Three-phase asynchronous motor winding grounding

1,fault phenomenon:chassis charged,heat control circuit is out of control,winding short circuit,the

normal operation of the motor.2,the reason:the winding be affected with damp be affected with damp

single phase asynchronous motor decreased insulation resistance;Motor overload for a long time;The harmful gas corrosion;Metal foreign body into winding internal damage insulation;Rewind stator winding insulation damage when touch the core;Winding end touch end cover frame;Set,rotor friction caused insulation burns;Lead wire insulation damage into the shell;Overvoltage (such as lightning) insulation breakdown.3.Check the method:(1) the method of observation.Through visual winding overhang and line slot insulation observed with and without damage and charred traces,is the pick up location.(2) the multimeter test.The multimeter low-resistance archives check,reading is very small,it is grounded.(3) megohmmeter.Selected according to different levels of different measuring each group resistance of insulation resistance by megger generator stator are,if the reading is zero,then the winding grounding,but the motor insulation be affected with damp be affected with damp or breakdown due to accident,must determine on the basis of experience,generally pointer swing timing in "0" place,its have certain resistance value can be thought of.(4) try to light.If try lights,winding grounding,if found somewhere with a spark or smoke,is the place for winding grounding fault point.If lights dim the insulated grounding breakdown.

If the light is not bright,but also showed a spark when the test stick electric motors 12 volt ground,winding yet breakdown,just seriously be affected with damp be affected with damp.Also can use hardwood on the edge of the shell of the seam allowance tapping,to a certain place when a out a bright,when electrical current when broken,it is ground.(5) current wear burning method.With a regulating transformer,after the power is connected,ground quickly heating and insulation smoke is

the pick up location.Should pay special attention to small motor shall not be more than twice the

rated current,no more than half a minute;Big motor as 20% - 20% of rated current or increasing current,burning to the ground just immediately without electricity.(6) packet elimination method.For the pick up location in iron core and burning more severe,in my heart burning loss of copper and iron www.facebook.com/dongfeng.motor core melt together.Approach is to put the grounding of one phase winding is divided into two and a half,and so on,finally find out the ground.In addition,there are high voltage testing method,magnetic exploration method,power frequency vibration method,etc.,differ a introduced here.4.Methods:(1) the winding drying should be affected with damp be affected with damp cause ground,when cooled to about 60-70 ℃,pour insulating paint again after drying.(2) the end winding insulation damage,in receiving is located in the back of the insulation and painting,dry again.(3) windings to place in the groove,should rewind or replace part windings components.Finally apply different measured by megger,meet the technical requirements.