application method and precautions of thermal protector in overheating and overload protection of electric motor and motor。
With the development of technology, the application range of electric motors is becoming more and more extensive, especially the use of electric motors in daily life and production is becoming more and more important. Electricity is an indispensable part in many applications, and accidents that cause motor burnout also occur from time to time. In real life, motor burnout is mainly caused by the following reasons.
1. Motor heating
The main feature of motor burnout is heat generation, and the reason for motor burnout is due to the heating of the stator winding, the heating and cooling of the motor is a rather slow process of change, therefore, the motor embedded thermal protector can achieve effective protection.
2. Motor overload
The motor sometimes stalls, overloading the motor and burning it. Therefore, it is necessary to implement inverse time characteristic protection for motor overload, which is generally completed by overcurrent relays or thermal relays.
3. Motor phase failure
Most of the damage to the motor is caused by the lack of phase. Motor burnout faults caused by phase loss account for 80% of the total motor burnout. For a long time, the general view is that the operation of the motor without phase operation will cause the motor winding to be overheated and damaged. It is believed that the use of the temperature rise of the thermal protector is the most direct and effective method of protection against phase loss. However, the actual situation is that if the motor operates without phase Burnt out in a very short time. Relying on the traditional inverse time characteristic protection or the method of monitoring the temperature cannot protect the phase loss of the motor.
The function of the motor thermal protector is to comprehensively protect and control the overcurrent thermal overload of the motor. When overheating, grounding, bearing wear, stator and rotor eccentricity, and winding aging, alarm or protection control is given.
How does the thermal protector protect the motor? Thermal protector, also called temperature switch, temperature control switch, etc. It is a temperature switch that uses a bimetallic sheet as a temperature sensing element. When the electrical appliance is working normally, the bimetallic sheet is in a free state and the contacts are in a closed/disconnected state. When the temperature rises to the operating temperature value, the bimetallic element is heated. Generate internal stress and act quickly, open/close contacts, cut/connect the circuit, and thus play a role in thermal protection. An's electronic ST01 thermal protector is the first pure temperature temperature switch in China that has obtained dual certifications of UL and TUV. When the circuit is turned on, the current does not pass through the dual plates, there is no current heating effect, and the temperature control is more accurate.
The connection method between thermal protector and motor: three-phase motor star connection
Because many motor manufacturers use the vacuum dipping production process to ensure coil insulation. After repeatedly improving the process and purchasing high-efficiency vacuuming equipment, the thermal protector produced by Andi Electronics has achieved extremely high sealing performance. In the case of -0.09MP, the dipping rate can reach 3‰, which can prevent the vacuum dipping process. Product fails. Reduce the failure rate of thermal protector due to vacuum dipping to less than one thousandth, becoming the product with the lowest defect rate in the industry.
Andi's electronic saftty ST01 small-volume thermal protector adopts metal casing, can withstand 50KG coil shaping pressure, has good thermal conductivity, and is sensitive to temperature. It is suitable for binding on the surface of enameled wire or embedded in the motor coil. The operating temperature can be set at 60 ℃ Between -180℃.
heat protector
Supporting technology:
• Integrate global supply chain resources, the double-piece adopts the material of US EMS, the world's largest double-piece manufacturer, and the outer shell adopts the stamping and forming technology of the German supplier.
• The reeds are made of Japanese NGK materials and are processed and produced by Japanese stamping parts suppliers.
• The housing and reed are silver-plated, which greatly reduces contact resistance.
• Double-piece core components are produced and tested by fully automatic molding equipment and temperature screening tunnel kiln, with good consistency and stable performance.
Matters needing attention in the use of thermal protectors for motors:
1. The thermal protector can only be used under the specified rated voltage, current and specified temperature to ensure that the basic parameters of the protector meet the design requirements.
2. When the lead wire of the thermal protector is bent and used, it should be bent at a distance of more than 10 mm from the root of the protector, and cannot forcibly pull, twist or lead.
3. The print of the thermal protector model is literally a non-temperature sensitive surface. During assembly, the temperature-sensitive surface should be attached to the heating surface of the protected device for temperature sensing.
4. The metal shell of the thermal protector can be charged, and the shell needs to be insulated during installation. When using our products with insulating sheath, it is strictly forbidden to pierce the insulating sheath with sharp or sharp metal to prevent insulation failure.
5. During plastic assembly, the maximum allowable static pressure of the product is 50Kg.
6. When the vacuum dipping process is used for motor production, it is necessary to choose a thermal protector that meets the requirements of vacuum dipping.
7. When the thermal protector with bimetal activity is installed on the motor, it will generate low-frequency vibration noise under certain conditions. If the motor is used in a noise-sensitive occasion, it is necessary to confirm the use environment.
The main application fields of motor thermal protector:
1. Motors for household appliances: shaded pole motors, series excitation motors, capacitor motors (for juicers, blenders, range hoods, air conditioner motors, etc., AC motors will use temperature control, DC do not use
2. Tubular motors (for automatic curtains, projectors, rolling shutters, automatic blinds, etc.
3. Special motors (supermarket conveyor belt motors, etc.
Commonly used setting temperature of motor thermal protector: 90/100/110/125/140/150 ℃
