Need Help With 1 Hp Motor

Harbor Freight tools rate their motors using Shetland Ponies as their horses of choice, not Clydesdales.

Be careful trying to replace your motor with a NEMA (American) sized replacement motor.
The original motor is METRIC sized (frame size currently eludes me), a Nema 56 frame motor has a 5/8" shaft and a Nema 48 frame is 1/2"diameter.
Harbor Freight motors are something like .550" or so (not quite 9/16") so your pulleys won't swap without a sleeved bushing inside it or turning down the 5/8" rotor of the 56 frame one.
Also the mounting bolts are completely in the wrong spot for easy swapping, but this is a machinists website after all so it should be easily remedied.
I believe these are a Capacitor RUN motor, NOT capacitor Start, so as someone else mentioned it might be bad and causing you grief.

The 138* temperature is normal for an electric motor under a load. I didn't see a spec on the nameplate you posted, but MOST motors have a "Temperature Rise of 40*C" (CENTRIGADE) which is 104* F.
You add the Temp. Rise to the Ambient (Air) temperature and you get the average working temperature of the motor.
Some motors actually have a 50*C rating (they get hot enough to fry an egg on but are fairly uncommon in use).
Good Luck
Tommy
 
I read your question with interest. HF is bad about stating hp. Based on the name plate it consumes electric for 1.03 hp .that is theoretical hp based on 100% eff.
Using the standard of 83% that would be .850 hp. That motor is not capable of yielding those results. Based on my experience with HF motors the other people are being generous with .25 hp.
I have a 1942 drill press that is 1/2 hp and the current draw is 7.8 amps, the 1920's ? drill press that is 1/4 hp draws 4.6 amp ,and my 1950's Delta/Milwaukee band saw draws 5.0 for 1/3 hp. I ordered many years ago a 1/2 hp grinder from HF, I could hold the grinding wheel and turn it backwards while on. Don't waste your money on repairs, you would have the same hp. Yes you will squeal when pricing another motor. If it has a frame size you are in luck as that how to get a motor that will fit., if not you will the bench to center line of shaft and the mounting feet hole spacing. Sorry I didn't have better news.
 
I took a look at my own HF bandsaw motor, and here is what I learned: under the hump on the side, there is a start capacitor, necessary to get it going from a dead stop. It is not a run capacitor, which if bad, could have explained your results.

I verified it was a run capacitor by cutting its leads. The motor hummed but didn't start moving. If I substitute a much lower capacitance (5uF instead of 35uFd that comes with it) to simulate a failing capacitor, same thing. But if I then give it a manual shove (under no load, i.e., blade not touching work), it starts up and reaches normal speed. When I let it down on the work (aluminum plate 1/2") it cuts through like butter, as usual. This scenario is typical of capacitor start motors. Bottom line: if it starts up fine, it ain't your cap.

Odds are pretty high the motor is shot, as other problems almost always have other symptoms, which you haven't mentioned (example - most bad switches, wire junctions, power cords and plugs give you intermittent /erratic power, making the motor speed up, slow down, etc., and you might even hear/see/smell the arc - which by the way, can be dangerous to the equipment, not to mention your workshop and yourself.

My bandsaw has given me consistent, decent performance. I buy better blades for it (from Enco, not HF). The motor is fine for the job. You can do better, but not at the price.
 
My busy bee band saw looks similar. Mine would stall also . Turned out to be the brass gear in the transmission. It was so worn the steel worm gear and the brass gear would jam and stall the motor. One day I had left it to cut and it failed to shut off. The motor was really hot and the brass gear was stripped completely. The oil looked like it was liquid brass.
 
FYI
USA made motor are full Horse Power for 24 hours. Some China motors are made like vacuum clearer lock rotor hp
The other part is look for SF 1.1 or higher on the motor this will give extra power when need

Dave
 
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I took a look at my own HF bandsaw motor, and here is what I learned: under the hump on the side, there is a start capacitor, necessary to get it going from a dead stop. It is not a run capacitor, which if bad, could have explained your results.

I verified it was a run capacitor by cutting its leads. The motor hummed but didn't start moving. If I substitute a much lower capacitance (5uF instead of 35uFd that comes with it) to simulate a failing capacitor, same thing. But if I then give it a manual shove (under no load, i.e., blade not touching work), it starts up and reaches normal speed. When I let it down on the work (aluminum plate 1/2") it cuts through like butter, as usual. This scenario is typical of capacitor start motors. Bottom line: if it starts up fine, it ain't your cap.

Odds are pretty high the motor is shot, as other problems almost always have other symptoms, which you haven't mentioned (example - most bad switches, wire junctions, power cords and plugs give you intermittent /erratic power, making the motor speed up, slow down, etc., and you might even hear/see/smell the arc - which by the way, can be dangerous to the equipment, not to mention your workshop and yourself.

My bandsaw has given me consistent, decent performance. I buy better blades for it (from Enco, not HF). The motor is fine for the job. You can do better, but not at the price.

A 35 MFD capacitor is NOT a start capacitor, it IS a run capacitor. Start capacitors have a much higher mfd rating and it is always given as a range of values (124-149mfd, 149-174mfd, 174-208mfd, etc.). For a 1hp motor it would be in the neighborhood of 124-149 mfd or 149-174 mfd it depends on the original engineers calculations when the motor is built. Just look under the cover of your average 1hp sprinkler or pool pump. The motor didn't start because it had an open circuit when you removed the capacitor or you used a 5 mfd capacitor that it is not designed to use. Run capacitor values are more critical than starting capacitor values, because they remain in the circuit at all times. Even a slight change of 35mfd to say a 40 mfd will affect the way the motor works. If of the wrong value the motor will run hot, lack torque and generally not perform well at all. It IS quite possible that the mans RUN capacitor is weak and causing his problem. Any electric motor shop should have a "Capacitor tester" and be able to tell him if his is within spec. Sorry. If you don't believe me Google it for yourself.
 
A 35 MFD capacitor is NOT a start capacitor, it IS a run capacitor. Start capacitors have a much higher mfd rating and it is always given as a range of values (124-149mfd, 149-174mfd, 174-208mfd, etc.). For a 1hp motor it would be in the neighborhood of 124-149 mfd or 149-174 mfd it depends on the original engineers calculations when the motor is built. Just look under the cover of your average 1hp sprinkler or pool pump. The motor didn't start because it had an open circuit when you removed the capacitor or you used a 5 mfd capacitor that it is not designed to use. Run capacitor values are more critical than starting capacitor values, because they remain in the circuit at all times. Even a slight change of 35mfd to say a 40 mfd will affect the way the motor works. If of the wrong value the motor will run hot, lack torque and generally not perform well at all. It IS quite possible that the mans RUN capacitor is weak and causing his problem. Any electric motor shop should have a "Capacitor tester" and be able to tell him if his is within spec. Sorry. If you don't believe me Google it for yourself.

Maybe I'm missing something here, and if you can tell me what it is, I would appreciate it.

I'll grant you that most start caps are higher mFd than run caps. But I just don't see how the OP's cap could be a run cap, for two reasons:

First, it isn't the value of the capacitor that makes it a run capacitor, but how it is used in the motor. The start capacitor is only in the circuit until it reaches typically 75% of rated speed. The value of the capacitance depends on many things, primarily frequency, motor design, and start-up torque required. The first is fixed, the second beyond this discussion, but I think the third, start-up torque, may explain why a relatively low 35 mFd could work as a start capacitor. Assuming you don't start the saw with the blade pressed against the stock, it doesn't take much torque to get it going; you're starting it with no load. Contrast this with sprinkler or pool pump, where you're working against the water from the moment the shaft starts to turn. That's where you need a lot of capacitance and that's where you find it. Same thing with winches, elevators, and cranes: you're starting under a heavy load.

The second reason I'm not convinced is the empirical evidence: the removal (or weakening of the cap) affected only the start-up performance. It had no effect on full speed operation under load. Perhaps I wasn't clear: with the cap out of the circuit, or significantly lower capacitance, the motor hums but does not start, but if I give it a spin, it picks up speed and in a few seconds is up to full speed. I can use it to cut stock at the same rate as when the right cap is in the circuit. From this, it seems clear to me that (1) the circuit was not open (if it were, the motor would not have hummed or run at all), and (2) the cap is a start capacitor (as it was necessary to start the motor) and not a run capacitor (as the motor ran with full speed and power without it). This pattern is the hallmark of a bad start cap (easily verified via your favorite search engine).

Finally, I took your suggestion to Google the ranges for start and run caps. Within the first couple of hits I came across a much lower end range than yours: "Most start capacitors have ratings of 50-1200 uf" - which is to say, not all start capacitors are above 50. So his 35 mFd is not an unreasonable value for a start cap. [http://www.capacitorformotor.com/motor_capacitor.html]

Am I missing something? Maybe you have an better explanation for the results of my "experiment"?
 
Maybe I'm missing something here, and if you can tell me what it is, I would appreciate it.
I'll grant you that most start caps are higher mFd than run caps. But I just don't see how the OP's cap could be a run cap, for two reasons:
First, it isn't the value of the capacitor that makes it a run capacitor, but how it is used in the motor. The start capacitor is only in the circuit until it reaches typically 75% of rated speed. The value of the capacitance depends on many things, primarily frequency, motor design, and start-up torque required. The first is fixed, the second beyond this discussion, but I think the third, start-up torque, may explain why a relatively low 35 mFd could work as a start capacitor. Assuming you don't start the saw with the blade pressed against the stock, it doesn't take much torque to get it going; you're starting it with no load. Contrast this with sprinkler or pool pump, where you're working against the water from the moment the shaft starts to turn. That's where you need a lot of capacitance and that's where you find it. Same thing with winches, elevators, and cranes: you're starting under a heavy load.
The second reason I'm not convinced is the empirical evidence: the removal (or weakening of the cap) affected only the start-up performance. It had no effect on full speed operation under load. Perhaps I wasn't clear: with the cap out of the circuit, or significantly lower capacitance, the motor hums but does not start, but if I give it a spin, it picks up speed and in a few seconds is up to full speed. I can use it to cut stock at the same rate as when the right cap is in the circuit. From this, it seems clear to me that (1) the circuit was not open (if it were, the motor would not have hummed or run at all), and (2) the cap is a start capacitor (as it was necessary to start the motor) and not a run capacitor (as the motor ran with full speed and power without it). This pattern is the hallmark of a bad start cap (easily verified via your favorite search engine).
Finally, I took your suggestion to Google the ranges for start and run caps. Within the first couple of hits I came across a much lower end range than yours: "Most start capacitors have ratings of 50-1200 uf" - which is to say, not all start capacitors are above 50. So his 35 mFd is not an unreasonable value for a start cap. [http://www.capacitorformotor.com/motor_capacitor.html]
Am I missing something? Maybe you have an better explanation for the results of my "experiment"?


I understand your confusion on the matter Monty and while I am NOT an electrical engineer I'll try my best to explain my point.
My father started our motor shop in 1960 (the year I was born) so I can only tell you what we have experienced first hand on the job.
The HF motor in question is what's called a "Permanent Split Capacitor" (PSC) motor.
It uses the Start AND run winding AT ALL TIMES in order to boost the HP rating of the motor (usually done on less expensive motors that do NOT require excessive starting torque).
They do this because Iron (motor laminations) is expensive and so is Copper for windings (Although I'd venture a guess that this HF motor used Copper COLORED Aluminum windings). So by utilizing both sets of coils together the motor is smaller (cheaper to manufacture) and uses slightly less Amperage due to the increased resistance of both windings vs. using only the Run windings.
A PSC motor is used on applications like fans or drill presses and bandsaws and Not on a water pump because as you correctly stated the pump starts under a heavy load and the saw is allowed (or should be allowed) to come up to full speed before it's lowered onto the material to be cut.
By removing or changing the capacitor you are effectively deleting the Start winding from the picture completely, which is why you need to roll it over to start it.
With the capacitor removed you could roll the motor over in EITHER direction and it will run equally well (for the most part). Bandsaw probably won't CUT very well in reverse though I'm guessing. LOL

The major difference between Start caps and Run caps is the Start caps are rated for intermittent duty and the Run caps are rated for continuous duty.
The easiest (NOT SAFEST) way to prove my point would be to insert a KNOWN Start cap in your motor and run it.
KA-BOOM will ensue in a very short order as the cap overheats and fails.

I've included a link to a wiring diagram that shows how the circuit is connected and should help you to visualize what I'm saying.
I hope this clarifies things for you, if not LMK.
Tommy

Skip down to mid page for the PSC motor diagram.

http://eng-electric.blogspot.se/2012/08/microchip-ac-induction-motor_11.html
 
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You guys have raised this discussion/debate, to a level that's way over my head. I'm not complaining, I actually love reading these type of posts, and am glad I was the one to start the ball rolling. SO, now I'm hopping someone will dumb this down enough for me to get 1 answer. Will it help to replace the cap. or not ? A quick review: My motor starts, and spins up to max rpm every time. When cutting a 5"wide, 1"thick steel plate, a tooth caught while breaking through, and the motor stopped rather than spin the belt. this was on the middle pulleys (120sfm). Yesterday, I spent over 3 hrs. cutting 1-5/16" dia. round bar, using the top pulleys (80 sfm) , and no problems except once when the blade got pinched (my fault). But this time, (in the lowest speed mind you) the motor kept turning and the small pulley slipped in the belt (somewhat loose belt tension had not been changed since the plate cut). If changing the cap., which is the limit of elect. motor ability, will give it a little more power, so that it won't stall in the 120spm speed, I will do it. Otherwise, I will follow others advise, and keep it in low speed. Anyone got an answer? Thanks, JR49
 
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