equipment machines.
·PTC thermistor pellet with insulating encapsulation
·Low resistance type, steep R/T curve.
·Fast response due to small dimensions.
·Characteristics for sensing temperatures conform with DIN 44081 for 1 PTC single sensor, DIN 44082 for 3 PTC in series triplet sensors.
·No need to reset supply after over-temperature switch.
·For 1 PTC single sensor, color coding of litz wires to DIN 44081. For 3 PTC in series triplet sensors, color coding of litz wires to DIN 44082, connecting wires in yellow.
The PTC thermistor sensor is mounted in thermal contact with the equipment to be protected, and connected into the bridge arm of a comparator circuit, such as shown in Fig.1.
At normal temperature, the PTC thermistor resistance (Rp) is lower than Rs (see Fig.2), so the comparator’s output voltage VO will be low.
If an equipment over temperature occurs, the PTC thermistor sensor will quickly heat up to its trigger or nominal reference temperature Tn, whereupon its resistance will increase to a value much higher than Rs, causing VO to switch to a high level sufficient to activate an alarm, relay or power shutdown circuit.
PTC Thermistor in Comparator Circuit Diagram
Typical Switch Characteristic Graph
Thermistor Temperature Protection of 3 Phase Electric Motor
PTC Thermistor Motor Protection 1 PTC Single Sensor Dimension (Unit :mm)
PTC Thermistor Motor Protection 3 PTCs Triple Sensor Dimension (Unit :mm)
Note: The Intermediate connection wire is in yellow color.
PTC Thermsitor Motor Protection
A single or triple protection sensor is included into the winding of the motor. When at least 1 sensor gets high ohmic due to over-temperature, the tripping unit switches off the motor.