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8 comments
Anonymous Poster #1

LRA, RLA Question

12/30/2012 12:47 PM

Why A/C motors identified by LRA , What different between LRA & RLA

what physical meaning for each one .

thanks

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#1

Re: LRA ,RLA ,

12/30/2012 1:25 PM

Look them up on Wiki!

Or, go here:

Search all of CR4

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#2

Re: LRA ,RLA ,

12/30/2012 1:43 PM

LRA is Locked Rotor Amperes (max current spike during a motor start)

RLA is Rated Load Amperes (same thing as FLA)

FLA is Full Load Amperes (fully loaded motor current)

http://answers.yahoo.com/question/index?qid=20100609144013AAynIjs

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Anonymous Poster #1
#3
In reply to #2

Re: LRA ,RLA ,

12/30/2012 2:02 PM

thank you JPool , but why these expression are mostly used with air conditioning compressors.

for example we said 95 LRA compressor , why not identified by KW or HP as ordinary electric motors

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#4
In reply to #3

Re: LRA ,RLA ,

12/30/2012 2:20 PM

I really don't know, I looked it up as Lyn suggested in post 1.

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#6
In reply to #3

Re: LRA ,RLA ,

12/30/2012 8:04 PM

I believe it has to do with when the compressor tries to start but can't. Such as high pressure or possible liquid lockup. One example is compressor is running a power glitch stops it. Then tries to restart, but can not, because it can not overcome the running pressure. Then the thermal overload trips. Once the pressure in the system equalize then it can start.

Found this I could not say it any better.

"Locked Rotor Current is a good approximation of the short circuit current that a motor will add to a short circuit on the power system. When a short occurs, the motor acts like an induction generator and delivers current to the fault until the energy stored in the motor's magnetic field and spinning rotor is dissipated. The current does not last long, but it must be accounted for in short circuit calculations.

Knowing a motor's locked rotor amps (LRA) and acceleration time helps in selecting upstream breakers. We make sure the circuit breaker or fuse can supply the locked rotor amps long enough to get the motor load up to speed and that it will trip if locked rotor amps continues beyond the allowable stall time."

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#5

Re: LRA, RLA Question

12/30/2012 2:44 PM

RLA is RUNNING LOAD LRA ARE THE MOST AMPS IT CAN TAKE BEFORE you harm the windings

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#7

Re: LRA, RLA Question

12/30/2012 10:55 PM

Hi there

LRA means : Locked rotor Amperes, Current require to move rotor, when it is in static condition.

RLA: rated Load Amp. Which means, when your motor reaches full load, Current consumption will known as RLA

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Anonymous Poster #2
#8
In reply to #7

Re: LRA, RLA Question

12/31/2012 9:20 AM

See post #2

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Anonymous Poster (2); Fredski (1); JPool (2); lyn (1); metalSmiths (1); rayketul (1)

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