The electric valve is the automatic control device of the sluice switch, which is widely used in homes, factories, institutions, units, schools, etc. It is very convenient for remote scheduling and intelligent control of water resources.
Mainly by the control circuit and small motors, valves and other components. The switch of the valve is completed by the rotation of the small motor, and the rotation of the small motor is completed by the control circuit. The control circuit converts the remote command into the switch control signal in time, and controls the small motor to drive the electric valve to complete the switch action.
The switching process of the electric valve is mechanically driven. In this set of transmission system, small motors are prone to overload or gamble due to lack of lubricant, bearing wear, rust, dust and other issues, from burning the motor to burning the motor and wires. It even caused a fire accident.
Therefore, the motor must be designed with overload protection and gambling protection circuits to ensure safe operation. The traditional design uses bimetal thermostats to protect the motor from excessive temperature. Since the motor is overloaded or gambled, the current is very high, causing the temperature to rise rapidly. The bimetal thermostat disconnects the circuit when it senses high temperatures.
However, the bimetal thermostat does not remain disconnected after the circuit is opened. After the circuit is disconnected, there is no current. The motor temperature gradually decreases. The thermostat will turn on the gambling motor again, and the motor will continue to generate heat when the temperature is controlled. The device is again protected, so that the cycle acts. If the user runs the motor suddenly when the motor clears a foreign object after a gamble or checks, an accident such as personal injury may occur.
Bimetal thermostat is only for temperature, not for the current, the motor repeatedly after the high current gambling, but also burn out its control circuit, and now there are aluminum or copper clad aluminum wire wound motor, such a motor temperature The rise is faster and the thermostat may not have been disconnected.
The coil of the motor has been burned out. For this reason, we recommend that PolySwitch (positive temperature coefficient) be used for overload protection and stall protection of the motor. There will be no repetitive start-up of the motor and consequences or disasters will occur because the PolySwitch PPTC device can At the same time, over-current protection and over-temperature protection are completed, and this protection state is maintained until the power is turned off before returning to the initial state.
The specific application is shown in the figure below.
Application of PolySwitch PPTC in Typical Protection of Motorized Valve Motors
The use of PolySwitch PPTC devices for motor stall protection and overtemperature protection is a cost-effective protection scheme. PolySwitch PPTCs suffer from high currents and high temperatures in the event of short-circuit, over-current, over-temperature, motor stall, and other fault conditions. Under double action, it can quickly change from low resistance state to high resistance state than bimetal temperature controller, which can limit motor current in time and protect motor and control equipment.
And always maintain this state of protection, only after power off PolySwitch PPTC devices will return from a high-impedance state to a low-impedance state. Uninterrupted PolySwitch PPTC will not recover, which can effectively avoid the possible and potential problems and hidden dangers of the above electric valve motor.
This article was edited by Qin Jin Electronics, official website fuse-tech.com
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