3490 RPM Motors

[StarCat]

Why did some motors which were formerly rated at 3450 RPM jump to 3490 RPM.
What are the reasons, advantages and disadvantages of this?
Looking just today, this model I have bought in the past is now up to 3600 RPM

Electric Motor Whole sale

www.electricmotorwholesale.com

What is this about?

 

[kwired]

Changes in efficiency created less slip? Synchronous speed is 3600 on both those.

Nameplate values are presuming rated voltage and frequency input and rated HP on the output shaft, change any of those and actual output speed can vary some. Less than rated power on output shaft it may even run a little faster than nameplate amps, should never go faster than synchronous speed if frequency remains at 60, if the driven load tries to make it go faster then it will be using power to try to slow it down instead of speed it up or to maintain speed. ADD: Actually it won't be using power but rather transferring power back to the supply circuit, motor basically becomes a generator.

 

[iceworm]

Why did some motors which were formerly rated at 3450 RPM jump to 3490 RPM.
... this model I have bought in the past is now up to 3600 RPM ...

What is this about?​

Short answer - don't know (about the 3600)

Induction motor has 3% - 5% slip. Has to - it can't produce any torque with out slip.

As kw said, 60HZ, 2 pole, synchronous speed is 3600rpm
3% slip is 3492 rpm
5% slip is 3420 rpm
Running unloaded all will be pretty close to 3600 - but not quite. It takes a small bit of torque for the windage and friction

none will turn 3600 rpm

And I'm thinking you already knew all tis

 

[synchro]

The graph on page 5 of Leeson's specs sheet for this motor shows about 3540 RPM typical when developing 3HP, and 3596 RPM no load (zero net torque):

https://cdnmedia.regalbeloit.com/images/d120001/medias/docus/3261/Article_121870.00_DataPack_9.pdf

The vendor may have called it a 3600 RPM motor just to convey that it's a 2-pole motor vs. something else.

 

[Jraef]

The vendor may have called it a 3600 RPM motor just to convey that it's a 2-pole motor vs. something else.

Agreed. I think that listing is just laziness on the part of the seller...

 

[StarCat]

Thanks for all the responses. Calling it 3600 RPM is misleading with respect to former conventions. This is a sign of the times.
I have looked at some slip calculations with 3% being used for that motor as it " was " labeled formerly from 3600 which gives the correct answer.
This particular application is with problems that are getting worked out and is RPM sensitive. In the last I have had to break out tachometers.
Its always interesting when someone replaces a 3450 RPM motor with a 1750 on a DX fan drive.

 

[Jraef]

...
Its always interesting when someone replaces a 3450 RPM motor with a 1750 on a DX fan drive.

It's even MORE interesting when it's the other way around!