AboutWill Expertise Three phase/ AC DC single phase motors, controls, any problems or failures, motor installation, performance issues, connections. All other electric motors/gearboxes/apparatus. Specialty repair concerns, obsolete motors and solutions. Other mechanical or specialty equipment.
See my profile under Home/electrical at this site
Experience 30 plus years in the electrical motor and apparatus repair industry. VP level management of repair facilities, current owner of my own specialty repair and consulting firm.
Organizations EASA, IBEW [retired], other specialty organizatons, Lubrication, Vibration EDI, Triboelectric Councils
Publications Currently fielding concerns at this site under "Home Electrical"
Education/Credentials 4 year technical, College level specific courses, EASA repair courses, vibration analysis electronic and electrical trade school.
Question What is the difference between the less expensive compressor type motor and the more expensive tool motor, like for a table saw? When shopping for used motors, what do you look for on the name plate to tell the difference?
Thanks,
Q
Answer Compressor type..........maybe you are saying condenser fan motor? The rather inexpensive motor with the capacitor sometimes located off the body of the motor?
Versus table saw motor with one or maybe two cans for capacitors.
The cheaper one I think you want to know about, is a PSC Motor or Permanent Split Capacitor. The cap stays in the circuit as kind of a power factor improvement device.
Those are used for light starting loads like a fan. Many of them, in the real low horsepower ratings, you can stop with your hand. DO NOT TRY IT.
The table saw is a capacitor start or capacitor start/capacitor run. On a saw if it will cut through knots and tend NOT to stall, lots of torque.
The first capacitor puts the start winding out of phase with the run and creates rotation. The cap start/cap run does the same thing with the run cap adding power factor.
When shopping for used motors, you need to know the application it will drive.
Motor application is a science of it's own.
Are you needing one for something in particular? Or do you just buy them and resale?
Lots of used motors are some kind of, out of the ordinary design.
NEMA the manufacturer's standards, have general purpose motors rated by size to HP, RPM, Torque and so on.
Used motors usually come off something they were built for, that, and nothing else. Although you can hang a coupling or sheave on one, they are awful hard to match up to a standard saw or tool of some significance.
The table saw looking motors are probably the better choice to have some flexibility, for building a grinder or something.
The other round body cheap motors are not good for much but fans and usually are called HVAC motors...fan motors.
When looking for any motor to buy, don't buy it unless you know how to run it, however many speeds it might have. And it must have the capacitor with it, and the data on the capacitor must be known or readable.
No cap and you will have a hell of a time finding the right one.
A bunch of wires hanging out with not diagram makes it worthless too.
On the nameplate the "better" motors will have a "T" or real old motors will have a "U" at the end of the frame size field. Like 143T, or 256U. That will nearly always be a NEMA design, general purpose motor.
If you are looking for something to run off household current, you have to have a single phase motor. In the phase field, unless you are reselling to industry, you need 1 phase.
It should also have standard voltage ratings like 115, 220, 230. Not voltage ratings like 380 or 190 or 575.
If you find a motor with a decent plate on it, look up the model # at a variety of sites that sell motors, or the manufacturer's site.
$15.00 to 20.00 per HP on non guaranteed motors.
If you are looking to build something let me know what and I will try and guide you.
In general you are looking for standard voltages, motors with a base or feet to bolt it down, wiring diagram, capacitor included with data.
Double shafted motors are usually some freak thing, but some can be made to run like a grinder on one end and a buffer on the other. But they are usually some kind of special, no good for anything.
Motors with shafts that have threads, are tapered, real short, not too good.
Just remember the the little round compressor motors are really condenser fan motors and good for fans only.
When you look in an air conditioner unit outside your house, you will see the cheap little fan motor. The motor that runs the compressor is usually contained in a black enclosure, and is cooled by the refrigerant. They are hard to size to another air conditioner also.
I have bought and sold used industrial motors for years.
It is tricky business. They are sometimes near grounded, the bearing housings are trashed and they stuff heavy grease in the ends to cover the noise.
If you are out at these sales and buying motors, and want to go to the trouble of sending me the nameplate data, I can tell you what is good, bad and maybe what you can get for them.
But if you can't watch them run, you could have a great frame, and crap, wore out, motor. You can download this for free, or it used to be free:
I have no affiliation with it. Or go to ebay and get a couple used ones.
NOW DC You most likely don't want DC, however they are the most rugged and will maintain torque at low speeds. Hard to contol and the controls are pricey.
These are motors with the brushes. If you find some of those, let me know what they are.
If you find a batch of big industrial motors, let me know.
If you will go to the trouble of writing EVERYTHING OFF EVERY NAME PLATE, I can help you buy them and get rid of them. But hauling becomes an issue.
OLD MOTORS AND FANS ARE sometimes worth a fair price. so let me know on those too.
Write me back and let me know what you are doing with motors and I can help you better.
