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Motor start PTC thermistor application principle

Date: 2018-03-27
Viewed: 19
案例名称: Motor start PTC thermistor application principle

Application principle


When the motor starts, it must overcome its own inertia, and at the same time overcome the reaction force of the load (such as the refrigerant reaction must overcome the reaction force of the refrigerant when the refrigerator compressor starts), so the motor needs a large current and torque when starting. When the rotation is normal, in order to save energy, the required torque has to be greatly reduced. Add a set of auxiliary coils to the motor, only work at startup, and it will open after normal. Connect the PTC thermistor in series to start the auxiliary coil. After starting, the PTC thermistor enters the high-impedance cut-off auxiliary coil, which can achieve this effect.

电机启动PTC热敏电阻应用原理

Electronic ballast, energy-saving lamp preheating soft start PTC thermistor


external structure

电机启动PTC热敏电阻应用原理

Application principle


The PTC thermistor is used on the electronic ballast of the energy-saving lamp, and the hard start of the electronic ballast and the electronic energy-saving lamp can be changed to preheating start without directly changing the line to connect the product directly across the resonant capacitor of the lamp tube. The preheating time of the filament is 0.4-2.0 seconds, which can extend the life of the lamp more than four times.


The PTC thermistor is used to realize the preheating start as shown in the following figure: When the switch is turned on, Rt is in the normal temperature state, its resistance value is far lower than the resistance value of C2, and the current passes through C1, Rt to form a loop preheating filament. After about 0.4-2 seconds, the Rt Joule heat temperature exceeds the Curie temperature Tc and jumps into the high resistance state. The resistance value is much higher than the C2 impedance. The current forms a loop through C1 and C2 to cause L resonance, which generates a high voltage lighting lamp.


For a particular electronic ballast or electronic energy-saving lamp, the larger the PTC resistance value, the smaller the volume, and the lower the Curie temperature, the smaller the power consumption and the shorter the warm-up time; The greater the power consumption, the longer the warm-up time.

电机启动PTC热敏电阻应用原理

Electronic energy-saving lamp preheating soft start circuit diagram


Use attention


1. The company has a wide range of products, and the products with Curie temperature of 75 °C, 85 °C, and 105 °C are currently the most popular.


2. In addition to the specifications listed in the above table, PTC thermistors of different sizes, switching temperatures, resistance values and withstand voltage can be designed according to user requirements.


3. PTC thermistor has obtained six toxic and hazardous substance content SGS test reports on ROHS restrictions.


Electronic ballast, energy-saving lamp soft start PTC thermistor selection guide


Based on increasing the delay time, it can be achieved by increasing the Curie temperature and volume, reducing the resistance, etc., and determining the following basic principles:


1. When the energy-saving lamp works, the temperature inside the lamp is high, and the Curie temperature of the PTC thermistor should not be too low, otherwise the delay time is too short, and the preheating effect is not obtained, and the Curie temperature is above 100 °C;


2. When the starting line is a single capacitor, the PTC thermistor has a higher withstand voltage requirement, usually above 800V;


3. The PTC thermistor with high resistivity can be greatly improved in reliability, and should be preferred under the premise of satisfying the startup characteristics;


4. The situation at low temperature start-up must be considered. At low temperatures, the thermal balance resistance of the PTC thermistor is correspondingly low, which may cause the lamp to not start;


5. The switching life of the PTC thermistor is preferably greater than 100,000 times;


6. The warm-up time cannot be less than 0.4 seconds;


7. After the startup is completed, the power consumption of the PTC thermistor should comply with the relevant regulations.


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