Today I are been mostly thicknessing oak.
I use a Scheppach planer/thicknesser (a combined jointer & planer, in American) which has a 230 volt single phase 3HP induction motor. After thicknessing a fair amount of oak boards today, I switched the machine off whilst I had a coffee. On pressing the green button, on my return some 10 minutes later, I merely got a hum and no rotation of the knife block, although the auto start on the dust collector worked OK and no fuses blew or tripped.
So, I took the covers off the drive and motor housing to check the drive train – nothing sticking and no rough bearings. I tightened the drive belt a tad (it was already OK really) and checked the wiring (no problems as far as I can see – I have no meter and wouldn’t know how to use it, anyway, to check motor circuits).
The machine, including the motor, spins normally when given a hand-shove. It doesn’t require any great force and the block feels to me like it is turning with exactly the same degree of resistance as when the machine was new.
The motor was hot after the last session – just about touchable. Is that normal? It’s fan is rotating and not blocked.
When I switched on (getting the hum) then yanked the drive belt, to spin the motor, off it went running as normal. I proceeded to plane another load of oak, no problems.
Well, I can’t be having the guard off the drive belt and giving it a manual tug to start it. So what do you think might be the problem, motor experts? Is there something amiss with the black thingy attached to the motor. I believe this provides some kind of starting current…..?
Any suggestions gratefully received.
Lataxe
Replies
It could be the capacitor (black thingy) or the centrifugal switch. You can access the switch by disassembling the motor. Check for burned pitted contacts etc. A motor shop should be able to test the capacitor for you.
Two possibilities, the more likely is the starter switch is hung up. The starter switch is inside of the motor. The second is the capacitor, probably the black thing you mentioned, has failed and needs replacing. If you aren't comfortable with taking the motor apart to track down the problem and repair it, then the motor needs to be removed and taken to a motor repair shop.
A stuck switch is often repairable with just cleaning, a failed capacitor needs to be replaced but that isn't expensive in the U.S., Euro parts seem to be overpriced.
John White
As others have said this is normally a dirty switch or the weights have moved out of range on the shaft. On my old craftsman saw all you had to do was push them back along the shaft. Back to normal for 12 months after that.
If your motor is like several of mine, there is a chance that a small chip of your oak may have been drawn into it and lodged itself between the contacts of the start switch so it can't close. If you have a source of compressed air, you might be able to dislodge it by getting the motor to run briefly (enough to open the contacts) and blasting air through whatever openings in the motor housing you can get to. I'd try that first.
If that isn't successful - and it might not be, since that area can sometimes get oily - the next step would involve taking the motor apart. If the switch is found to be clean and in good working order, you might need a new capacitor thingy.
Checking the capacitor doesn't require an expensive meter or a lot of complicated steps. If you can borrow a simple multimeter with an ohms scale, you can use the method found at
http://www.applianceaid.com/micro4.html
If the capacitor checks out there may be a problem with the start winding, which would likely involve a trip to the motor shop. But as noted by others, the problem is more often just the switch.
Regarding the temperature of the motor, if it's touchable, it's not too hot. There may be a temperature rating given on the nameplate.
Good luck, please keep us posted.
Dan
David,
Any chance of a picture of the motor and the manufacturer's plate? Then we can establish exactly what type of motor it is and avoid undue speculation. For example, 1)if it ####is TEFC (totally enclose fan cooled)type there is no need to suspect that the centrifugal starting mechanism is "dusty".
2)If it is a capacitor start and capacitor run type, there will be no centrifugal starting mechanism. A picture will show this i.e we will usually see two capacitor tubes on the motor casing- but some have the capacitors inside the works.....In which case the manufacturers name/spec plate will tell us....
3) Is the machine equipped with a magnetic starter switch with thermal overload protection? Note-I said "machine" and not "motor".
Anyway, being only vaguely familiar with Sheppach, I tend to think that it will be as in 2) and accuse a capacitor.
How hot can the motor get? As a very general rule: if you cannot hold your hand on it then it is ailing, and if it is smoking and emitting that special smell then it is history. Doesn't sound as if yours is at death's door yet-did it cool down a bit when you ran it after the tea and scones?
Philip,
Herewith some pics of the dismounted motor. Methinks it is sealed but maybe them funny looking nuts would release an end plate. There is no explosion of the motor lump shown in the manual, although the drive pulley comes off. Every other part of the machine is exploded into a thousand parts, each with a number.
When the motor is connected and started on the bench there, it comes up to speed in no time and runs very quietly. I did tap the casing with a rubber mallet, both ends when stood end(s) up - in the hope that a sticking internal part might free itself. Maybe this has worked but I won't know until I remount it in the machine and try to start with the drag of the planer block.
That drag seems minimal to me. Yet when I tried to start the motor this morning, from stone cold, it wouldn't go even with a helping tug or two on the drive belt.....
The manual, as well as warning off all but qualified electricians from motor-mending, notes that there is both an internal motor brake and an automatic cut-off switch should the motor get too hot. That switch has never tripped, despite some pretty heavy planing and thicknessing sessions.
The manual also notes that the whole motor, with capacitor(s) and mag no-volt release switch, must be returned should any servicing be required.
So, I will run/start it a few times more on the bench then remount it and see if it has solved the problem.....
Meanwhile, thanks all for the many helpful suggestions and advice.
Lataxe
The fact that it comes up to speed now suggests that there is at least a fair possibility that the motor has a stuck starter switch that freed up from being banged around a bit. Chances are, however, that it will not stay fixed for long.You might take off the cover on the black box that holds the capacitor and take a look. Capacitors will occasionally split or otherwise show obvious signs of failure when they die, you might even get lucky and find that there's a loose wire that just needs reattaching.John White
John,
Thanks for the advice. I did think of taking off the black box but I'm very wary of capacitors and their connections, as they hold that big charge which may want to leap into my finger tip. Then I will dance about a bit or possiby lie down for an enforced rest. :-)
As you and others have said, the starter switch would seem the most likely culprit. I could try taking that end plate off, assuming I can find a driver bit for those tag-nut thangs. But if the motor is essentially sealed, I'm thinking that wear rather than dirt is the likely underlying cause.....? If so, a refurbishment or replacement by Scheppach may be the best option.
The machine is nearly 10 years old and has planed/thicknessed an enormous amount since I got it. It's also a machine that tends to have the motor running for lengthy periods of time, unlike the similar motors on my TS, bandsaw and belt sander. I don't know if that's good or bad for a motor's internals. The thing is, it runs very smoothly and quietly on the bench, there.
I'll replace it in the machine and see what happens when it has to start up with the belt attached to the planer block.
Lataxe
Since it only sees alternating current, the capacitor won't bite.
Ow, that is an untruth! It has not been my experience at all....Philip Marcou
It depends on past history. The capacitors will have whatever charge was on them at the momemt they were disconnected from the power source (minus what bleeds off over time).
The capacitors on induction motors don't store that much energy. You can get a painful jolt, but it won't send you across the room.
-Steve
David,
I can't read the plate. Now that I see it I advise you to take it to a suitable shop, and don't try to take it apart. It has aluminium body casing which can be easily damaged if you don't have suitable tools.
Since you sat it will run without a belt on the pulley but not if even a small load is placed on it , I think it has a capacitor problem. I am not at all convinced that it has a mechanical centrifugal starting mechanism, so in the absence of this it requires an electrocutor to check it out with his box of tricks and maybe fit a new capacitor.
Perhaps contact the Sheppach vendor for details of a suitable service agent.
P.S : No need to fear capacitors- you can safely discharge them by contacting terminals to an earth (other than yourself), using an insulated screw driver or wire. And you can check if they are dead with a test meter.Philip Marcou
Philip,
The PT is back together again but the problem persists - I need to tug the drive belt to stop the hum when the green button is pressed to make the thing take off. Once going it runs and planes fine.
From schooldays (600 years ago) I vaguely recall that an induction motor needs to be turning to generate power. Presumably this is the reason for the starter thingy and the jolt from the capacitor?
How much drag would it take to overcome the initial weak torque, I wonder? I am going to disengage the drive pulley to the roller gears and see if that makes a difference. I could also disengage the main pulley and see if the motor starts whilst in the machine under no load at all.
In many cases, it's a combination of factors that add up to a problem. Perhaps this is the case here? A weak capacitor, a bit of extra drag from a worn roller-gear bearing and Bob's your uncle!
More experimentation and then the call to the Scheppach agent, I think. They do have a good service, I'm told - but it will no doubt cost me.
Lataxe
The reason for the starting switch and capacitor is that a single-phase motor doesn't know which way to turn when you first apply power. It needs an initial kick in one direction or the other. The capacitor modifies the phase of one of the windings just enough to give that kick.
Once it's turning, the momentum keeps it going in the same direction.
-Steve
Steve,
Having reviewed all the info I can get and talked to Philip, I think the problem may well be the capacitor. When the drive belt is pulled the wrong way after the "switch-on & hum", the block will turn backwards! This is surely a sign that the capacitor is not delivering sufficient "jolt" as you describe.
Also, when the drive belt is disconnected, the motor will start and turn as normal - so even the slight drag of the knife block et al is enough to prevent rotation begining. That capacitor it clagged up hard on to the motor housing, so it gets hot. After 10 years, that heat and the natural tendency for capacitors to deteriorate over time, may well be the issue.
I am off to see how much a new spare costs and whether it can be fitted by me or requires an electrician. The part is not separately named in the manual's exploded diagram, although there are screws to dismount it....
Thanks for the help.
Lataxe
Have you had any luck in your quest?
R,
Just 30 minutes ago the new capacitor dropped through the letter box. I ordered one from the UK Scheppach agent, who was very helpful but the new electrical thang still cost me £47.30 ($95)!
I will fit it later and hope it's the answer. I dismounted the old one, after the agent told me it was the likely cause (as Philip advised) but also that I could do so safely, despite the dire warnings in the manual not to take them screws out the cover, let alone gaze upon the electrical internals. The old capacitor is a sorry sight, with cracks, bulges and even an exuded bleb.
In an hour I'm off to the shed to reassemble the machine and to do some woodworking. I'll report later on whether the capacitor has fixed the problem.
Incidentally, I asked the Scheppach agent what second-hand versions of my machine sold for. In good condition they go for between £400 and £500! SInce I only paid £650 some ten years ago, I am tempted to sell and upgrade. Scheppach's new version of the machine I have costs £800 but includes a "free" dust collector of normal retail cost £100. More to the point, it has a slightly upgraded motor, a better-designed fence and an extra 50 Kg courtesy of larger cast iron tables. I am tempted.
Lataxe, amateur electrician.
Edited 2/16/2008 5:22 am ET by Lataxe
Lataxe,
I'm glad you are on the right track. However, I see you have neglected one important step in renewing your motor capacitor.
Before energizing the capacitor for the first time you would do well to put a bone in your nose and dance around a fire for a few minutes chanting "ohm, ohm, ohm."
This will appease the electrical god, (or as I used to call him at school, Prof. Shattack).
Failure to include this step may cause your Billivester relay to slip a pole resulting in a knackered framastan gear and a sheared kirby pin.
Good Luck!!!
Oh happy day! The new capacitor has fixed the problem and all now starts & runs sweetly. Since I've had the machine in bits, it also got a thorough clean & lubricate/grease of the parts, so is humming well.
Attached are pics of the old and new capacitor. If that old one had not been hidden away in the plastic electrickery box, I might have seen it's deterioration earlier. It's remarkable that it's kept working until it did.
I'm tempted to drill that plastic box for the capacitor's wire, find a round waste pipe clip and attach the new capacitor to the outside of the motor plate somewhere. Surely it would be better away from the heat of the motor and visible to my inspections? For now, its in that plastic box.......
Lataxe
Good job!!
From the price of that little goody I was expecting a gold color though!
Lataxe-That's the worst case of capacitor abuse I've ever seen. You must mend your ways before the neighbors start talking.Don
Bravo! Undoubtedly Sheppach and agent have charged you with their retirement pension included in the price of that standard electrickery item, but you saved on not having a Qualified Electrocutor of the Realm attend with one insulated screw driver and side nippers.Philip Marcou
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