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Participant

Join Date: Jan 2011
Posts: 4

DC Supply Appears in Motors. What is Impact?

11/21/2015 4:32 AM

We face 2 numbers of 11kv motors burn-(10 yr old motors) after the Hi pot test , but vendor reported to us while hi pot cable removed , then how motor is burn whils starting....i am the clint my side doubt if Hi pot test voltage appear to the motor winding what will happen ...Applied voltage is 11kv...

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Guru

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#1

Re: DC Supply Appears in Motors. What is Impact?

11/21/2015 3:49 PM

Simple. Your over current protection arrangements are inadequate, and you need to hire someone who knows more about this topic than you do.

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Power-User

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#2

Re: DC Supply Appears in Motors. What is Impact?

11/21/2015 11:34 PM

Hello, . . . your English is ATROCIOUS!

How san anyone understand what you have written? - other then "two motes have burned".

Incidentally, . . . only an insane person would do a HiPot Test (Vtest= (2 x V +1)kV). on a 10 year old motor. You have likely damaged the insulation.

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#4
In reply to #2

Re: DC Supply Appears in Motors. What is Impact?

11/22/2015 3:36 AM

GA

My take is also that the insulation was damaged by the test....

An insulation test BEFORE the Hi-Pot test, may have allowed some extra cleaning, extra work on getting the insulation to a far better level (its not my area of expertise), before Hi-Potting...

Maybe an insulation test, AFTER the Hi-Pot test MIGHT have shown the "new" problems, before the motor was run.....and thereby "terminated"!!

Just a thought!

I found this on Wiki, which appears to my untrained eye to be really accurate, especially the underlined part!!:-

A Hipot test (also called Dielectric Withstanding Voltage (DWV) test) verifies that the insulation of a product or component is sufficient to protect the operator from electrical shock. In a typical hipot test, high voltage is applied between a product's current-carrying conductors and its metallic shielding. The resulting current that flows through the insulation, known as leakage current, is monitored by the hipot tester. The theory behind the test is that if a deliberate over-application of test voltage does not cause the insulation to break down, the product will be safe to use under normal operating conditions-hence the name, Dielectric Withstanding Voltage test.

In addition to over-stressing the insulation, the test can also be performed to detect material and workmanship defects, most importantly small gap spacings between current-carrying conductors and earth ground. When a product is operated under normal conditions, environmental factors such as humidity, dirt, vibration, shock and contaminants can close these small gaps and allow current to flow. This condition can create a shock hazard if the defects are not corrected at the factory. No other test can uncover this type of defect as well as the Dielectric Withstand test.

From here:-

Hi-pot Testing

This makes me believe that the company you used for doing the Hi-Pot test does not have any idea on correct procedures with regard to insulation and Hi-Pot testing.

Find another company to do this work.

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#3

Re: DC Supply Appears in Motors. What is Impact?

11/21/2015 11:45 PM

I suggest that you immediately notify management of your inability to perform your duties.

After all, your company's Business Ethics states:

"We encourage our employees, contractors, vendors, consultants, shareholders and other stakeholders to communicate directly and honestly about compliance issues or any other ethical concerns."

Remember, HE is watching you

Do you want to disappoint HIM?

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Participant

Join Date: Jan 2011
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#5
In reply to #3

Re: DC Supply Appears in Motors. What is Impact?

11/22/2015 1:52 PM

you misunderstood, with un wanted replay from you , actually I am not involved this job purely this vendor job only ..just I want clear my doubt only, before replay just read the content then replay....ok,,, don't do un wanted replay to others in next time

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#6
In reply to #5

Re: DC Supply Appears in Motors. What is Impact?

11/22/2015 2:39 PM

I understand that you know nothing about electric motors, but are trying to convince others that you do.

Getting information from an anonymous forum on the internet and then representing it as your technical expertise is untruthful.

And lest we forget, you came to the forum to ask the question.

You don't get to make the rules.

Just ignore the answers you don't like.

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#7

Re: DC Supply Appears in Motors. What is Impact?

11/23/2015 10:50 AM

The 2E + 1,000V Hy-Pot test is an acceptance test that should only be executed one time during the life cycle of a piece of equipment.

This type of test should only be done when the equipment is new and only after it has been installed at the site.

After the initial acceptance test has been completed the applied Hy-Pot voltage level on any test performed in the future should not ever exceed the equipment nameplate rating.

When testing with a Hy-Pot unit the test voltage should be applied in incremental steps over a standard insulation test time interval. (Review test set directions.)

Used equipment should not ever be subjected to acceptance test voltage levels and should never be subjected to any sudden high voltage impulse testing as severe insulation damage will occur.

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