75HP Motor Problem
75HP Motor Problem
(OP)
Hi Everyone,
I have a problem with a 75 HP motor and I hope someone could help me with that. We have installed a 75HP Gould pump in one of our car wash facilities. The model# is 66SV-6/2. Our voltage is 208V and the wiring configuration is DELTA. Our operating pressure is 275 PSI which is a normal operating pressure. The FLA for a 75 HP motor at 208V is 211A. We did measurements at various pressure and got the following results:
Line----Amperage@ No Load--------Amperage@10 psi-----------Amperage@55 psi-------------Amperage@150 psi---------------Amperage@200 psi-----------Amperage@275 psi
L1-------------40.5---------------------------99.8---------------------------127-------------------------------205--------------------------------283----------------------------314
L2--------------43----------------------------102.2---------------------------129-------------------------------205-------------------------------288----------------------------314
L3-------------41.5---------------------------99.5---------------------------127-------------------------------205--------------------------------287----------------------------314
The Line to Line voltage of the terminals @ 275 PSI is: 201V , 200V, 200V
As you see, the amperage is way too high at 275 PSI and it trips the overload every time. The manufacturer has mentioned that the Full Load Amps should be 185-Amps at 208-Volt for this Motor & at No Load, Amps should be around 50-Amps. Does anyone knows why we are getting such a high amperage? Please let me know if you need any more information and I will supply that.
Thank you all in advance.
I have a problem with a 75 HP motor and I hope someone could help me with that. We have installed a 75HP Gould pump in one of our car wash facilities. The model# is 66SV-6/2. Our voltage is 208V and the wiring configuration is DELTA. Our operating pressure is 275 PSI which is a normal operating pressure. The FLA for a 75 HP motor at 208V is 211A. We did measurements at various pressure and got the following results:
Line----Amperage@ No Load--------Amperage@10 psi-----------Amperage@55 psi-------------Amperage@150 psi---------------Amperage@200 psi-----------Amperage@275 psi
L1-------------40.5---------------------------99.8---------------------------127-------------------------------205--------------------------------283----------------------------314
L2--------------43----------------------------102.2---------------------------129-------------------------------205-------------------------------288----------------------------314
L3-------------41.5---------------------------99.5---------------------------127-------------------------------205--------------------------------287----------------------------314
The Line to Line voltage of the terminals @ 275 PSI is: 201V , 200V, 200V
As you see, the amperage is way too high at 275 PSI and it trips the overload every time. The manufacturer has mentioned that the Full Load Amps should be 185-Amps at 208-Volt for this Motor & at No Load, Amps should be around 50-Amps. Does anyone knows why we are getting such a high amperage? Please let me know if you need any more information and I will supply that.
Thank you all in advance.





RE: 75HP Motor Problem
Best to you,
Goober Dave
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RE: 75HP Motor Problem
RE: 75HP Motor Problem
A pump is a mass-flow device. That means the more material that runs thru it the more work it does. If you are pumping too much volume you are overloading the motor. You need to put in restrictions be they nozzles, smaller nozzles, orifice plates, or a flow limiting valve.
Keith Cress
kcress - http://www.flaminsystems.com
RE: 75HP Motor Problem
RE: 75HP Motor Problem
Has anything changed since the system has been running? Or is this a new installation?
Is the volume you're stating actually a measured value you have?
Keith Cress
kcress - http://www.flaminsystems.com
RE: 75HP Motor Problem
RE: 75HP Motor Problem
So you need to reduce the flow or reduce the head at which your flow is occurring at down to 250PSI.
T'wer me I would close a valve slowly while watching the ammeter until you hit nameplate. Try it briefly and see how the current responds. Some pumps won't drop current with restricted flow.
Keith Cress
kcress - http://www.flaminsystems.com
RE: 75HP Motor Problem
Keith Cress
kcress - http://www.flaminsystems.com
RE: 75HP Motor Problem
RE: 75HP Motor Problem
Keith Cress
kcress - http://www.flaminsystems.com
RE: 75HP Motor Problem
Keith Cress
kcress - http://www.flaminsystems.com
RE: 75HP Motor Problem
A motor actually intended to operate on a 208 V system will have a nameplate voltage of 200 V.
RE: 75HP Motor Problem
Throttling a valve will drop the current but it will also drop the pressure at the nozzles.
You may get some increase in performance with a higher voltage but not enough.
By the way, do you have positive pressure on the suction side of the pump?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 75HP Motor Problem
Then it is expected that current goes up as pressure (I assume dp) goes up.
338 psid * 150 gpm = 22 KW fluid power
sqrt(3)*208V&205a = 74 KW electric apparent power
A surprisingly low product of pf* EffMotor* EffPump..most likely EffPump is the problem somehow.
How is the pressure adjusted?
Do you have link to this pump curve?
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(2B)+(2B)' ?
RE: 75HP Motor Problem
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(2B)+(2B)' ?
RE: 75HP Motor Problem
It's a 3 stage centrifugal.
Pump PDF
Keith Cress
kcress - http://www.flaminsystems.com
RE: 75HP Motor Problem
I did find this with pump curve on 2nd page of pdf (page 41) which sure looks like centrifugal.
http://blumenauerpumps.com/commercialpressure/esv/...
So, going back to op, pressure is changing and currrent going up - what is being adjusted?
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(2B)+(2B)' ?
RE: 75HP Motor Problem
@dpc: The name plate just shows 230/460V. I talked to the manufacturer and they said this motor also works with 208V, but it is a very minimum voltage. When we ordered the pump, we indicated that out voltage is 208V. I don't know why they sent us a motor that they know it barely works with 208V.
@waross: Yes, I have a positive pressure on the suction side. This pump is drawing the water from a 4000 GAL tank, so I have enough static head on the suction side.
@electricpete: No, this is a multi-stage centrifugal pump. Here is the link to the curve: http://blumenauerpumps.com/commercialpressure/esv/... you should use curve 6/2. I adjust the pressure by using a globe valve downstream of the pump.
RE: 75HP Motor Problem
Here's Keith's link in a form that works: http://media.wix.com/ugd/391cd0_5b6fb3f23f1d3bead1...
RE: 75HP Motor Problem
RE: 75HP Motor Problem
I'm still confused. Is pressure reported in the op measured upstream or downstream of this globe valve?
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(2B)+(2B)' ?
RE: 75HP Motor Problem
RE: 75HP Motor Problem
Paraphrased from original post:
No load 40A
10 PSI 100A
55PSI 125A
150PSI 200A
200PSI 285A
275PSI 314A
As we go down that list from top to bottom:
valve closes more resulting in discharge pressure (upstream of valve) increasing
system flow decreases
current apparently increases.
The last item (current increases as flow decreases) does not seem consistent with the curve which shows HP/stage (I assume that is BHP/stage) increasing with flow over most of the range.
I don't know why that is. Can anyone suggest a reason for this?
I also don't understand in view of this why people are suggesting to decrease flow when your data suggests that will increase current.
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(2B)+(2B)' ?
RE: 75HP Motor Problem
I can buy that.
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(2B)+(2B)' ?
RE: 75HP Motor Problem
Because the intent of 208V systems was for smaller commercial and LIGHT industrial installations where the motor loads would be under 50HP and close (relatively) to the service entrance by virtue of it being a small facility. So motor mfrs generally don't have many off-the-shelf REAL 200V motor offerings at over 50HP, under the assumption that for the few requirements out there, the motors will likely be close to the service entrance and therefore not see much drop so the tolerance of a 230V design down to 207V will suffice, or users can special order a 200V design if not. You are in the small percentage of applications falling outside of that decision envelope on 230V off-the-shelf motors and the OEM likely did not want to wait (or pay) for a special order 75HP 200V 2 pole motor. A quick double check of Baldor's website shows that you can get 1 choice on a 200V 75HP premium efficiency motor in 4 pole, horizontal mount, but not 2 pole nor vertical, as yours is. But 230/460V vertical and 2 pole? No problem, ship it tomorrow.
An excerpt from "The Cowern Papers", an excellent treatise on motor theory from an industry expert that gives great insight into many of the design decisions that go into making motors.
"Will work for (the memory of) salami"