Product Description
Thermal relay is a kind of protective electric appliance, mainly used for overload protection of asynchronous motor. Its role is to use the thermal effect principle of the current to cut off the motor circuit when there is an overload that the motor cannot withstand and provide overload protection for the motor.
Glass cleaning machine accessories Thermal relay is used to protect the glass cleaning machine motor and other important components, the following is a detailed introduction:
How it works
Current thermal effect: thermal relay is mainly composed of thermal elements, bimetallic pieces, contacts and so on. The thermal element is usually made of copper or constantan. When the motor of the glass cleaning machine is in normal operation, the current passing through the thermal element is the rated current of the motor, and the heat generated by the thermal element makes the bimetallic sheet in normal condition. If the motor is overloaded, the current increases, and the heat of the hot element increases.
Bimetallic sheet deformation: Bimetallic sheet is composed of two metal sheets with different expansion coefficients. The heat transfer of the heat element to the bimetallic sheet increases its temperature, and the bimetallic sheet will bend and deform due to the different expansion coefficients of different metals.
Contact action: When the bimetallic sheet bends and deforms to a certain extent, it will push the contact action. Contacts are divided into normally open contacts and normally closed contacts. Generally, normally closed contacts are connected in series in the control circuit of the motor of the glass cleaning machine. This often closed contact is disconnected, and the motor control circuit is cut off, so that the motor stops running and overload protection is realized.
Effect of action
Overload protection: prevent windings overheating, insulation aging or even burning due to long-term overload operation of the glass cleaning machine motor, and ensure the safe operation of the motor within the rated load range.
Phase break protection: when a phase break fault occurs in the motor of the glass cleaning machine, the cooling displacement of the compensating bimetallic sheet connected in series with the phase, and the bimetallic sheet without phase break produce differential effect, so that the thermal relay accelerates the action, cuts off the circuit, and protects the motor.
Phase sequence protection: it can monitor the phase sequence of the three-phase power supply. If the phase sequence is wrong, the thermal relay will cut off the circuit to avoid the inversion or abnormal operation of the motor due to the phase sequence error, and protect the mechanical parts of the motor and the glass cleaning machine.
Common faults and causes
No action: thermal relay and motor do not match, rated technical value is too large; External wiring screw virtual connection, virtual welding; The setting value of operation current is too large; Burning or desoldering of thermal elements; Mechanical action mechanism wear, stuck; Guide plate out, etc.
Misaction: the setting value is too small; Motor drag time is too long; High operating frequency; Strong external shock vibration; Bimetallic sheet - thermal element relay is not suitable for reversible operation, reverse braking or sealing on and off; The installation does not conform to the regulations or the surrounding temperature is too different from the temperature of the protected equipment.
The action is unstable, slow and fast: the internal mechanism of the thermal relay individual parts loose; The current fluctuates too much.
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