HM2-100L1-4-2.2KW three phase asynchronous motor for star connection. After starting 2 hours after normal output operation, still with full load, the motor speed is decreased rapidly, the winding heats up quickly, if you want to maintain the original speed operation, with only 60% of the rated load, once the motor stops will not re-start.
Failure Analysis: the above phenomenon, multi-phase asynchronous motor "walking single-phase. When a power failure, the star connection of the two-phase winding turns in series, each phase winding 1/3 rated power into the original share share 1/2 rated power per phase winding load increased by 1.5 times, phase winding current is also increased by 1.5 times due to the load. At this point, each phase winding voltage is only 190V, reduced to 109/220 = 1/1.16 times. If the load is constant, the electromagnetic torque generated by the motor is also unchanged, the rotor induced current I2 must be a corresponding increase of 1.16 times, in order to keep the torque and the same as the original, so that the rotor induced current response to the stator side, per phase stator winding current total increase of 1.5 * 1.16 = 1.73 times the load current is much greater than in the past, but smaller than the short-circuit current, a range of over-load and short-circuit between a failure.
Three-phase asynchronous motors "walk single-phase, single-phase current can not produce a rotating magnetic field, the motor can not produce starting torque, the motor starting up. Visible, three-phase asynchronous motors "walk single-phase, still at full load (rated power), the motor speed decreases, the winding heats up quickly, over time, the windings will be burned.
Repair methods: For the motor running, if the sound is suddenly not normal, speed was low, should immediately stop inspection. Ammeter Measuring current when the motor has shut down prior to the three-phase current balance, the absence of such a device, re-closing after the shutdown, motor buzzing does not start up, mostly due to a phase fuse blown cause , wind up, no spark on the knife-edge of the phase. In this case, replace the fuse can be.
