Winding is an important part of motor, moisture, heat, corrosion, invasion, the impact of external forces can cause damage to the windings.Electrical overload, under-voltage, over-voltage, lack of running also can cause winding failure. Generally wingding fault have winding ground fault, short circuit, open circuit, wiring error. Now introduce failure phenomenon, the causes and inspection methods respectively.

    one．Winding Grounding

    Means grounding between winding and iron core or frame caused by insulation damage。

    1.Fault phenomenon

Frame charged case, the control line out of control, short-circuit winding heating, lead motors can not operate normaly.

    2.Cause

Winding insulation resistance cause of damp ; long-term overload;rusty by harmful gases; winding insulation damage cause of  metal junk; winding insulation damage when winding; winding insulation damage cause of winding end tuching the frame or rhe cap; winding insulation damage cause of the friction between stator and rotor;wiring friction cause of the tuch of the frame; over-voltage (eg lightning) damage the insulation.

    3.Examination

    (1)Observation Winding through the visual and the trough in the end of insulation and charred observe any signs of injury, if it is ,the location is just the point.

    (2)Multimeter Test Low profile to check with a multimeter, the reading is very small, it is grounding.

    (3)Megohm table. Selected according to different levels and different forms ,measure megohm insulation resistance of each resistor, if the reading is zero, then the winding grounding, but damp or electrical insulation breakdown due to accident, to be determined based on experience, generally speaking pointer in the "0" swing, department from time to time, that it has a certain degree of resistance

    (4)Test lamp method.If the test lights on, winding grounded.If accompanied by sparks or smoke somewhere, then the ground is for the winding point of failure. If the light micro-light ,there is grounding insulation breakdown. If the light does not shine, but testing grounding rods also spark, that is not yet been winding breakdown, but a serious damp. Hardwood can also be used to knock the edge of the frame, when a light sparking,that means the current pass off, then there is the grounding point.

   (5) Current law to wear burn：Regulator with a transformer, connect the power , the grounding point will get heat soon, the grounding point is where smoke take place. Should pay particular attention to that the small motor is no more than twice of the rated current, time is no more than half a minute ;big motor rated current is for 20% -50% of the rated current or gradually increase the current, to take place just as soon as it smoke.

   (6) Packet out methods.Where the grounding point happens,it burnt in the core, burning of copper wire together with the core melt. The method is to separate one phase of grounding winding, and so on, then find out the location of the final.

In addition, there are high-pressure test, explore the needle method, such as frequency vibration method, we couldn’t introduce one by one here.

    4.Approach

   (1)Winding ground caused by damp should to dry first, when cooled to 60 - 70 ℃, pour the insulated paint, and then dry.

   (2)End-winding insulation damage ,at the ground point to deal with re-insulation, painting, and then dry.

   (3)Winding at the tank, then rewinding or replacement the part of winding.

　 Finally, measure with megohm to make sure it to meet the technical requirements.