Pump Starting Current

Have u looked at your motor name plate?

Have you looked in NEC art 430?

And this information is needed for what purpose?

Is there some reason why the motor data sheet is not to hand?

Is there some reason why the motor manufacturer's Technical Helpline cannot be contacted by telephone?

Is dividing the line voltage by the internal resistance of the motor such a big deal?

Is multiplying the full load current by 5 such a big deal?

if you know your RLA you can multiply that 5 times and get pretty close

Just to get thinks straight: The pump wont need any "current" but the motor driving the pump will. So the excel sheet will have to know what the motor is made off. As said just wanted to set this straight. Maybe will give you an idea of what to search next in the WWW.

Dear HP,

How to estimate the Startup torque of a pump motor - Physics Forums

There are 155,000,000 Googlle hits on this subject.

BTW, HP is for Helpless Poster, which we certainly need as a category here!!!!

It depends on the type of starter(dol/star-delta/auto tfr/vsd etc) used. Does it depend on the load(no load/part load/fully loaded etc) coupled to the motor,and why?.

I will gladly throw a life preserver to a drowning man that has fallen overboard and is struggling to stay afloat,however,when the person is in shallow water, and is screaming for help,and will not stand up and see that the water is only up to his knees, that is a different matter.

The OP has not done proper diligence in pursuing the answer on his own.He wants someone else to do the work and give him the answer.

This question is now redirected to: /dev/null.

what type of pump, ESP, flyjet, vacuum... ??? oh and just so you know... it's the motor current you need, not the pump, as previously stated!!

smaller pump motors start directly off line voltage, larger pump motors usually have some sort of soft start like star-delta....

not totally correct.... to many variations to that statement. Lets keep the answer simple, as it was a simple question

It is preferable to ask this question to the manufacturer rather than the forum members who do not have any information about the KW, voltage at the motor terminal during starting and the starting power factor ( based on the subtransient reactance).

Normally as a thumb rule starting current of a standard motor with DOL starting is about 6 times of the rated current. For energy efficient motors this will be roughly 7 times. You may please note that the starting current is inherently a motor parameter considering its rated voltage and in no way connected with the mechanical equipment to which it is coupled i.e. a pump, a conveyor or a fan. However, the duration of the starting current is dependent on the load inertia.

As you see, most here think you are not doing your work in a manner that suggests that you have the proper training/knowledge for working with electricity, they are probably right.

But I will give you an answer that you can use your whole life through:-

For any AC motor, but depending upon motor type (that you neglected to mention), starter type (that you neglected to mention) and mechanical load (that you neglected to mention), you can expect a motor to need between 5 and 8 x the normal running current.

6 x normal running current is in my experience about right and errs often slightly too high. But up to 8 is possible. You should be looking at the data sheet and the markings on the motor itself, even contacting the manufacturer - all already mentioned by others.

It should be fused with modern HRC fuses or similar (you know what these are I hope ) to allow starting, but give a good safety margin at normal loads.

Please remember the old saying when working such problems:-

"If you are unsure about something and do not want to be thought a complete idiot, keep your mouth (and/or keyboard) closed, and don't open it and remove all doubt!!!"