Refrigerators Frequency Converters Motor Overheat Protection PTC Thermistor MZ3

Product Specification

Refrigerators Frequency Converters Motor Overheat Protection PTC Thermistor MZ3-B-47ROM for Motor Starter in Air Conditioner

Product advantages

The starting circuit with PTCR is economical, reliable and simple in design. It outperforms the previous hammer-type starting circuit and features contactless operation, low noise, high reliability and long service life.

Motor start-up type thermistor Description
Positive temperature coefficient thermistors for motor starting are mainly used for starting motors in refrigerators and air conditioners, starting air conditioner frequency converters, and motor overheat protection, etc.
Working principle The motor starter utilizes the current-time characteristic of PTC ceramic. When voltage is applied to the PTCR, a large current I begins to flow through. After a certain period of time ts, as the temperature of the PTCR rises, the resistance value increases rapidly, causing the current to drop sharply. During this period, ts can range from 0.1 seconds to several seconds. Its value depends on the heat capacity, resistance value, heat dissipation conditions, load resistance and working voltage of the PTCR. When the external voltage is removed, the PTCR will cool to the resistance value at room temperature. Based on this principle, it has been widely applied in the motor starting of household appliances such as refrigerators and air conditioners. It should be noted that when using the delay performance of PTCR, if the same delay time is to be repeated, a certain interval time tr (i.e., the so-called recovery time) should be set to allow the PTCR to return to its original state temperature. Therefore, immediate repetitive actions should be avoided; otherwise, the PTCR cannot provide a continuous large current, causing the compressor to fail to start working normally and potentially leading to compressor burnout.
When a motor starts, it needs to overcome its own inertia and also the reaction force of the load (for example, when a refrigerator compressor starts, it must overcome the reaction force of the refrigerant). Therefore, a large current and torque are required for the motor to start. When the rotation is normal, in order to save energy, the required torque will drop significantly again. Add a set of auxiliary coils to the motor, which only work during startup and disconnect once it operates normally. Connect the PTC thermistor in series with the starting auxiliary coil. After starting, the PTC thermistor enters a high-resistance state and cuts off the auxiliary coil, which can precisely achieve this effect.
Product advantages: The starting circuit with PTCR is economical, reliable and simple in design. It outperforms the previous hammer-type starting circuit and features contactless operation, low noise, high reliability and long service life.

Specification of MZ3-B-47ROM

What Is PTC Thermistor Motor Starter ?

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

PTC Thermistor Motor Starter 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,47 ohm.