PTC Thermistor Motor Starter

PTCR Motor Starter

PTCR Motor Starter

PTCR Motor start packages can be economical solid state torque assist for heat pumps, room air, commercial and residential air conditioning and refrigeration systems. PTC thermistor can be used to protect the auxiliary starter winding of induction motors or single phase motors.

When the circuit is turned on, the PTC has a low resistance and most of the line voltage is applied to the starter winding. After motor starting, the PTC heats up and switches to a high resistance state. The time for this to occur is determined by the size and resistance of the PTC, as well as the amount of current flowing through the starter winding. When the PTC has reached a high resistance state, the current flowing through it, as well as the starter winding, falls substantially.  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.

Compared to the alternative start capacitor and relay, PTCR Motor start devices save several wires, occupy less panel space, mount more easily, and cost less.

PTC Thermistor Motor Starter Pellet Application:

Single-phase motor start assist in refrigerator systems, air-conditioning systems, heat-pumps, small compressors.
Inrush current generation.

PTC Thermistor Motor Starter Features:

  • Complete range of size resistance combination for 120V, 240V compressor motors.
  • Rugged silver electrodes well suited for long life pressure contact mounting.
  • Various pellet sizes for optimum inrush current and switching time.
  • Typical resistance @25C 4.7 ohm, 6.8 ohm,15 ohm, 22 ohm, 33 ohm.

PTCR Motor Starter Operating Principles

Simple PTC thermistor starter circuit for single-phase AC motors

Simple PTC thermistor starter circuit for single-phase AC motors

Single phase induction motors (e.g in compressors for refrigerators and air conditioners) can effectively be started when an auxiliary coil is used in the starting phase. The auxiliary coil is cut off from the circuit after the starting phase. For this purpose, PTC thermistor is employed.
When high voltage is applied to the PTC thermistor, the high current causes PTC thermistor to heat up and eventually the resistance to increase. A high current flows initially (starting phase ) and then decreases in relation to the increase in resistance. After the starting phase, a low residual current flows the auxiliary coil.

The PTC thermistor is used for delaying the switch-off of the starter auxiliary winding (after the motor has accelerated) to protect the winding from damage.

PTC Current vs. Time Showing Definition Rdyn and Switch Time

PTC Current vs. Time Showing Definition Rdyn and Switch Time

PTC Thermistor Motor Starter Pellet

PTC Thermistor Motor Starter Pellet

PTC Motor Starter Pellet Construction

PTC Motor Starter Pellet Construction

AMWEI PTC Thermistor Motor Starter Pellets (Disk) Data Sheet

Resistance
R25
(ohm)
Max. Voltage
(V)
Max. Current
(A)
Starting Time
(Seconds)
Power Consumption
(W)
Recovery Time
(Seconds)
Coil Resistance
(ohm)
Switching Temperature
Centigrade
Diameter
(mm)
Thickness

(mm)

4.7 ohm180V12A0.5-2.5S3.5W100S10 ohm

120C

19.5+\-1.0
mm

2.5+\-0.2
mm

6.8 ohm200V10A0.2-1.5S3.5W100S25 ohm
15 ohm350V8A0.2-1.5S3.0W100S30 ohm
22 ohm350V7A0.2-1.5S3.0W85S30 ohm
33 ohm350V6A0.2-1.5S3.0W85S55 ohm
47 ohm400V5A0.2-1.5S3.0W75S55 ohm
4.7 ohm180V12A0.2-1.3S3.3W85S10 ohm

120C

16+\-0.5
mm

2.5+\-0.2
mm

6.8 ohm180V10A0.2-1.2S3.3W90S10 ohm
15 ohm350V8A0.2-1.2S2.8W100S30 ohm
22 ohm350V7A0.2-1.0S2.8W85S30 ohm
33 ohm350V6A0.2-1.0S2.8W85S30 ohm
47 ohm350V5A0.2-1.0S2.8W80S30 ohm

PTC Thermistor Motor Starter Reliability Data

Test
Standard
Test conditions
ΔR25/R25|
Switching test at room temperatureIEC 60738-1Imax Vmax Number of cycles: 10000<25%
Rapid change of temperature in airIEC600628-2-14, Test NaT=TLCT, T=TUCT Number of cycles: 5 T:30min<20%
Endurance at max. operating temperature and max. operating voltageIEC 60738-1Ambient temperature: +60C Maximum Operating Voltage Current limited to Imax. Time: 24 hours<25%
Storage in damp heatIEC 600628-2-3Temperature of air: 40C Relative humidity of air: 93% Duration: 56 days<20%

PTC Thermistor Motor Starter Application Examples

PTC thermistor motor starter for RSI CSIR CRS PSC motors

PTC thermistor motor starter for RSI CSIR CRS PSC motors

Motor Starting Circuit

Motor Starting Circuit

Starting Circuit with PTC Thermistor Motor Starter

Starting Circuit with PTC Thermistor Motor Starter

Other AMWEI PTC Thermistors Products for Motor Application

Linear silicon PTC thermistor

Linear silicon PTC thermistor Sensor

PTC Thermistors Current Protector

PTC Thermistors Current Protector

PTC Thermistors Motor protection Single Sensors Triple Sensors

PTC Thermistors Motor protection Single Sensors Triple Sensors