No motor nameplate

Hey all,

Many times I am called to replace motors that have their nameplates missing, covered in rust, or just unlegible.

Obviously the mechanical side of things aren't for me to spec. I look at the overload to see what it is set at, but this is often been cranked up over the years. I look at the fuses or circuit breaker, also check cable size, I measure the loaded amps, but sometimes the motor is burnt out so this is not possible. Sometimes I just look at the physical size and go off that, but that has bit me a few times over the years. Remeber guys that these are the worst case motors, that many of you are familiar with, so no documentation, no on site knows anything about it...

So, how do you make a correct decision on what to replace with?

Thanks in advance for any ideas to help me.
Nathan

Certainly NEMA motors and probably also IEC motors have a hp assignment table which, given the frame size, limits your choices as to base speed (poles) and hp or kw. A motor shop can determine visually how many stator poles are wound into the motor pretty much giving you the hp or kw and the base speed for the machine.

I am assuming that 50/60Hz is not an issue.

Hmmm Ouji board?? Throw a dart at the wall?

How big are these motors 10 100 1,000 HP??

If you can measure the mount dimensions, clearance from shaft to base plate, shaft dia can you then go back to NEMA look up these values and take a better guess? Course the motor may be old and does not fit into the charts.

The other thing that comes to mind is measure the load torque with a torque wrench. IF you can get into it of course. Now all you need to know is how fast. Surely they might have SOME inkling how fast the shaft must go.
Then HP = Torque x RPM / 5252

The thing that irritates me the few times I have gotten into messes like this
AND they just shrug their shoulders when asked for information
AND they were the boobs that painted over the nameplate or destroyed beyond all legibility
AND they threw away the manual
is that when I guessed wrong they were lightnin quick to point fingers and cry the blues over how much I cost them.

Dan Bentler

leitmotif said:

The thing that irritates me the few times I have gotten into messes like this
AND they just shrug their shoulders when asked for information
AND they were the boobs that painted over the nameplate or destroyed beyond all legibility
AND they threw away the manual
is that when I guessed wrong they were lightnin quick to point fingers and cry the blues over how much I cost them.

Dan Bentler

Click to expand...

Exactly why I posted my question.

By the way only talking small motors, no bigger than 22kW

Had the re winder bail me out a few times, the torque wrench is a handy idea for smaller motors.

I found a good website during my travels to answer my own question. Its a good refresher for the sparkies out there.

http://www.lmphotonics.com/

HJTRBO said:

Hey all,

Many times I am called to replace motors that have their nameplates missing, covered in rust, or just unlegible.

Obviously the mechanical side of things aren't for me to spec. I look at the overload to see what it is set at, but this is often been cranked up over the years. I look at the fuses or circuit breaker, also check cable size, I measure the loaded amps, but sometimes the motor is burnt out so this is not possible. Sometimes I just look at the physical size and go off that, but that has bit me a few times over the years. Remeber guys that these are the worst case motors, that many of you are familiar with, so no documentation, no on site knows anything about it...

So, how do you make a correct decision on what to replace with?

Thanks in advance for any ideas to help me.
Nathan

Click to expand...

In our case in New Zealand.
The new 3 phase motors will fit the DIN standard that is applied to all motors for the last 30 years.

For Din standard motors measure the distance from centre of motor shaft to the base, this will give you a frame size of say D100 or D132 as two examples.
The number 100 or 132 is measured in millimeters

Then measure the distance from fixing bolts to shaft end.
Measure shaft diameter, then look up a motor table chart and you will find very few motor choices left to chose from.

Then if you know the speed of the motor you tend to get one choice or at worst a second choice of a very close KW rating.

Now if the motor is burnt out you will need to determine the speed from the number of poles by looking at the windings inside the motor.

If this motor is older than 30 years it will follow the BS standard, then it becomes more of a guess, as they tended to be slightly larger in diameter and slightly shorter for the same KW or HP rating.

Cool, just the answers I was after.

Thanks to all who replied.

Nathan



P.S. Good win to the Sea Eagles. Suck to be a Storm supporter ha ha!