how to calculate induction motor rating (HP) if name plate is missing from mot

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how to calculate induction motor rating (HP) if name plate
is missing from motor at site condition ?

Question Posted / babula

6 Answers
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how to calculate induction motor rating (HP) if name plate is missing from motor at site condition..

Answer / senthil kumar.i

while name plate is missing,

first we are taken the details from the motor bellow
1. torque
2. Motor Rpm.

sutitute the given formula.

BHP = 2*3.14*T.N / 60 * 746

where T is torque and N is motor Rpm.
torque unit is nm.
we can get the Missed name plate motor HP.

Is This Answer Correct ?

46 Yes

28 No

how to calculate induction motor rating (HP) if name plate is missing from motor at site condition..

Answer / manoj

1. Switch on the motor & measure the current (i) using Clamp
meter.
2. The calculated current (i) should be multiplied with
250Watts.
3. The result value should be divided by 230Volts i.e the
present voltage ratings.
4. The result of the step 3 will be the induced motor
ratings in HP.

This is illustrated with a small example below:
Assume that a motor of 5HP 3-phase is not having a name plate.

For 5HP motor, the current ratings will be around 7amps.
As we all know that, 1amps=250Watts.
So, multiply 7amps with 250Watts i.e 7x250=1750
The result answer 1750is divided by present input voltage
i.e 230V.
1750/230=7.6
Hence the result answer is the induction motor's rating in HP.

Another easy method to calculate this is:
check the current & divide it with 1.39(current rating of 1
HP motor)
the result answer will be the motor rating in HP

Is This Answer Correct ?

26 Yes

16 No

how to calculate induction motor rating (HP) if name plate is missing from motor at site condition..

Answer / seshasai bagadi

APPLY 440 VOLTS AT NO LOAD TO THAT MOTOR AND FIND THAT NO
LOAD CURRENT BY CLAMP METER.,
AS INDUCTION MOTOR TAKES 30 % OF FULL LOAD CURRENT AT
NOLOAD .,HENCE RATING CAN FIND BY USING..
P=(1.732)(V)(I)
WHERE V-RATED VOLTAGE(440V)
I-FULL LOAD CURRENT (CALCULATED)
P-RATING OF MOTOR IN KW
ASSUME UNITY POWER FACTOR

Is This Answer Correct ?

20 Yes

12 No

how to calculate induction motor rating (HP) if name plate is missing from motor at site condition..

Answer / puja

HP = 2*3.14*t*n/60*746

Is This Answer Correct ?

8 Yes

7 No

how to calculate induction motor rating (HP) if name plate is missing from motor at site condition..

Answer / sajid khan

check the current by clamp meter on no load condition.
multiply this no load current to 2.5-3, and hence you will find your final answer.

Is This Answer Correct ?

1 Yes

3 No

how to calculate induction motor rating (HP) if name plate is missing from motor at site condition..

Answer / ramendra shukla

As we know the Relationship of Mech. HP with Elect. KW is-
HP = 0.734 KW
P= VI in KW (let PF is unity or pure resitive load)
First we will get the the Voltage V, and then the current,
C in amps By this we will calculate the Horse power ,HP.

Lets have an example
Q:- A motor is taking the current as 30 amps & the voltage
is having 420 calculate how much HP it have??
ANS :
We know HP =0.734 KW

& P= VI cos@ (let cos @=1 or pure resitive load)
then
P = 30x420x1 KW
= 126 KW
So,
HP =0.734x126 :=92 HP