cr4 - thread_ starting current calculation

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CR4 - Thread: Starting Current Calculation

http://72.46.236.188/thread/58774/Starting-Current-Calculation[3/26/2013 10:30:22 AM]

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Anonymous

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Star t ing Cur ren t Ca lcu la t ion08/18/2010 4:35 AM

how to calculate the starting current of 3phase ,55kw motor,400v.

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Anonymous

Poster Re: sta r t in g cu r ren t ca lcu la t ion08/18/2010 5:10 AM

With what starter?? DOL or S/D?

SYEDBASHA-

SHAMEEMARe: starting current calculation08/18/2010 5:44 AM

PWSlackGuru

Join Date: Jan 2007Location: In the bothy, 7chains down the line fromDodman's Lane level

Re: sta r t in g cu r ren t ca lcu la t ion08/18/2010 5:11 AM

The locked rotor current is the supply voltage divided by the resistance of the supply cable and the resistance of the winding

it is applied to.

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crossing. Kettle's on.Posts: 18962Good Answers: 454

TornadoGuru

Join Date: May 2009Location: Ketchikan, AK,USAPosts: 12632Good Answers: 452


The motor nameplate will give the FLA (full load amps) or FLC (full load current) of the motor. Another item on the

nameplate will give a code letter that tells the ratio of starting current to FLA/FLC. Multiplying these values gives the starting

current of the motor. What you need to do is not so much a calculation, but rather a look-up of the motor data.

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Hameedullah

EkhlasPower-User

Join Date: Feb 2010

Posts: 191Good Answers: 11


Why dont you use Softwares like Etap, Power Digsilent. You can find easily start current.

Ali18Commentator

Join Date: May 2008Posts: 95


Hi Guest,

The motors' starting current varies differently from motor to motor, as evidence; you sometimes find two motors of two

different manufacturers with the same power ratings, but their starting current is dissimilar in conclusion, there's no

general rule

Regards,

__________________

look for "learning & knowledge" even in Antarctica

Anonymous


it is normally taken as multiple of Coded letter on name plate or if you dont have any thing take 6-- 12 times FLA

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harry potterPower-User

Join Date: Nov 2008Location: IndiaPosts: 334Good Answers: 6


dear ,

You want to find the starting by calculations ? not by refering the manufacturer's guide ?

Motor starting current = V line - line /1.732*Zsc

where Zsc = Impedence of the motor as referred to stator

winding.

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Exploring the Science of Electricity

Anonymous


Moto r s ta r t i ng on D OL

starting current = 4-8 times full load current. Typically taken as 7.5 times FLC

Starting Torque = approx full load torque

Moto r S ta r t i ng on S ta r - de l t a

starting current = 1/3 Starting current of DOL = approx 2.5 times FLC

Starting Torque = approx 33% of full load torque

Moto r So f t S ta r t i ng

starting current = depending on setting (>150% onwards of FLC)

Starting Torque = Depending on the current limiter setting may be as low as 6% of Full load torque.

Moto r S ta r t i ng on VFD

Depending upon

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Users who posted comments:

Ali18 (1); Anonymous Poster (3); Hameedullah Ekhlas (1); harry potter(1); PWSlack (1); SYEDBASHA-SHAMEEMA (1); Tornado(1)

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