induction motor

[mariodileep]

Hello, If there is unstable line to ground voltage on a delta connected three phase induction motor motor what effect can it have on the motor. Given the line current and the line to line voltages are stable and within specification.
please advise.

 

[davidbeach]

If the line-ground voltage is less than the line-line voltage it probably has no affect.

 

[waross]

I second David Beach's comment.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[7anoter4]

It could be a weakened insulation somewhere-in the motor or in supply side [upstream].But I agree with the conclusion for the time beeing it is no change in motor behaviour

 

[fahad8413]

Hello all,

If the system is 3-Ph 4 Wire (i.e. Star connected, neutral grounded transformer), the voltage on any phase to ground will rise only in case one of the other two phases develops a low impedance earth leakage due to insulation failure.

In this case, there seems to be one. However, if it is well below the protection settings of the upstream switchgear (Sensitive E/F), there is no reason for immediate worry. But, it would be a good idea to get the IR's for the system rechecked.

Hope the answer is acceptable. Please correct me if I am wrong.

Fahad Shaikh.

 

[waross]

Please correct me if I am wrong.
Any fault capable of noticeably changing the voltage to ground on a grounded system will will be cleared by the protection before the voltage difference is apparent.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[7anoter4]

You are right, waross,usually the insulation degradation is so deep that the current to ground turns into short-circuit activating the protection.
But in this case-4 wires distribution- could be a current unbalance and the neutral current circulation deploys the neutral point- in a remote location
from the grounded transformer neutral.So, nothing is concerning about ,indeed.