# How calculate ampere for electric motor?

Generally for electric motor size,it rated by horsepower (hp) or kilowatts (kW) unit.We can recognize the electric motor size when refer to their kilowatts or horsepower.So from power (kW/hp), how we can know the full load ampere for electric motor?

This time i want share about how to calculated the full load ampere (FLA) of electric motor from their power rated.It not difficult if we know the right formula to get the answer.From this calculation we only can estimate the value of full load ampere.

We cannot get the actual full load ampere because it depend on efficiency of motor.If electric motors have a higher efficiency rating,it will draw fewer amps, for example a 10 HP motor with a 60% efficiency rating will draw about 65 amps at 230 VAC compared to about 45 amps for a motor with a 80% rating.

## How to calculate from power ( kW & HP ) to ampere ( I )?

### 1) Kilo watt (kW) to ampere ( I )

For 3 phase power supply ; kW = I x V x 1.732 x pf

For 1 phase power supply ; kW = I x V  x pf

Example : 1 unit compressor size rated 37 kw,415 VAC,3 phase and 80% pf,calculate the full load ampere?

Calculation :

kW = I x V x 1.732 x pf

I = kW / (V x 1.732 x pf )

I = 37 / (415 x 1.732 x 0.8 )

I = (37 / 575) x 1000

I = 64.4 ampere ( full load ampere)

### 2) Horse power ( hp ) to ampere ( I )

First we must convert from hp to kW using this formula :

1 Hp = 0.746 kW

After that use the formula kW to ampere :

For 3 phase power supply ; kW = I x V x 1.732 x pf

For 1 phase power supply ; kW = I x V x pf

Example :-

1 unit induction motor power rated 25 hp,200 VAC,3 phase,90 % power factor,calculated the full load ampere.

Calculation :-

kW = 25 hp x 0.746

kW = 18.65

kW = I x V x 1.732 x pf

I = kW / V x 1.732 x pf

I = 18.65 / ( 200 x 1.732 x 0.9 )

I = (18.65 / 311.76) x 1000

I = 59.8 ampere ( full load ampere )

1. Sinnadurai Sripadmanaban says

Should we take into consideration the efficiency of the motor?.

• lemau says

For efficiency is not compulsory if we don’t have the value.,we can ignore the value :D

• Steve says

Can you tell me what amperage draw would be for a 1.1 hp motor running on 24 volts

• hasan says

If it’s single phase then
p=vi.pf.
1.1×746=24ix1
i=34.2amp
If its three phase then
p=1.732vixpf here pf=.8
i=24.67amp.

• EMMANUEL says

What is the current draw for a 3phase 415V 60HP electric motor?

• ANuj says

three phase then
p=1.7328VIxpf here pf=.8
I=P*.746/(1.732*415*.8)*1000=77.84Amps

• Robert Karkafi says

What is the 3 Phase AC Current draw for an 80A DC Motor running at 440VDC?
Thank you
Robert Karkafi
Engineered Drive Systems
Los Angeles, Ca

2. Steve Sedgwick says

In your formula Efficiency factor is not accounted – is there some reason for this. I thought the formula was kW = I x V x 1.732 x pf x Efficiency?

• lemau says

Yes Steve..it true.You can include with efficiency value if you know but if not you can skip it.

• manno says

What is 1..732

• Lemau says

Square root 3 = 1.732

• M.NARESH says

√3 = 1.732

3. amir says

amir.masror@gmail.com

4. Ronald says

Hi! Is the power factor required also? or If I didn’t know the p.f. can I use 0.8? Our motor specs are 18.5KW, 460V, 3PH.

• Lemau says

Hi,Normally i just put PF to 1 but it’s ok to put PF 0.8

5. Akash rajhuns says

hiii

you can also use

KW = √3 × V× I × cos¢

cos¢ = 0.8

• Lemau says

Yes Akash,Thanks for sharing the formula

6. dheeraj says

a motors rating 10kw !!!!! what its means this motor will consume 10 kw per sec ??? or 10 kw per hr?????

7. jacob says

8. HARI KRISHNA SINGH says

how can i found 3 ph motor efficiency

9. Joshy.G.S says

You should say P = √3VIcos¢
Watt is the unit of power, to convert Watt to kilo watt divide by 1000

10. chinna says

a 48v dc motor with nominal power 11kw. how can i calculate pf

11. NIRMAL MEHTA says

WHAT IS THE FORMULA AS UNDER:
440 V, 60 H.P., 55 AMPS, PF .95 & 12 HOURS
NOW WE WANT HOW MUCH UNITS WILL CONSUMPTION AS ABOVE POINTS.

• tukaram haldankar goa says

60 multiply by 0.746 as converting ratio you will get watts per hour and multiple for 12 hour is 44.760 kilowatts per hour multiple for 12 hour is 537.12 for 12 hour, calculate this kw multiple ain unit charges by electricity per unit you will get your bill……

12. M.NARESH says

1 HP = .746 KW
GIVEN DATA IS 20 HP AND WE NEED TO FIND THE AMPS RATING

20 HP = 20 * 0.746
= 14.92 KW
HERE 14.92 KW , IT IS 3-PHASE ( ABOVE 4 KW WE CONSIDER 3-PHASE AS PER NEC )

P = √3 V I cos¢
P = 14.92 KW
V = 415 V
cos¢ = 0.8
√3 = 1.732
I = ????

P = √3 V I cos¢
I = ( P / √3 V cos¢ )
I = (( 14.92*1000 ) / ( 1.732 * 415 * 0.8 ))
I = 25.94 A
I = 26 A

• bac +84919261294 says

yes

13. M.NARESH says

KW/KVA

14. john says

I made a blower. The fan is OD 33.5″
6″thickness and 55 kg Wight
Which power motor required (HP)

15. john says

I made a blower. The fan is OD 33.5″
6″thickness and 55 kg Wight
Which power motor required (HP)
2800 rpm

16. tushar says

hiee, for 3 phase 1kw ac motor how much the maximum current rating is acceptable?

17. Littu chirayil says

How to calculate amper when horsepower is given for 3 phase ?

18. himanshu says

A 20 H.P, 3 Phase supply ,50Hz , 440 Volt in induction motor .find out full load current?

19. Tushar says

we are having 3-phase BLDC hub motor (800W ,48V).
we have to run this motor for 2 hours with Lithium-ion battery.
Then how to decide the battery capacity?

20. Narsing says

how to find pf

• rupesh says

kw/kva

21. anil says

Is motor rpm is necessary to calcultae full load current?

• binod jaipuria says

Short trick kw to full load ampere

• John Lemau says

Not necessary. Full RPM = Full load ampere

22. MEshari says

how to Calculate the actual running current of a motor such as: moter name plate:
P=75KW
V=440
Pf=.89
phase=3
incoming V=480V using softstarter

23. sushil says

which type (watt) inverter require for run 1 hp electric motor.

• sushil says

i phase 230 volt motor

24. Rami says

Hi Gents
I have a pump with Diesel engine 1450 RPM, 160 KW, Soi wants to change the diesel engine by Electrical Motor 1450 RPM, 160 KW, 3 Ph, 380 Volts, 50 Hz, so I need to know how many Amp. I need for each one phase ( they write in the motor 280 Amp is this total for all 3 ph or 280 Amp for each one phase ) Cheers….

25. Viren says

Hi, if I’m having 15 kW motor , 3phase, pf .8 star-delta starter. How can I find How much current will flow in star condition & how much in Delta?! Pls answer. Thank you

26. Pavan Rajure says

Starting current of 10 HP induction Motor is_________ times full load current
A)5
B)8
C)10
D)20

• John Lemau says

It depend what motor starter that you use..

DOL –> 5- 6 X FLA
AUTO TRANS –> 3-4 X FLA
STAR DELTA –> 3-4 X FLA

The best is VFD – Variable Frequency Drive

27. Vikash says

We have motor rating in KW, it means KW power take in how much time

• Vikash says

Time in sec. Or hour

28. karthi says

what is the current rating of 200hp motor?

• John Lemau says

Full load amp for 200hp approximate = 275 AMP

• Anshu Singh says

Approx 245Amp

29. Jitendra Lohar says

1. How to calculate stating current of single phase and three phase motor ?
2. How to decide or calculate start capacitor or running capacitor for single phase motor ?

30. inayat Hussain says

A motor follows the operation as
20kW 120 sec
10kW 120 sec
Stopped 280 sec

What will be the continuous rating of motor for above operation.

31. Ashish Patidar says

I have 2 same motor (equal power, rating and brand) 3 Phase, running on same type of job on two different machines, one of them is drawing 45 amps where as other is drawing 50 amps of current. They run 24*7 in plant so i want know is how much unit each one consuming ??

32. NIRMAL says

WHAT IS FULL LOAD CURRENT FOR 30 HP 3 PHSAE MOTOR?

33. art says

Good way of explaining, and pleasant post to take facts regarding my presentation subject matter,
which i am going to convey in college.

34. ajeesh says

when 3 phase supply input it will be rectified ,so the rectified dc power 10kw ,then it will be through on filter so how i can choose the capacitor value and i want proper calculation
in the circuit dc voltage?
current?
filter capacitor value?
capacitor ripple peak current and peak voltage?

35. Murugavel says

0.37 kw motor Thermal overload setted 1.1 amps
400v 3ph ac 50 hz

motor data
pls explain anybody
what concept on this

36. Vimal says

What will be the motor load in 3 phase 40 hpmotor runs ons 960 rpm ??

37. Senthura moorthy.A says

what is the full load amp in given details below..?
1hp motor ,240v rating ?
Please share the ans and detail calculation with pf ?

38. Suraj says

What could the maximum current and rated current for a motor with following specs:-
3 phase
415 V
11 kW

39. Prahlad Choudhary says

Sir normally 25hp 3phase motor 440volt. Per kitne amp’s current khapt karta h

40. Fadhili Issa says

Hello. Am a big fan of your precise guidance on this matter.
Please assist me on the calculation of the amperage by considering the Service Factor of the motor.

• John Lemau says

Service factor is the percentage multiplier that a motor can handle for short periods of time when operating within its normal voltage and frequency tolerance.SF is intended for unpredictable and brief overload conditions, not for continuous operation or intentional short-term overload.

example :
SF 1.15 = 15% more from motor HP/kW
5HP = 3700Watts
SF = 1.15 = 15%
3700 + 15% = 4255W
So the motor will be loaded to 4255W and current consumed in that load is declared as SFA.

41. Mahendra says

240 hp
292 amp
180 kw
415 volt
3 phase induction motor
I now that par phase amp

42. aju. A says

a 3 phase 15 hp. motor so plz find full load ampere

43. Narottam sahoo says

A 5hp,400v ,3phase motor having 75%efficiency and operating at pf of 0.8 takes a current of ——–A

This site uses Akismet to reduce spam. Learn how your comment data is processed.