The article analyzes two faults in DC-timing-system of hoist, presents the importance of routine maintenance on measure of speed dynamo, and puts forward proposals about maintenance.
The dynamic braking means that after three-phase voltage is switched off asynchronous dynamo the dc current flows into the stator circuit to realize dynamo braking.
能耗制动是在异步电动机切离三相电源后，在定子回路通入直流电流，实现能耗制动。
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With the power being DC, the current of inner winding of the magneto is AC, and the rotating part is just similar to the magnetic rotor of synchronous dynamo.