What are the key quality points for hydraulic testing of explosion-proof motors?

The components that make up the motor casing must undergo a hydrostatic test after precision machining, and the test result must be maintained for 1 minute. The test result is considered qualified if there is discontinuous dripping (1 drop of water every 10 seconds is considered discontinuous dripping). When no reference pressure measurement is conducted, the test pressure is 1 MPa for Class I, IIA, and IIB motors; The pressure of the IIC motor is 1.5MPa. When conducting a hydrostatic test, the following points should be noted: When conducting a hydrostatic test, the components should be handled with care and the explosion-proof surface should be protected to prevent collision. After the hydrostatic test, the internal water and foreign objects of the components must be cleaned to prevent rusting. After the components are dried, the mating surfaces and threaded surfaces of the bolts and screw holes must be coated with anti rust oil before assembly. The water pressure test site must have protective measures to prevent the casting from shattering or injuring people during the test. During the storage and stacking process of components, hard cardboard or thin rubber sheets must be placed between layers to prevent collision.

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What is the working principle of a three-phase asynchronous motor?

(1) Generation of rotor induced current When the stator winding of an electric motor is supplied with three-phase symmetrical alternating current, a rotating magnetic field rotating at a speed of ns is generated between the stator and rotor. Since the rotor is initially stationary, the rotor conductor will be cut by the rotating magnetic field. According to the principle of relative motion, we can also consider the magnetic field as stationary, while the rotor conductor rotates relative to the magnetic field, cutting the magnetic field lines and generating induced electromotive force. As the two ends of the rotor conductor have been short circuited by a short-circuit ring, the conductor has formed a closed circuit, so induced current is also generated in the rotor conductor. (2) Generation of rotor electromagnetic torque The rotor conductor that generates induced current is called an electrified conductor. The electrified conductor is subjected to electromagnetic force in a magnetic field, generating electromagnetic torque to drive the rotor to rotate. Moreover, we can also determine the direction of rotation of the rotor conductor based on the left-hand rule, which is the same as the direction of the rotating magnetic field, but operates at a speed slightly lower than the rotational speed of the rotating magnetic field. Due to the fact that the speed n of this type of motor is always lower than the speed ns of the rotating magnetic field, it is called an asynchronous motor. Also, because the rotor current of this type of motor is generated by electromagnetic induction, it is also called an induction motor.

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What causes the motor winding to ground?

(1) Asynchronous motors are overloaded for a long time, causing friction between the stator and rotor (sweeping the bore). (2) The insulation of the winding is affected by moisture, which reduces the insulation performance and leads to grounding (commonly known as "shell collision") faults. (3) When replacing the stator winding, the insulation slot is not properly padded or damaged. (4) The winding end is too long and collides with the end cover

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