PTC Thermistors Limit Temperature Sensors for Motor Protection 1 PTC Single Sensor & 3 PTC Triple Sensors

What Is PTC Thermistor Motor Sensor？

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.

PTC Thermistors Motor Sensor Application

·Thermal protection of winding in electric motors.
·Limit temperature monitoring.
·PTC relay units.
·Industrial electronics.
·Power supplies.
·Electronic data processing.
·Electric equipment machines.

Features of PTC Thermistors Limit Temperature Sensors for Motor Protection

·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.

PTC Thermistors Motor Sensors Operating Principle

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 Thermistors Motor Sensor Dimension

PTC Thermistor Motor Protection 1 PTC Single Sensor Dimension (Unit :mm)

PTC Thermistor Motor protection 3 PTC triple Sensor Dimension

PTC Thermistor Motor Protection 3 PTCs Triple Sensor Dimension (Unit :mm)

AMWEI PTC Thermistors Motor Senor General Data Sheet

Max. operating voltage	Vmax	30V
Max. measuring voltage	Vmeas, max	2.5V
Rated resistance (2.5V max)	R25	≤100 ohm
Insulating test voltage	Vins	2.5kV
Ts trip time	t	≤5 Seconds
Ts Sensing temperature tolerance	ΔT	±5C
Max. Operating temperature range (V≤Vmeas,max)	Top	200C

AMWEI PTC Thermistor Motor protection 1 PTC Single Sensor Data Sheet

Sensing Temperature T_sense Centigrade	Resistance @25C R₂₅ （Ohm）	Resistance @ Tsense-5C R_sense-5 （Ohm）	Resistance @ T_sense+5C R_sense+5 （Ohm）	Resistance @ T_sense+15C R_sense+15 （Ohm）	Wire Color	AMWEI Part No.
90C	≤100 Ohm	≤550 Ohm	≥1330 Ohm	≥4k ohm	Green/Green	AMZ6-MT90C1
100C	≤100 Ohm	≤550 Ohm	≥1330 Ohm	≥4k ohm	Red/Red	AMZ6-MT100C1
110C	≤100 Ohm	≤550 Ohm	≥1330 Ohm	≥4k ohm	Brown/Brown	AMZ6-MT110C1
120C	≤100 Ohm	≤550 Ohm	≥1330 Ohm	≥4k ohm	grey/grey	AMZ6-MT120C1
130C	≤100 Ohm	≤550 Ohm	≥1330 Ohm	≥4k ohm	blue/blue	AMZ6-MT130C1
140C	≤100 Ohm	≤550 Ohm	≥1330 Ohm	≥4k ohm	white/blue	AMZ6-MT140C1
150C	≤100 Ohm	≤550 Ohm	≥1330 Ohm	≥4k ohm	black/black	AMZ6-MT150C1
160C	≤100 Ohm	≤550 Ohm	≥1330 Ohm	≥4k ohm	Blue/Red	AMZ6-MT160C1

AMWEI PTC Thermistors Motor Protection 3 PTCs Triple Sensor Data Sheet

Sensing Temperature T_sense Centigrade	Resistance @25C R₂₅ （Ohm）	Resistance @ Tsense-5C R_sense-5 （Ohm）	Resistance @ T_sense+5C R_sense+5 （Ohm）	Resistance @ T_sense+15C R_sense+15 （Ohm）	Wire Color	AMWEI Part No.
90C	≤300 Ohm	≤1650 Ohm	≥3990 Ohm	≥12k ohm	Green/Green	AMZ6-MT90C3
100C	≤300 Ohm	≤1650 Ohm	≥3990 Ohm	≥12k ohm	Red/Red	AMZ6-MT100C3
110C	≤300 Ohm	≤1650 Ohm	≥3990 Ohm	≥12k ohm	Brown/Brown	AMZ6-MT110C3
120C	≤300 Ohm	≤1650 Ohm	≥3990 Ohm	≥12k ohm	grey/grey	AMZ6-MT120C3
130C	≤300 Ohm	≤1650 Ohm	≥3990 Ohm	≥12k ohm	blue/blue	AMZ6-MT130C3
140C	≤300 Ohm	≤1650 Ohm	≥3990 Ohm	≥12k ohm	white/blue	AMZ6-MT140C3
150C	≤300 Ohm	≤1650 Ohm	≥3990 Ohm	≥12k ohm	black/black	AMZ6-MT150C3
160C	≤300 Ohm	≤1650 Ohm	≥3990 Ohm	≥12k ohm	Blue/Red	AMZ6-MT160C3

Note: The Intermediate connection wire is in yellow color.

PTC Thermsitor Motor Winding 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.