# Per Unit Calculations help

1. Jun 5, 2012

### DireStraits1

1) I'm not sure how to solve this question

A 20MVA induction motor connected at 13.8kV draws a load current of 1.0 p.u, 0.85 power factor lag. Calculate the rated load current in Amps and the real power and reactive power drawn by the motor. Express these quantities in per unit form using the apparent power of the motor as the VA base, and the motor rated voltage as base voltage.

2. Jun 5, 2012

### DireStraits1

I know i'm not supposed to post homework questions but my profesor told me like literally three different variations of apparent power formulas and at this point really I dont even know what formulas to use

3. Jun 6, 2012

### davenn

There is a homework section where this should have been posted
along with a set of guidelines on how to set out your query

i suggest you repost in there using the format that is given and
that may engender some help for you :)

BTW welcome to PF :)

Dave

4. Jun 6, 2012

### Studiot

Doubtless a mod will eventually move this to homework.

Meanwhile the first question is do you understand the per unit method and terminology?

In particular what do you think 1.0 pu means?

5. Jun 6, 2012

### jegues

A good starting point would be to select base values for the power and voltage.

Once you have the rated values of power and voltage in per unit form finding the rated load current shouldn't be to difficult.

6. Jun 6, 2012

### Staff: Mentor

Can you solve it when worded like this:

A 20MVA induction motor connected at 13.8kV draws full rated load current at 0.85 power factor lag. Calculate the rated load current in Amps and the real power and reactive power drawn by the motor.