VFD "Endurance Test"

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charlie b

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Lockport, IL
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Retired Electrical Engineer
The electrical contractor on a project I recently inherited is questioning a specification requirement, and I can?t blame them for doing so. The spec was published by the US government. The paragraph in question is a standard boilerplate statement, and deals with the ?endurance test? of a variable frequency drive (VFD). Here is the paragraph:
Immediately upon completion of the performance verification test, the endurance test shall commence. The system shall be operated at varying rates for not less than 192 consecutive hours, at an average effectiveness level of .9998, to demonstrate proper functioning of the complete PCS. Continue the test on a day-to-day basis until performance standard is met. During the endurance test, the contractor shall not be allowed in the building. The system shall respond as designed.
My questions:

  1. Has anyone had to perform this ?endurance test??
  2. Can anyone tell me why the contractor must be kept out of the building during the test?
  3. Can anyone tell me what ?PCS? means?
  4. Can anyone shed any light on this testing process?

 

jim dungar

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Wisconsin
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PE (Retired) - Power Systems
Maybe:

PCS = Process Control System = VFD + Driven Load + controller

They don't want the contractor doing any 'tweaking' during the test.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
The electrical contractor on a project I recently inherited is questioning a specification requirement, and I can?t blame them for doing so. The spec was published by the US government. The paragraph in question is a standard boilerplate statement, and deals with the ?endurance test? of a variable frequency drive (VFD). Here is the paragraph:

My questions:

  1. Has anyone had to perform this ?endurance test??
  2. Can anyone tell me why the contractor must be kept out of the building during the test?
  3. Can anyone tell me what ?PCS? means?
  4. Can anyone shed any light on this testing process?


It does not sound all that far off from tests equipment I have been involved with has had to endure. It is not unusual for a supplier to be required to run a system without any intervention for a specified period of time and meet specific requirements.

I have never had a situation where we were kicked out of the room but it does not sound like an unreasonable thing. The machine has to run unattended for the next 20 years. If it cannot do 192 hours unattended who is fooling who?
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Maybe:

PCS = Process Control System = VFD + Driven Load + controller

They don't want the contractor doing any 'tweaking' during the test.
I've seen that spec before, the PCS meant Pump Control System on mine. The spec was part of the Division 11 Equipment spec, where it called for the pumps, motors and VFDs to be packaged together and supplied as a complete system with guaranteed performance. This is typically done by the pump packager, often the pump manufacturer or their agent. The purpose is to say, SOMEONE must take overall responsibility for performance of the entire system, no finger pointing, no shucking and jiving with the pump mfr saying the VFD is not performing right, then the VFD mfr saying the motor is wrong, and the motor mfr saying the pump mfr picked the wrong motor, etc. etc. etc. But because it is the VFD that makes it all work, the performance testing portion is often put into the VFD spec.
 
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