ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
AreMetal Ladders Ever OK For Electrical Work?
by HotLine1. 01/22/18 07:31 PM
Photocell
by twh. 01/22/18 05:06 PM
VDE 0100 to introduce AFCIs
by sparky. 01/20/18 05:09 PM
MRI LED lights dimmer control replacement - wow!
by Potseal. 01/19/18 08:52 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 11 guests, and 7 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Pump Motor Overamping #66181
05/23/06 06:39 PM
05/23/06 06:39 PM
D
drillman  Offline OP
Member
Joined: Mar 2003
Posts: 97
Somewhere in Texas
Got a motor driven pump. 75 HP, 3 phase, 460 V, SF 1.15. Nameplate FLA is 87A. The pump is on a constant flow system.

Amprobed it at 96, 100, 104 amps. Voltages are within 2 volts of each other.

Is this something I should be worried about? 87 X 1.15 is 100. I am not concered with the imbalance as much as the fact that the motor is running at max all the time.

I know next to nothing about pumps so is this something I should worry about? This motor/pump combo is a backup to another pump that just failed. It has not run in about 2 years .

Many thanks

Work Gear for Electricians and the Trades
Re: Pump Motor Overamping #66182
05/24/06 01:40 AM
05/24/06 01:40 AM
S
skingusmc  Offline
Member
Joined: May 2004
Posts: 116
Simi Valley, CA USA
drillman -

You most likely want to be concerned about the imbalance, as it amounts to 4%.

The winding temps of the motor will encrease, efficiency will decrease, and life expectancy of the motor windings will decrease drastically.

Go to This Link

for a good article explaining the adverse effects of unbalanced voltage.

Steve


(edited to add link)



[This message has been edited by electure (edited 05-24-2006).]


Thanks
Steve
Re: Pump Motor Overamping #66183
05/24/06 01:00 PM
05/24/06 01:00 PM
S
skingusmc  Offline
Member
Joined: May 2004
Posts: 116
Simi Valley, CA USA
drillman -

I read your post last night and "saw" "amps" and then "thought" "voltage".

The info in my previous post does not apply, but I'll leave it in case anyone would like to get info about "voltage imbalance".

I'll email you an article about current imbalance, as I don't think it would cut-n-paste well.

While you have a 4% unbalance, it looks as if you are ok.

It is not unusual to have higher unbalance at no load than when the motor is under load. Were you reading taken under load or no load?

Steve


Thanks
Steve
Re: Pump Motor Overamping #66184
05/24/06 03:00 PM
05/24/06 03:00 PM
B
Bob  Offline
Member
Joined: Feb 2002
Posts: 182
Mobile, AL, USA
What is the voltage at the motor?

Re: Pump Motor Overamping #66185
05/24/06 10:22 PM
05/24/06 10:22 PM
J
jay8  Offline
Member
Joined: Jul 2005
Posts: 183
Vancouver, BC
The fact that this is a backup to a pump that just failed is cause for concern. It could be the pump/motor combination is undersized for the application. Has something been changed since the initial installation? If it is a centrifugal pump, you can throttle the discharge valve a notch or two to drop the current, maybe you will still have acceptable flow with the throttled valve. Either way you should take a second look at the system, compare field conditions with design values. Good luck.


Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
lil suzi
lil suzi
Midwest
Posts: 57
Joined: August 2003
Show All Member Profiles 
Top Posters(30 Days)
Admin 21
sparky 15
Potseal 15
Popular Topics(Views)
243,596 Are you busy
180,394 Re: Forum
170,865 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.018s Queries: 14 (0.005s) Memory: 0.9663 MB (Peak: 1.1034 MB) Zlib enabled. Server Time: 2018-01-23 02:21:50 UTC