Applications of Thermal Protector in Fan Industry

Fans, as a subdivision application field of motor products, are being used more and more widely. Specific applications include ventilation of buildings and houses or outdoors, air circulation and purification of dust-free clean workshops, 5G terminal equipment and heat dissipation of wind power generation, etc. As a long-term or even 24-hour uninterrupted electrical equipment, the fan has the phenomenon of overloading work and heating and burning of the motor coil when it is locked. The installation of an overheat protector is a necessary solution. This article will specifically describe the selection and precautions for installing an overheating protector. Fans are divided into outer rotors and inner rotors due to their different structures. Due to the different power supply, they are divided into two types: DC and AC. This article focuses on AC external rotor fans.

First, the selection of the external rotor fan thermal protector

Volume requirements: Because the coil of the external rotor fan is very small and the structure is relatively compact, a miniaturized thermal protector is required at the installation position. The world’s largest fan manufacturers EBM-PAPST and ZIEHL-AGEGG select button-type products with a diameter of about 10mm and a thickness of no more than 5mm. Such products are easier to squeeze into the coil or the gap between the coil and the shell. Moreover, the button-type product shell is made of metal material, and the round shell fits tightly with the coil, so it can withstand greater coil shaping pressure. The products of SAFTTY are ST01 series.

Rated voltage and rated current: The normal thermal protector can pass the rated voltage of 250V, and the UL certification will require a voltage of 277V; in terms of current, the ST01 product of 5A can be used for low power, and the ST06 product of 10A can be used for high power. The selection standard is based on It is standard that the locked-rotor current of the fan is not greater than the rated current of the protector.

Open temperature: Generally 5-10 degrees lower than the maximum withstand temperature of the coil insulation level. For example, the E-level insulation level is the best, and the high temperature is 130 degrees. Use 120 degrees or 125 degrees thermal protectors, and the F level insulation level is the highest withstand temperature 155 degrees, you can choose 145 degrees and 150 degrees protectors.

CyclesThe normal fan lock-up time is 18 days, and the heating and cooling cycle is about 2000 times. The life of the thermal protector is generally 6000~10000 times, which can meet the requirements of the locked-rotor life; according to the different use environment, some wind power may increase High current is used for 5000 times of life test, ST01 and ST06 series can also meet this demanding requiremen.

Manual reset requirements: If some fans are in use, if they are overheated and tripped for protection, they do not need to be automatically reset to work again. You can choose to use the manual reset model of ST01+PTC. This model has a built-in PTC heating element and is disconnected in the protector contact switch circuit. After that, the circuit of the PTC heating film will be immediately connected to allow the PTC to heat up and bake the two films so that it cannot be reset automatically.

Second, precautions for use

In the use of insulating sleeves, the thermal protector must be equipped with an insulating sleeve when the shell is electrified. The head of the insulating sleeve should not be too sharp, otherwise the enameled wire will be cut and the coil will be short-circuited. The head of the ST01 series protector adopts ultrasonic welding technology to partially seal the head casing, which enhances its anti-insulation voltage performance. At the same time, the head adopts a unique process to make the head very smooth and will not cut the enameled wire. If there are more stringent requirements in actual use, the head can also be made into an epoxy encapsulation form to make the head more rounded and more convenient in the installation process. It will neither cut the enameled wire but also meet the insulation withstand voltage requirements.

Shaping pressure: ST01 and ST06 series are metal shells, which can withstand 50Kg of pressure resistance. If you need more pressure resistance, you can customize a thicker shell to solve the problem.

Some fan products have a vacuum dipping process during the manufacturing process, which has higher requirements for the sealing performance of the protector. The ST01 series adopts a unique sealing technology, which can reach the vacuum pressure of -0.08Mpa. 1%~0.3% paint rate, if in the case of -0.03Mpa, there is basically no possibility of dipping paint. However, the fluidity of the insulating varnish during actual use also has a lot to do with it, and the customer needs to provide the paint model to do the corresponding experiment to solve it. In the shipment inspection of SAFTTY, there are sampling inspections of dipping paint to prevent this problem to the utmost extent.

Many fan models have different requirements for the thickness of the protector, and the number of turns of the coil is different. If the number of winding turns is more, the volume of the coil will be larger, so that the installation space of the protector will be overstocked. The ST01 series has an ultra-thin version to meet the higher requirements of customers.                                                

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