surge testing

[FbJavier]

hello!

anyone who experience in balance impedance testing using surge comparison tester, id experience testing on 1.) DC armature winding with a rated armature voltage of 650V upon gradually applying the test voltage id notice at 250V, its wave signature distorts with tracking trace as shown on display but as i increase the the voltage over 250V it will then balance without distortion. is there something wrong in the winding? is there any test equipment that is more suitable for armature winding test? (its history has a pitch bar marking on commutator bars, no shorted nor open winding upon using growler) 2.) upon testing a 4160V (flat-wire coil) squirrel cage induction motor, id noticed a HISSING sound in the stator winding before its wave signature distorts to more chaotic trace. What makes this HISSING sound? Can anyone elaborate the occurrence of this phenomena, its posssible threat to the motor winding?

 

Thanks..

 

 

fbJavier

[marke]

I wonder if the "hissing" sound is a discharge in the winding, possibly caused by moisture. I would try drying out the winding well and repeating the test.

[electricpete]

Originally posted by FbJavier

hello!

 anyone who experience in  balance impedance testing using surge comparison tester, id experience testing on 1.) DC armature winding with a rated armature voltage of 650V upon gradually applying  the test voltage id notice at 250V, its wave signature distorts with tracking trace as shown on display but as i increase the the voltage over 250V it will then balance without distortion. is there something wrong in the winding? is there any test equipment that is more suitable for armature winding test? (its history has a pitch bar marking on commutator bars, no shorted nor open winding upon using growler) 2.) upon testing  a 4160V (flat-wire coil)  squirrel cage induction motor, id noticed a HISSING sound in the stator winding before its wave signature distorts to more chaotic trace. What makes this HISSING sound? Can anyone elaborate the occurrence of this phenomena, its posssible threat to the motor winding?

1 - This sounds to me like a thresh-hold failure. At 250 volt surge level the turn insulation is breaking over.

2 - I have seen the Baker and PJ equipment used. Often when there is exposed metal connections we hear distinct clicking around twice a second as they flashover... I think it corresponds to the repetitive surge rate. I have never heard continuous buzzing or hissing in surge test... only in ac hi-pot test. What tester do you use?