Motor Kilowatts

That information will be on the nameplate.

You could measure the amp draw of the motor, while running, to get an approximation.

No,...Only a chart for a ball park size...

https://www.engineeringtoolbox.com/nema-electrical-motor-frame-dimensions-d_1504.html

https://www.engineeringtoolbox.com/NEMA-Frame-Assignments-d_1446.html

Thanks guys. but lets assume that there is no name plate, the name plate is missing or invisible like on my situation, but the motor Voltage is known. The motor cant be power tested because the winding are down to earth. But i want to knw this motor kilowatts. So is the a method or calculation that i can use or do to get the motor kilowatts.

If <...the winding are down to earth...> then the motor is scrap metal and its <...kilowatts...> are zero. Weigh it in, and buy a replacement.

Thanks PWSlack, I want to buy replacement, but i dont knw the kilowatts due to the missing name plate of the motor

Find out the kW required by the kit the motor is driving, eg from supplier's data. If you can do that fairly accurately, select the motor with next higher rating. If you can't, add a safety margin, smaller or larger depending how close you think your estimate is.

Take the motor to rewinder service...

I agree with you,SE

A rewind facility can determine the specifications of the motor,and most places in the USA charge around 2/3 the price of a new motor to rewind the motor,so it would be better for the OP to pursue this method.

I realize you are in a small town, and a rewind facility might not be available locally,but but perhaps you could ship it out to a nearby facility.

Then look elsewhere. There will be a Commissioning record. There will be maintenance records. There will be an equipment manufacturer to contact. There will be a setting on the overload device.

No.

A better way than shaft dia is to find the frame size. This the dimension in mm from the bottom of the feet to the shaft centreline. I assume you know the number of poles. Looking up frame size in a catalogue won't give you a unique kW rating, but it will narrow it down.

You could start by measuring the size of the motor.

Feet spacing, shaft diameter, and height. These can be referenced to frame size using tables found online. The frame size would narrow down the motor power rating to a smaller list.

https://www.google.com/search?q=motor+frame+size+chart&oq=motor+frame&aqs=chrome.2.69i57j0l3.6486j0j7&client=ms-android-verizon&sourceid=chrome-mobile&ie=UTF-8

The motor shaft diameter is an indication of the torque capability. Measure the distance between the holes in the feet, the distance from the end of the shaft and the front mounting holes, and you should zero in the frame size and speed, which then should give you a reasonable Kw rating.

more details on the motor, like construction ODP or TEFC will narrow down the kw rating, the rating is higher with better heat exchange to the air.

As the output of the motor is a function of the voltage applied to its terminals, the quality of the power applied to it and the torque-speed-characteristic-curve of the thing that it is turning, the answer has to be "no".

The shaft requirement depends on the torque to be generated, for a given amount of torque, the watt requirement can vary according to speed and motor efficiency...so for a particular motor, if you had all the required information you could determine watts required for start-up under load, running watt requirement at full load...

Then you would need to know the design of the shaft, characteristics of the steel, hollow or solid shaft, length of shaft, etc....

Then you need to determine safety margin requirement...

https://simplemotor.com/calculations/

https://www.engineeringtoolbox.com/torsion-shafts-d_947.html

You can estimate from the supply circuit amp sizing, or from the size of the internal wire leads. Go by current code to select a motor rated to draw less amps than the supply circuit / wiring will permit.

Given the absence of any form of record that can be indicated to this forum, and installation and maintenance recording is the essence of good practice, one wonders whether the rest of the installation is to any form of local code. The smart money is on “no”.

There is no suggestion of a maintenance spare motor being to hand.

So one must assume that the facility is now out of use until CR4 comes up with a way of getting it running again, which is not what CR4 is there for.

How any facility can be run in such a way is abstruse.

Every motor ever made does some kind of mechanical action by using the energy from a different energy source. Since the nameplate of this defunct electric motor is missing then deriving its attributes from the kinematics of the mechanical load and/or the available electric power is the only option.

What is the motor voltage? What amp rating is the overload protection device? (Wire, circuit breaker, and fuses will all be sized somewhat to considerably larger and thus not be as accurate.)

You should size the motor according to load, there's no guarantee the original motor is correctly sized...

https://www.machinedesign.com/news/motor-sizing-made-easy

Here is a link to help you determine the frame size of your motor.

https://www.engineeringtoolbox.com/nema-electrical-motor-frame-dimensions-d_1504.html

How about figuring this in reverse.

You provide the name of / or the type of machine the motor is for, then we, you, can find the motor (s) that is/are applicable.

Knowing kW alone is not sufficient. It is the speed-torque characteristic to match with the driven equipment requirement, Starting current from the point power system capability to limit the starting voltage dip etc.

If you can make out from the name plate at least the make and Serial No. and year of manufacture - the OEM will generally help with the data sheet of the motor. If the motor is over 20-years old, even the manufacturer is unlikely to hold the data in his archives.

Generally motor sizing is part of driven equipment (compressor/pump/fan) sizing engineer's job during detailed design stage of the project. The O&M manual of the compressor/fan/pump generally include motor data sheet as well.

If the installation is really old, it is wise to replace driven equipment and the drive together as a package.

See-for instance:

https://www.mromagazine.com/features/how-proper-shaft-sizes-are-determined/

Uh, I realize that if this motor powered a generator which then powered other things, then my suggestion may not be totally applicable.

However (and this may still be a bit presumptuous on my part), but if this motor drove only one device, then what is the maximum power draw on that device? Is that information not on the piece of equipment it powered? If it is a commercial device why can't that information be researched? If it is a commercial device why can't you find out what make & model motor they used? The manufacturer either manufactured the motor themselves, or they bought it off the shelf somewhere. That should be very easy to find. If the device was homemade, and/or you cannot determine the current draw, again that part of this advice is meaningless.

Assuming you can find it, the maximum current draw will not tell you the exact motor to buy; but, you could buy the most efficient motor applicable having a sufficient range which covers and exceeds that spec.

Even if it did drive a generator, add up the current draw on all the devices it was ever tasked with powering at the same time, and follow the course outlined above.

More info will help you find the answer to your question.

Is the motor single phase or 3 phase?

(Single phase motors sometimes have the info inside of the wiring cover or wiring box.)

What voltage is the motor?

Determine the Frame size of the motor using the link I provided.

Is there another similar machine that can be used for comparison?

Any other info will be helpful.

Just dismantle the motor and look at the motor winding.

The number of slots, the number of coils and the coil-pitch and the way the winding is made up (one layer / double layer winding), tell something about the number of poles in the motor (and by extension the motor speed).

Measure the rotor diameter and the field length.

The squared diameter multiplied by the field length gives you an estimation about the motor power.

Offcourse, you have to compare the above result with the same result as measured in know motors.

An different way to handle the problem is to measure the cupper wire diameter of the motor winding and determing the number of parallel coils.

Knowing that an acceptable wire current equals to 6 - 8 ampères per squared mm cupper wire surface, you can estimate the nominal motor current.

The motor output power will be equal to : Output power = sqrt (3) x I x U x PF x efficiency.

As an approximation use (power factor) PF = 0.9 and efficiency = 0.8

This method is only valuable for three phase induction motors, with normal cooling conditions (TEFM) and in normal climate conditions (no motor used in cold storage rooms, no motors with water cooling, no motor for extraction hot gasses.)

"... kilowatts of the electric motor by using the size of the motor shaft? ...."

.

This would use the same formula for determining the horsepower of your car's engine using the numbers on the sidewall of your tires.

Where is the maintenance spare motor?