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Bob? Help?!

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Bob? Help?!

Postby SamQ aka Ah! Q! » 23 Mar 2016, 15:24

I have just finished restoring a Wadkin 10" AGS and I 've installed an Axminster sale /bargain electric motor (2200W, 11.6A, class B ). The feed to my shed is 2x2.5mm live/earth/neutral, terminating in an old distribution board, on 30A fuses, yes, fuses, but is connected to the house dist. bd. which has RCD's. I presume they're 30A for the ring power circuit I .

The motor is connected directly into the bus bars/30A fuse of the shed box via a 16A dark blue ("Arctic"??) cable and a brand new DOL starter. It has a new pulley and a VERY tight pair of belts leading to the saw arbour.

Here's my problem: when I tested the motor - briefly, 10 seconds? - on a 13A plug, clattering and banging, followed by normal running, then she blew the fuse in the plug, but nothing tripped. When I connected via a BLUE commando plug/socket (like caravan parks?) and placed the DOL in-line, the motor starts, runs for 10-15 seconds, then stops. Unplug, hit reset on DOL, re-plug after a couple of mins, starts, runs for 10 seconds, stops.....unplug, reset, re-plug, starts, stops 10 seconds later......sheesh :( . I do notice a fair bit of vibration in the belts too.

It doesn't trip anything, nor does it blow the fuses.

ALL THIS UNDER NO LOAD - JUST THE BELTS LEADING TO THE ARBOUR.

Bob, does this sound like a run capacitor bandjaxed and needing replacement? Or....?


EDIT: Just had a brainwave...took the belts off and the motor clatters into action, runs beautifully and for a long time, admitttedly with slight slow rhythmic oscillation noise... put ONE belt on and we are back to square one....Is this a case of belts-tighter-than-a-duck's-b*m is causing motor bearings to overheat d'y'reckon?


Yours, hopefully, Sam
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Re: Bob? Help?!

Postby kirkpoore1 » 23 Mar 2016, 17:39

I'm not Bob, but it sounds like your motor may be drawing more amps than your plug is rated for, causing it to trip. I'm wondering whether you've got a wiring issue that is limiting the number of amps that you can draw and keeping your motor from coming up to speed with even a minor load, or perhaps a low voltage condition. Do you have a voltmeter or an ammeter? If so, can you take some measurements at the motor?

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Re: Bob? Help?!

Postby RogerS » 23 Mar 2016, 19:01

Do you mean 'plug', Kirk ?

SamQ - you don't say how long your cable run is. I reckon Kirk is on the money and that you've either got too long a cable or you have a high-resistance connection somewhere - maybe those manky old 30A fuses and fuse holders ;) . As Kirk says, stick a voltmeter on the feed to your motor and see what it drops down to when you fire it up.

I'm lucky where my workshop is in that I'm fed from a transformer directly off the 11kv line. My nominal voltage is 250v but when I fire up my Sedgwick which is alleged to draw an 80A spike on startup, and as my workshop is fed with a too tiny cable, the volts still only drop to 230v at switch-on but swiftly rise back up as the motor gets up to speed and stops drawing that large current.
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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 23 Mar 2016, 19:19

Thanks Roger and Kirk, my cable run is about 30 metres and remember, the cable run is a double. Some time ago, I ran the figures through an on-line voltage drop calculator and it quoted a loss under 10 volts. Does anybody know if that little(?) a drop matters in a motor of 2200W/11.6A? I can run a similar power planer and its 750w dust extraction without the slightest problem, even when thicknessing old oak.

Puzzled, Sam
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Re: Bob? Help?!

Postby kirkpoore1 » 23 Mar 2016, 20:00

Sam:

I'm not sure what you mean by "the cable run is a double". Of course, that could be because I'm not up on the local lingo.:) 30 meters is a long run if your wires are marginally sized.

Edit: I did a little googling and I _think_ 2.5mm wire is rated for 20 amps, so that is likely OK. You're still going to have some voltage drop over that distance, and if you have some extra resistance from old fuses, who knows?

Your overly tight belts could be contributing to the problem. They would exacerbate the starting surge of amps that your motor is pulling. However, given that your overload still trips after 15 seconds even while not cutting, I'm confident that isn't the whole story. I think even if you got some looser belts, you would trip your overloads while cutting. I really think there is a possible connection issue going on, and that measurements will be your friend rather than simply a random guessing issue.

Good luck with it, though, and keep trying. You'll get it worked out.

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Re: Bob? Help?!

Postby 9fingers » 23 Mar 2016, 21:49

Sam,

A couple of things
1 A tight belt is nothing to be proud of or to aspire to. It will lead to premature bearing failure. 1/2" slack on the longest run is about right.

I don't think you mean RCD tripping but instead I think you have MCBs and I'd bet 1/2 pint that they are type B
You need type C especially with such a long cable run. The latter is causing a slow start up of the motor and then the type is intolerant of the long duration starting surge. I'd be tempted to try a C40 in the consumer unit in the house.

Bob
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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 23 Mar 2016, 23:12

Thanks Bob and Kirk, that's really informative and makes a load of sense. Seems slacker belts and a bit of metering is in order. I'll get on to it, probably in about a week's time, as La Famille arrive in numbers tomorrow and I'm delivering an intensive 4-day course immediately after Easter. I have a number of projects that really need the AGS to be fit'n'well, like the wedding presents PLURAL for late May... :oops:

This one is not going to be allowed to slip. More when I have information to share.

Thank you again, Sam
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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 12 Apr 2016, 22:10

Hi Folks, I've been busy, so apologies for a late reply. I've also done some measuring etc and here are my findings:

Image

1. My Consumer unit is about 25 years old, fitted with two main 'trips', the L.H. one protects circuit 5 (32A, type 2 individual rating). This serves the ring circuit to kitchen, utility and shed. While I am working, it provides power to a fridge, a freezer and a couple of low wattage lights. IT HAS NEVER TRIPPED.

2. My power supply to the shed is 31 metres/95 ' of 2 of 2.5mm multistrand cable (six stands in all, 2 Live, 2 return, 2 earth), initiating in a pair of junction boxes in the utility room. I put all the figures into TLC's voltage drop calculator - and others - and 2.5mm seemed fine(??). My multimeter gives a reading of 238 volts here.

Image

3. The multistrand terminates in an old MEM distribution board I had, the two live starnds are fixed to the live bus bar, the return to the neutral bus bar and the earth.. etc. This antique has fuses(!) and I run the 16A dedicated radial circuit off the 30A fuse two in from the left.

Image

The trip on this biscuit tin is as above. NEITHER THE TRIP HERE, NOR THE FUSES ATTACHED TO IT HAVE EVER BLOWN.

Without load, this unit reads 236 Volts, in use, with a 2.2Kw P/Thicknesser, it reads 224 Volts.

Image

4. The motor that started this thread off is connected to a D.O.L. starter, brand new. It is an Axminster aluminium T.E.F.C. 2.2kW jobbie (a reasonable copy I think of an ALPAK original).

Now, it starts with no load, admittedly reluctantly, sounding like a bunch of spanners in a tumble dryer for maybe two seconds, then runs smoothly for as long as you like. Put the thing into my AGS and try to start it, I get maybe 7-10 seconds use, then it cuts out. If I take the tension off the belts slightly, the bunch of spanners are back.

I took it off, tested the two capacitors separately, off the terminal block of the motor and I did not get a gradual growing resistance, it simply went straight to infinity for both.

I then put an old ALPAC motor into the AGS; same physical configuration as the Axi, but 1.1kW, cuts all day.

I have a 2.2kW P/T an old Elecktra Beckum; it, plus a 1.1kW extractor run happily off the same electrical supply......with four six-foot fluorescent tubes on too, but on a separate fuseway on the MEM.


Any ideas Folks?

Sam
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Re: Bob? Help?!

Postby Robert » 12 Apr 2016, 22:42

I'm no expert (bob will be along soon no doubt) but having a start capacitor must mean there is a centrifugal switch to disconnect it once the motor has got going. from what you are describing it sounds like that switch or maybe the big capacitor isn't working properly.

more here - https://en.wikipedia.org/wiki/Motor_capacitor
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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 12 Apr 2016, 22:48

Thanks Robert. I was having a growing suspicion about the switch not disengaging. The fact that the motor starts and runs, off load, suggests the caps themselves are OK? Mind you, that jump to high resistance is confusing.

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Re: Bob? Help?!

Postby Robert » 12 Apr 2016, 23:02

A capacitor will have a low resistance when tested with a multimeter for a second then go to open circuit as far as a DC tester is concerned.

capacitors kind of store voltage. how much power at that voltage is the 35 uF or 200uF number (uF = micro Farad) so when your meter applies say 9V to resistance test the capacitor takes power until it is charged up to 9V. Once its there it doesn't draw any more so seems open circuit to the meter.

All different on AC of course.

A capacitor holding on to 240V mains after the thing is switched off is dangerous so there is usually a small resistor inside to discharge the voltage over a few seconds. hence it will repeat the performance when you test it again.

As a trainee I can remember removing said resistor and using a capacitor to explode flies. A charged capacitor in the wrong hands is a dangerous thing. It's a wonder I never got a Darwin award as DC voltage is very dangerous.
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Re: Bob? Help?!

Postby RogerS » 13 Apr 2016, 05:22

Sam

Have you done this ...mentioned in an earlier post way back.

As Kirk says, stick a voltmeter on the feed to your motor and see what it drops down to when you fire it up.
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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 13 Apr 2016, 07:46

OK Roger, here's what I did. The capacitors I discharged with an old inspection lamp, to make sure neither held charge before I undid the screw terminals connecting them.

I was writing what I did next, but doubt has crept in, so I'll repeat and annotate tonight after work.

I did manage to record a voltage on the dicky 2.2kW motor. Supply was 236V, motor running (badly and noisily) just on belts, not cutting, was 214V. When I put the physically identical 1.1kW motor into circuit and ran it, I got 236V supply, 224-228V running, nearly same as for the heavier Planer Thicknesser above.

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Re: Bob? Help?!

Postby 9fingers » 13 Apr 2016, 09:58

At first sight, this looks like a case of a totally inadequate supply to the point of use but I'll wait for confirmation of these voltages.

A more precise technical description of noises rather than " it sounded like a bag of spanners" would be useful! :lol:

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Re: Bob? Help?!

Postby RogerS » 13 Apr 2016, 10:23

Exactly my thoughts, Bob.

Sam...when you start your motor, there is an initial huge draw of current and this will cause a voltage drop because of the resistance in your cable feeding the workshop/motor. It is a very short spike (usually) and the drop in voltage can be difficult to pick up especially if you are using a needle type multimeter as there is the inertia in the needle to respond in time to give you an accurate reading before that initial current surge stops - as the motor comes up to speed.

Normally if the cable has low resistance - in other words is properly sized for the job in hand - then this voltage drop will be negligible and the motor will come up to speed quickly, the starting current drawn will reduce quickly and everything will be tickety-boo.

But if I understand you correctly - although I find this sentence a little confusing - Supply was 236V, motor running (badly and noisily) just on belts, not cutting, was 214V. then at 214v, the motor will take much much longer (if it starts at all and even longer once you start putting a load on it such as belts and cutter heads etc) and the current draw will remain high for a much longer period....which will then cause a breaker to drop out or worse still, cause your motor to overheat and burn out.

So the critical measurement to take is the voltage at the motor at a fraction of a second after THE moment you hit the ON button. It's probably worth temporarily connecting a couple of wire tails from the motor to your multimeter using using chocolate blocks or some such if you're finding it difficult to hold the probes on and start the motor. I have a plug-in power meter that has a 13 amp plug on it and that shows me voltage, current drawn and a whole host of other things and I sometimes find it useful to have it plugged in to a 13 A socket adjacent to what machine I'm working on and I can see the voltage as I turn the machine on.

I'm lucky - sometimes my nominal voltage in the workshop is 252v and that drops down to 238v when I turn on my Sedgwick MB. 238v is more than enough to ensure it spins up quickly. But having said that, my cable run is a measly 4mm and not that long a run from the house and so in winter I will usually make sure I switch off any heaters etc ...simply to make sure that the voltage at the motor is as high as possible for starting.

It could also be a high resistance connection anywhere down your supply line, breakers, fuse boxes, contactors etc. That's another possibility.
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Re: Bob? Help?!

Postby Robert » 13 Apr 2016, 10:28

Thinking about it... if you can remove the motor why not take it into the house and plug it in to a 13a socket? It might take out a 13a plug fuse but it might not and would prove if the supply is the problem.
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Re: Bob? Help?!

Postby 9fingers » 13 Apr 2016, 10:53

I suspect this will turn out to be an illustration of a degree of perversity of electrical installation

At present there is a type b breaker in the house and the high resistance of the wires to the shed mean that the current is limited so the breaker does not trip but neither does the motor run properly.
Fixing the cable voltage drop should sort out the motor issue but the breaker will likely trip due to the starting current. The average DIYer will be upset that changing the cable has not totally fixed the problem !

I strongly suspect that a type C breaker in the house will also be needed.

Way back in the continuing saga of Sam's saw, the possibility of a three phase inverter was mooted - ISTR that the saw might have had a 3 phase motor or that a saw with a 3 phase motor was being considered.
Because inverters manage the inrush currents needed to start motors, they have much greater tolerance to higher resistance supplies.


As a complete aside, I have an internet friend who buys, sell and demonstrates WW2 air raid sirens to enthusiasts. ( we call them by the initials of Air Raid Siren Enthusiasts!! :lol: )
These sirens have 5hp (3.7kW) motors and by careful programming and a few mods inside the inverters, I supply these inverters to his customers who can then run them from a 13amp plug with a standard 13amp fuse in. It all relies on sneaking up the current slowly so the 13a fuse does not get any thermal shocks. It also possibly helps that at ground level the sirens are so f'in loud that you don't run them for very long!
Very versatile things these inverters!

Bob
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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 13 Apr 2016, 11:54

Thank you Roger and Bob, your time in answering much appreciated.

The noise? It sounds like a metal wotsit banging off a second metal wotsit many times a second, but not rhythmically, very randomly.

Bob, until very recently, I was operating on a small budget and the cost of a 3 phase control box for 3hp motors was beyond me. (The AGS came without its motor, though documentation in my possession suggests it originally was 3ph). I took advantage of an AXI offer to get a single phase one, the one this post is all about.

I understand that yourself and Roger are both saying my supply isn't up to it and I need to upgrade to 4mm or 6mm cable. Now that my three kids have graduated and got jobs, the Bank of Dad may finally post a surplus with year-end accounts. That will mean new cables at least and possibly one of Bob's enhanced inverters.

I think this thread has run its course. Thanks again everybody.

Sam
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Re: Bob? Help?!

Postby RogerS » 13 Apr 2016, 13:27

Hi Sam


Not necessarily so because going back to your OP you say you have two 2.5mm cables and IIRC your run is not that long. And the resistance of those two cables is less then a 4mm cable which makes me wonder about a bad connection somewhere ..loose screw etc
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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 13 Apr 2016, 13:39

Oh. Thank you Roger.

The cable run is about 32-35 metres, and various voltage drop calculators seemed to indicate 'fine'. Others, with more knowledge than I have, may blow a hole in that optimism.

What has puzzled me all along is that the P/T has a near-identical-sized/shaped motor, with look-alike twin capacitors, and an identical power rating, 2.2kW. I run it and a dust extractor, no problem, but the minute I try its counterpart, the Axi motor, I get problems. Eh??

What I have resolved to do is take it to my local motor rewind place and get it tested. I think yourself, Bob and Kirk have been more than good with time and thought, but the time has come to stop being mingy with cash and see if a 'pony' will get me a diagnosis from someone who can see, touch and test the thing.

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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 13 Apr 2016, 14:03

The other thing I am going to try is measuring the amperage to, and voltage across, my working machines - I'm not sure my generic, canary yellow multimeter is too accurate or versatile enough. I have an electrician friend who owes me a favour. :|



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Re: Bob? Help?!

Postby kirkpoore1 » 13 Apr 2016, 14:48

SamQ aka Ah! Q! wrote:The other thing I am going to try is measuring the amperage to, and voltage across, my working machines - I'm not sure my generic, canary yellow multimeter is too accurate or versatile enough. I have an electrician friend who owes me a favour. :|



Sam


Favors are good. Experts are good. Let us know what he says.

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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 04 May 2016, 19:02

Hello again. I have finally got everything sorted. Two resolutions:

1. The centrifugal switch on the motor is sticking badly. My motor rewind bloke put it on his nice clean supply with a beautiful heavy duty current meter and the amperage went off the scale and stayed there, while the motor made a braying sound....two-three seconds only, but the needle stayed hard up against the limiting pin at the extreme end of the scale. It dropped back to a few amps when the switch let go, so I left the motor with him for a strip-down and touch up. He also said his experience of these aluminium bodied motors was that the switches in them were 'pansy excrement'...but then, his normal daily motor repairs involve armatures that can only be lifted by forklift...

2. The shed wiring was laughed at by my tame Sparks. He measured voltages and made a quick and dirty calculation of possible amps/temperature rise with the sticking switch and then gave me 'that look' :eusa-naughty: . I was instructed to "not faff around any more with the piece of wet 2.5mm string" I was using and he put me on the trail of some excellent 10mm squared cable. I got two almost complete 50m rolls for £30. Chuffed.

I anticipate not being able to start the electrical work until early June, as it involves a long run of buried cable and I have imminent commitments in the shape of a family wedding 'across the water'.

I have worked two jobs for years to make my family finances work, that's - in part - why my restoration projects take so long. In mid-June, I will be able to step aside from my second paying job, and also, for the first time in several years, I will not have an expedition or major construction project to complete over the summer. The AGS restoration saga will therefore accelerate and come to an end. I REALLY look forward to finally being able to work wood instead of 'firefighting' various problems.

My grateful thanks to everyone who contributed to this thread.

Sam
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Re: Bob? Help?!

Postby SamQ aka Ah! Q! » 10 Jul 2016, 10:48

Sorry this thread has stalled. My wife, of thirty years, is shortly going in to have a large tumour removed. My prioroties have shifted a bit....

Sam
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Re: Bob? Help?!

Postby 9fingers » 10 Jul 2016, 10:51

SamQ aka Ah! Q! wrote:Sorry this thread has stalled. My wife, of thirty years, is shortly going in to have a large tumour removed. My prioroties have shifted a bit....

Sam



I have too many friends going though similar things at the moment.

Best Wishes to you and yours Sam!

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