sump pump

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mickeyrench

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edison, n.j.
The company had a new sump motor 90 hp 3 phase 480v installed and right away the motor is drawing high current about 165amps. can it be meggered from the disconnect while it is in place? any ideas why a new motor would be running high. I have a fluke 1587 and would like to know if this can be used on motor that size. thanks for all the help
 
What's it pumping? You can certainly megger it in place, but mechanical issues like tight bearings or pumping sludge in the sump are equally suspect too.
 
mickeyrench said:
The company had a new sump motor 90 hp 3 phase 480v installed and right away the motor is drawing high current about 165amps. can it be meggered from the disconnect while it is in place? any ideas why a new motor would be running high. I have a fluke 1587 and would like to know if this can be used on motor that size. thanks for all the help
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Yes it can be meggered from the disconnect (assuming it isn't running of course). The Fluke could be used to test the insulation. Whether it can provide enough voltage for a comprehensive insulation test might be a moot point - the usual rule of thumb here (UK) is twice operating voltage plus 1000.
In any case, I would have thought that, with a new motor, insulation failure might be the result of excessive current rather than the cause.
A few suggestions:
  1. The new motor might be the wrong speed e.g. a 4-pole instead of a 6-pole.
  2. It might be connected in delta but should be wye.
  3. It could just be undersized for the duty. Is it a new application or a like for like replacement?
 
mickeyrench said:
The company had a new sump motor 90 hp 3 phase 480v installed and right away the motor is drawing high current about 165amps. can it be meggered from the disconnect while it is in place? any ideas why a new motor would be running high. I have a fluke 1587 and would like to know if this can be used on motor that size. thanks for all the help
Click to expand...

this motor is a 50 hz and controlled by a vfd , service factor is s1 and i don't know what s1 is. it pumps sewer water. I noticed the installer used 2 differrent size wires . in the vfd he used a belden cable 3370 3/0 . from the load side of cb inside vfd he used 1/0 cable to terminal bar from other side of the tb he used the 3/0 belden# 3370 and had to clip some of the cable to fit in the tb and that went to the disconnect for the pump. The 1/0 is about 2' long and the 3/0 is about 10'. There are two of these motors going to splice box and tied into a feed going back to a mcc 500amp cb. The 90 hp and a 100hp motor. There is a total of 4 pumps and i have to check and see how they are feed. I know for sure they are spliced on the same circuit together , just not sure what size cb.
 
mickeyrench said:
this motor is a 50 hz and controlled by a vfd , service factor is s1 and i don't know what s1 is.
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S1 duty means continuously maximum rated.
If the motor is 50Hz check the motor nameplate voltage. If it is a 50Hz machine it might be of UK or European origin and, if so, it is probably rated at 400V, not 480V.
Is the VSD set to give 400V at 50Hz?
 
s1- does it mean there is a service factor or is it rated at the name plate fla?
There are four motors 1@ 90hp and 3 @100 hp. They are fed from a 500 amp 480v cb . They are all soft started and i 'm not sure how many can or do run at one time. This looks like a poor design at the least with 4 pumps on 1 cb.
Does anyone know where or how i can compare the load capacity of a pump design for a 100hp motor to the same pump using 90hp? I know i asked alot of questions and i am really greatfull for all the help . There isn't a better place to increase your knowledge . Thanks
 
mickeyrench said:
s1- does it mean there is a service factor or is it rated at the name plate fla?
There are four motors 1@ 90hp and 3 @100 hp. They are fed from a 500 amp 480v cb . They are all soft started and i 'm not sure how many can or do run at one time. This looks like a poor design at the least with 4 pumps on 1 cb.
Does anyone know where or how i can compare the load capacity of a pump design for a 100hp motor to the same pump using 90hp? I know i asked alot of questions and i am really greatfull for all the help . There isn't a better place to increase your knowledge . Thanks
Click to expand...
S1 in continuous duty as opposed to the various classifications for short term intermittent and sequential duties (S2 - S8).

In post #6 you said the motor was 50Hz and controlled by a VFD and above you now say it is soft started. If it is on a Soft Start, it will run at 60Hz, 480V.
If the pump was designed to run at 50Hz speed, running it at 60Hz would increase the power by a factor of 1.73 ((60/50)^3)

That would explain the 165A you mention in post #1.
 
Just asking because we have had some softstarts that were so poorly adjusted they were the cause of many problems. If you are having an overcurrent problem after the system is up and running then I don't think the soft start has anything to do with it.
 
If the soft start was setup for a 100hp motor and then the motor is replaced with a 90hp motor does the soft start have to be setup for the 90hp, besides the overloads? thanks


i am sure it is a 50 hz
 
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