FLA Vs Running Amps

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Orerofsirhc

Member
Does anyone know what is the difference between full load amps and running amps is? or where i can find the definition for the two?

Hameedulla-Ekhlas

Senior Member
Does anyone know what is the difference between full load amps and running amps is? or where i can find the definition for the two?

When a motor gives its full rated out put power, the amount of current is called the full load current.
or
The maximum current amount which an equipment is designed for it to operation in a special condition.

When a motor is running at its normal speed without its maximum load, the amount of current is called running current. Or Running current is always at normal motor operation.

LarryFine

Master Electrician Electric Contractor Richmond VA
I thought they were the same thing.

kwired

Electron manager
Full load amps is what the motor will draw at its rated voltage, speed, frequency and horsepower. change any of these and your amperage will now be running amps.

Running amps can be the same as full load amps but the conditions of the power source and load determine the actual amps and are almost never the same as the conditions used to determine the full load amps.

Chamuit

Grumpy Old Man
I've always been under the impression that FLA is the same as MCA which are the running load + 25%.

mcclary's electrical

Senior Member
I agree with Ham's explanation. If you had a large HP motor on a large saw blade, just sitting there idling, not under load,, that would be your running amps.

Now run a big log through the blade and start cutting. The amperage might double. That's your Full Load Amps

iwire

Moderator
Staff member
Now run a big log through the blade and start cutting. The amperage might double. That's your Full Load Amps

No that might be FLA but much more likely it would be RLA.

As kwired said

Full load amps is what the motor will draw at its rated voltage, speed, frequency and horsepower.

While pushing the log through you could, and likely will exceed the HP rating.

mcclary's electrical

Senior Member
No that might be FLA but much more likely it would be RLA.

As kwired said

While pushing the log through you could, and likely will exceed the HP rating.

That makse sense. My example was really poor for a technical discussion. In my example,,,the current being used would eb proportional to many other factors such as speed of feeding log through and alot of others. In other words, if fed to fast, you would start stalling motor and getting more towards locked rotor currents. There can be a huge difference between the two.

iwire

Moderator
Staff member
IMO FLA is an ideal number that will rarely be seen in the field, we use it only to size the OLs.

Few applications require the specific HP the motor is rated for.

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don_resqcapt19

Moderator
Staff member
The running current is exactly that...the current that the motor draws when running and is a variable number based on the applied mechanical load. The FLA is the nameplate amps for the purposes of overload protection and the "table" amps for the purposes of sizing the motor circuit conductors and the short circuit and ground fault protection.

Jraef

Moderator
Staff member
Don has it. FLA is a tested repeatable value, RLA is totally subjective and essentially meaningless, except in context.

What I mean by that is that there is nothing useful that can be done with RLA values unless you are comparing them to a know value or previous value. For example: yesterday the RLA on this motor was 5.3A, today the RLA is 7.9A, therefore today there is more load on the motor.

Orerofsirhc

Member
thank you for all your responses they were very helpful and informative.

jrohe

Senior Member
The running current is exactly that...the current that the motor draws when running and is a variable number based on the applied mechanical load. The FLA is the nameplate amps for the purposes of overload protection and the "table" amps for the purposes of sizing the motor circuit conductors and the short circuit and ground fault protection.

You are not permitted to use the nameplate FLA or RLA for sizing short-circuit and ground-fault protection of motors unless the motor is built for speeds less than 1200 RPM or high torques, or for multi-speed motors. NEC 430.6(A)(1) requires the use of the full-load current (FLC) values listed in Tables 430.247, 430.248, 430.249, and 430.250.

Phaedra

Banned
FLA Vs Running Amps

Whats the relationship between motor turns to amps?
For example: How much more amps would a 14t draw
than a 27t? or 1 less turn will increase amps by how much?

don_resqcapt19

Moderator
Staff member
You are not permitted to use the nameplate FLA or RLA for sizing short-circuit and ground-fault protection of motors unless the motor is built for speeds less than 1200 RPM or high torques, or for multi-speed motors. NEC 430.6(A)(1) requires the use of the full-load current (FLC) values listed in Tables 430.247, 430.248, 430.249, and 430.250.

If you will read my post again I thing you will find that I said to use the nameplate value for the overload protection and the "table" value for the conductor sizing and short circuit and ground fault protection. Maybe my use of the word table in quotes was not clear, but it was intended to mean the tables at the end of Article 430.

jrohe

Senior Member
If you will read my post again I thing you will find that I said to use the nameplate value for the overload protection and the "table" value for the conductor sizing and short circuit and ground fault protection. Maybe my use of the word table in quotes was not clear, but it was intended to mean the tables at the end of Article 430.

My apologies. You are correct.

weressl

Esteemed Member
Does anyone know what is the difference between full load amps and running amps is? or where i can find the definition for the two?

Full Load Amps is the nameplate rating of an equipment, it is the current it is expected to draw at rated load and rated voltage.

The actual load of course varies based on the torque requirements of each driven equipment. Let's say that the calculated horsepower requirements for a pump at the operating point is 7.2 HP. As applications match the standard equipment rating mechanically, it is likely that the selected pump can deliver more pressure/flow than the requirement. So the mechanical engineer has a choice to make and they usually size the pump dirver to the 'end of the curve' of the pump, in this case say 8.7HP. Since there is no such a driver available, next highest HP rated motor is selected and that would be 10HP.

As the result of the above process, you will have a 10HP pump with an actual load of 7.2HP or somewhere in that area. SO your running or operating amperes will be correspondingly less than the FLA would correspond to the 10HP. HP and A ratio is non-linear.

GeorgeB

ElectroHydraulics engineer (retired)
IMO FLA is an ideal number that will rarely be seen in the field, we use it only to size the OLs.

Few applications require the specific HP the motor is rated for.
In the hydraulics business, that is less true. It is not terribly unusual to draw FLA frequently in a machine cycle. We have "horsepower controls" (really torque controls which become HP controls at constant speed) which adjust the pump dynamically (reducing flow once the torque maximum setting at maximum pressure is reached); these will often sit at FLA for extended periods.

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