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Anonymous Poster

Calculating Current for Three-Phase Motors

06/17/2008 2:27 PM

I would like to know how to calculate the full load current and lock rotor current of a 3-phase motor ,480V, 62% efficiency and 84% power factory?
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JRaef
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#1

Re: Calculating Current for Three-Phase Motors

06/17/2008 6:56 PM

Full load current is not calculated, it is measured. The other data is calculated from that.

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nesubra
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#2

Re: Calculating Current for Three-Phase Motors

06/18/2008 2:51 AM

Kw Of Motor/Voltage in KV*Power factor*1.732*motor eff

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Anonymous Poster
#3

Re: Calculating Current for Three-Phase Motors

06/18/2008 3:00 AM

FOR CALCULATING FULL LOAD CURRENT, YOU MUST HAVE OUTPUT POWER RATING OF THE MOTOR WHICH YOU HAVE NOT GIVEN. Assuming that 84% is power factor (0.84) in place of power factory (if i am right).

AFTER GETTING POWER RATING

USE SIMPLY THE FORMULA

I(full load) (line current) = P(output) / (Sq. root (3) x V(line) x p.f x efficiency)
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PWSlack
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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#4

Re: Calculating Current for Three-Phase Motors

06/18/2008 7:35 AM

As a rule-of-thumb, lock-rotor current exceeds full load current by a factor of 5.

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