Somtimes My Clutch Motor Runs Backwards And Sometimes Forwards. Why?

[LoveToLearn]

No,you don't want the belt to slip,adj it so it has 1" of play,a smaller motor pulley 2" will help too.

Ok. Is that 1" of play at the foot pedal or 1" between the clutch disc and the pressure plate?

Thanks

LoveToLearn

[Wizcrafts]

Ok. Is that 1" of play at the foot pedal or 1" between the clutch disc and the pressure plate?

Thanks

LoveToLearn

Belt play is usually measured half way between two end points. This means about half the distance from the motor pulley to the machine pulley. In practice, I usually set the play at table level, at the belt slot, behind the bobbin winder wheel. If you don't have a bobbin winder on the table, just figure where the 50% point is and push inwards on the belt. If it deflects between 1/2 and 1 inch, it has enough slack. If the belt slips, tighten it until it stops slipping.

[TinkerTailor]

I have been wondering why guys with the servo motors also add speed reducers? I thought the servo motor provided totall speed control.

LoveToLearn

When i got my 5100, it was set up on the middle pulley of the 3 step speed reducer. I had to slow the motor down all the way to get even close to stitch by stitch sewing. I found that when the motor was this slow, it lost modulation and was more like a 3 speed. After i switched to the smallest pulley, i turned up the motor quite a bit, now my slow speed is slower than was possible on the other pulley, however my top speed is faster and it is a way smoother transition from slow to fast.

In other words, my motor can go slow, but it likes it a little faster. The speed reducer allows this. Plus the torque as Art said.

Edited February 25, 2016 by TinkerTailor

[dikman]

When i got my 5100, it was set up on the middle pulley of the 3 step speed reducer. I had to slow the motor down all the way to get even close to stitch by stitch sewing. I found that when the motor was this slow, it lost modulation and was more like a 3 speed. After i switched to the smallest pulley, i turned up the motor quite a bit, now my slow speed is slower than was possible on the other pulley, however my top speed is faster and it is a way smoother transition from slow to fast.

In other words, my motor can go slow, but it likes it a little faster. The speed reducer allows this. Plus the torque as Art said.

I've noticed the same thing with my servos, if I can increase the minimum speed setting of the motor while keeping the overall speed of the machine low then it runs smoother.

[LoveToLearn]

so servos need rpm to make power too then. When I read about servos they say in the ads that they make the same torque at every rpm but I always suspected that cant be true.

[TinkerTailor]

so servos need rpm to make power too then. When I read about servos they say in the ads that they make the same torque at every rpm but I always suspected that cant be true.

They do make the same torque, it is the smooth change from one rpm to another that gets lost at the lower speed settings. It may not effect more expensive servo motors and may be related to the resolution of speed sensor in the controller. With the motor shaft turning faster, it can sense rpm more accurate and thus adjust it smoother when you step on the pedal.

Also, a speed reducer does not change the torque the motor puts out. A motor only has so much energy, which is a balance between torque and speed. It operates within a designed range for the load and speed most want it to be used for. We want more power and slower than they are designed for, so enter the speed reducer. It uses mechanical advantage after and independent of the motor to increase torque at the expense of speed, which was unwanted anyways.

With enough speed reducers, and assuming very little friction in the system, a sewing servo motor could lift a locomotive, it would just take a very very long time.

Edited February 25, 2016 by TinkerTailor

[DrmCa]

Can you post the pictures of your motor showing the wires and capacitor? I am intrigued!

The 3 phase motor powered from 1 phase needs a capacitor to run, and direction is determined by connecting the 3d terminal via the capacitor to the phase or ground.

Yours running in different directions with or w/o a cap makes no sense, let's see what it looks like.

I took the cover off the back of the motor and removed the capacitor. I put a voltmeter across the terminals with the meter set at 600v ac and got no reading. Then I started the motor with no capacitor and it ran the same as it did before. So the capacitor was doing nothing. I think I need a new cap to tell the motor which way to start. I dont even know if the cap that was in there is the proper cap. I wish I could get some part numbers for the cap and the wearable clutch parts. I would have a good motor then. Then I need a small motor pulley which is 15mm bore and about 35 to 45 mm diameter 3V and a speed reducter which I will make. I have been wondering why guys with the servo motors also add speed reducers? I thought the servo motor provided totall speed control.

LoveToLearn

[LoveToLearn]

It starts and runs whether its in or if I remove the cap completely and set it on the table. Sometimes it starts clockwise and other times it starts counter clockwise. It is a single phase 1/3hp 3.7 amps 1750 rpm motor. I dont see any centrifugal switch and I hear no click when its winding down when I shut it off like on the table saw in the garage.

Edited February 25, 2016 by LoveToLearn

[LoveToLearn]

tag

motor

Edited February 25, 2016 by LoveToLearn

[Art]

I guess I and most everyone else is saying to themselves that you ain't got the chops to be fooling with this thing. I am not going to tell you what to do, it is over your head. The cap you see is part of the circuit that consists of the start winding in the motor (Aux on schematic) and the start capacitor, and is switched in by the start relay (box with dashed lines), the start relay only switches in the start circuit for a short time then goes to the main windings directly. The following is usually the problem, start relay (box with dashed lines), start winding (not usually), or the start cap. On this model the cap is a 7.5 µF used as a start cap (if the schematic is correct) available at Grainger. This is as much as i can provide for you.

If the start relay is toast (probably) then it will never switch in the start circuit, and just leave the mains switched in and the motor will go whatever way it goes. Sound familiar?

Art

[Northmount]

The capacitor with its winding shifts the phase angle of the magnetic field, so that 2 rotating magnetic fields are produced in the stator and pulls the rotor around, causing it to rotate. If this cap and winding are not energized, the motor can start in either direction, or sometimes just sit there and hum. The cap and winding are commonly referred to as the starting winding. If the capacitor is faulty, or the circuit is broken anywhere between its terminals, it won't start reliably.

If you have an ohm meter, you can test the continuity of the winding and its connections. Power must be off for this test, or you'll let the smoke out of your meter. The resistance should be relatively low, probably less than 50 ohms. You may be able to test the capacitor with the ohm meter too if it is an analog type, moving needle, not digital display. With the ohm meter set on the highest resistance range, you may see the needle kick upscale and then settle back to infinite resistance. What you see is the charging current. If you reverse your ohm meter connections, you may see the needle kick to a higher value, then settle back again. You just discharged and charged the capacitor in the opposite direction. If the meter behaves like this, you can be reasonably sure the capacitor is working. If not, the test may be inconclusive, but tends to indicate the capacitor is faulty. Capacitors may have some leakage current, which is normal, so the ohm meter may not settle at infinity, but should settle at a high value of resistance.

Or instead of trying to test the capacitor, just go buy a new one, assuming you have tested the start winding and found it to be okay.

During your tests, for each component, no other components should be connected to the one you are trying to test.

Tom

Edit

I see Art has posted as I was typing this up. I agree with him. Up to you as to whether you can do any testing, safely.

[Art]

Yo, Short the cap terminals before doing anything.

Art

[mikesc]

Been a while since I last logged in, been catching up ( reading threads from 2015 over the past few days )..I agree with Art and northmount..fooling with this ( unless you really know what you are doing with electrics ) could let some important smoke out..from the meter, the motor ..or even yourself..

Buy a replacement cap and fit it..don't "test" the old one..

or..

better yet..

buy a servo motor from one of the dealers on here..

Keeping the smoke in is vital..

[Wizcrafts]

I am worried that this experiment isn't going to end well for our gentle new member...

[LoveToLearn]

The capacitor with its winding shifts the phase angle of the magnetic field, so that 2 rotating magnetic fields are produced in the stator and pulls the rotor around, causing it to rotate. If this cap and winding are not energized, the motor can start in either direction, or sometimes just sit there and hum. The cap and winding are commonly referred to as the starting winding. If the capacitor is faulty, or the circuit is broken anywhere between its terminals, it won't start reliably.

If you have an ohm meter, you can test the continuity of the winding and its connections. Power must be off for this test, or you'll let the smoke out of your meter. The resistance should be relatively low, probably less than 50 ohms. You may be able to test the capacitor with the ohm meter too if it is an analog type, moving needle, not digital display. With the ohm meter set on the highest resistance range, you may see the needle kick upscale and then settle back to infinite resistance. What you see is the charging current. If you reverse your ohm meter connections, you may see the needle kick to a higher value, then settle back again. You just discharged and charged the capacitor in the opposite direction. If the meter behaves like this, you can be reasonably sure the capacitor is working. If not, the test may be inconclusive, but tends to indicate the capacitor is faulty. Capacitors may have some leakage current, which is normal, so the ohm meter may not settle at infinity, but should settle at a high value of resistance.

Or instead of trying to test the capacitor, just go buy a new one, assuming you have tested the start winding and found it to be okay.

During your tests, for each component, no other components should be connected to the one you are trying to test.

Tom

Edit

I see Art has posted as I was typing this up. I agree with him. Up to you as to whether you can do any testing, safely.

I have already tested the cap as I mentioned. The first thing I did was discharge it. (high school electricty class capacitor demonstration). There was no discharge. Then I tested the cap and there was no continuity at any point. the cap is bulging slightly at the top. (not a good sign)

I dont see any safety issues. There is no smoke in the cap because it is dead and cant hold smoke anymore, it is sitting on a bench. The machine is not plugged in so at this moment there is no smoke in it. Im going to test the windings as indicated. If it passes ill get a new cap. Does the one in the pic look like the right specs for this motor? 350VAC and 7.5 MFA. So it is possible that a dead cap can be solely responsible for this random direction when starting? Good to know.

Edited February 26, 2016 by LoveToLearn

[DrmCa]

This is not a dead cap case - if the cap had a short, the motor would be overheating.

If the cap lost capacity due to a cold joint, the motor would not start.

This is the case of a DOA motor.

Send the motor to the scrap yard and get 30 cents/lb for it, and buy a Family 550Wt servo motor instead.

It obviously has an intermittent short somewhere in one of the coils, therefore a toast.

Edited February 26, 2016 by DrmCa

[Ole South]

@DrmCa:... probably IS the start cap. (*Note the caveat that follows) He could have a shorted winding but that generates significant heat/smell and this motor does start... not the correct direction but that's the Start capacitor's job in a single phase ac motor: though Art has a point with the starting relay. If bad and it doesn't de-energize it can fry the start cap causing the electrolyte to overheat and expand.

@LovetoLearn: Swelling (visible in the last picture) indicates the electrolytic inside the cap is expanding (I.E. failing) this is an old motor, *BUT.... the cost of the cap probably will equal or exceed a down payment on a new motor. Retail is probably $15-30.00 usd. Do you have a friend in A/C Heating? Caps like these are used in most air handlers and A/C condensing units. An A/C tech can probably source a substitute for you and steer you down a safe path should you choose to continue to try and resurrect this beast..

Me?... I'd plug in a substitute and stand well back as I power the motor up.... but I've done this before. Sparks flying make the heart beat faster! And often precede the rapid loss of aforementioned smoke necessary for proper operation of electrical components.

Edited February 26, 2016 by Ole South

[LoveToLearn]

. ...

If the cap lost capacity due to a cold joint, the motor would not start.

the motor starts and runs the same with or without the cap installed.

[Art]

Got to love it....I gave you a link to a new cap at Grainger. It's 8 or 9 bucks. Just replace it to see if that works.

The effect will be the same if the cap is short or open, it will spin in either direction because the start circuit won't work. Replace the cap. If you take the cap out, no matter if it is good or bad, it will disable the start circuit and the run circuit will turn it whatever way the motor is inclined to run. Read Tom's reply and just replace the cap. If that doesn't make it run correctly, take the new cap out and take the motor to the scrap heap. Take the new cap to one of 20 or more dealers in Florida who will have a pile of clutch motors that do work in their back room and trade for a used clutch motor that does work.

Electrics are funny, if the start circuit doesn't work, you can take parts of it in and out and the effect will be the same, it will start using the run circuit in a rather random direction. Kind of like expecting a different outcome from the same input, what did they call that?

Art

[LoveToLearn]

Got to love it....I gave you a link to a new cap at Grainger. It's 8 or 9 bucks. Just replace it to see if that works.

The effect will be the same if the cap is short or open, it will spin in either direction because the start circuit won't work. Replace the cap. If you take the cap out, no matter if it is good or bad, it will disable the start circuit and the run circuit will turn it whatever way the motor is inclined to run. Read Tom's reply and just replace the cap. If that doesn't make it run correctly, take the new cap out and take the motor to the scrap heap. Take the new cap to one of 20 or more dealers in Florida who will have a pile of clutch motors that do work in their back room and trade for a used clutch motor that does work.

Electrics are funny, if the start circuit doesn't work, you can take parts of it in and out and the effect will be the same, it will start using the run circuit in a rather random direction. Kind of like expecting a different outcome from the same input, what did they call that?

Ar

Got to love it....I gave you a link to a new cap at Grainger. It's 8 or 9 bucks. Just replace it to see if that works.

The effect will be the same if the cap is short or open, it will spin in either direction because the start circuit won't work. Replace the cap. If you take the cap out, no matter if it is good or bad, it will disable the start circuit and the run circuit will turn it whatever way the motor is inclined to run. Read Tom's reply and just replace the cap. If that doesn't make it run correctly, take the new cap out and take the motor to the scrap heap. Take the new cap to one of 20 or more dealers in Florida who will have a pile of clutch motors that do work in their back room and trade for a used clutch motor that does work.

Electrics are funny, if the start circuit doesn't work, you can take parts of it in and out and the effect will be the same, it will start using the run circuit in a rather random direction. Kind of like expecting a different outcome from the same input, what did they call that?

Art

Hey Art, where is that link you mentioned?

[Art]

available at Grainger.

From my prior post.

Art

[LoveToLearn]

where is the start relay? I dont see one in there do you? Also that link specifies a run capacitor. Do I want a start capacitor or a run?

Edited February 26, 2016 by LoveToLearn

[Art]

That is the exact same cap you have in there. You really don't have a clue do you? We're done.

Art

[LoveToLearn]

If you enjoy denigrating others then indeed you and I are done.

[Art]

How many times do people have to tell you exactly what to do, and you ignore them, till they get the impression they are speaking to a wall?

Art