Introduction and plead for help. Combination machine woes..

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Rustic_kernow

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Good evening,
My name is Nathan, I'm based in Cornwall and I've just taken on a new workshop making simple furniture, still a novice when it comes to woodworking and joinery.

I found this forum whilst trying to google answers to my problem so I thought I would put a post up in the hope someone more knowledgeable will be able to shed some light on the issue. Basically I have a combination machine that keeps burning out contactors so that the machine only runs when holding down the trip switch on the contactor itself, but the switch doesn't reset. I have already replaced it but it happened again very shortly after.

It's a single phase 240v Rojek KPS310a with 3 motors running a planer/thicknesser saw and spindle moulder. I've ruled out stop switch problems and safety switches. It's on it's own 16amp plug and circuit but since moving into the new workshop all the motors have been very slow to start up and sometimes require a pull or nudge to get going. Almost as if it's not drawing enough for the motors to initially start. Eventually this causes the contactor to burn itself out and stop working. I had no issues in my old workshop and the fact that all motors act in exactly the same way would suggest the problem is not with them.

As you can probably tell I'm fairly clueless but if anyone has experienced anything similar or can help it would be greatly appreciated.

Thanks,
Nathan
 

deema

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There is something seriously wrong, if you continue you are likely to burn out the motors / start a fire and or get an electric shock. Get an industrial electrician to have a look. The starter for instance should have a current sensing relay as well as a main contactor, this should trip when full current is pulled for more than a very short time. Your machine does not appear to have this for some reason.

It sounds like a bad connection, wire too thin, or some resistance causing too much inertia for the motors to over come. What ever ut it is do not use it / try to push blades around to start it until it’s been properly sorted out.
 

baldkev

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Hi nathan,
Being as you are new, you wont already know, but Deema rebuilds machines ( in great detail and depth ) so his advice is the best option.

I cant add anything helpful as i dont do much with electrickery

Welcome to the forum
 

nickds1

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Just a random thought.

We're in a rural location and we saw some odd behaviour when bigger machinery was powered up.

Turned out that our power quality wasn't great - nominally we have 100A 3phase but with only a 36A load the utility voltage was dropping from 240 to 210.

A long and tedious "discussion" ensued with UK Power (who are the infrastructure provider) and that culminated with them replacing the local substation.

They still have to replace the actual feed to our property - the cable dates from the 50s or 60s, is about 150m long and is probably underrated.

UK Power were pretty easy to deal with and once we had identified the issue they came in with a whole bunch of monitoring equipment to isolate the issue.

Big kit is all a lot happier now however we still get brown-outs etc. so all IT equipment is on good quality online UPSs.
 

baldkev

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Thats interesting. ☝

Nathan, do you have any other machines with a big motor? A combi probably has 3 motors of 2.2kw? So you need something with a motor the same size or bigger to test the incoming feed
 

nickds1

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I should qualify that slightly - the utility voltage was measured at the meter cupboard main fuses so as to eliminate any losses due to the cabling within the property.

I am an electronic engineer by training so have a fair bit of good quality test equipment myself. Once we suspected the utility feed (incandescent lamps were visibly dimming when certain equipment was powered up) I left a recording meter on the utility feed and turned stuff on and off. I also had a three phase current clamp on the utility supply.

We also measured the power loss in the cabling within the grounds in order to show that this was a utility provider rather than our issue.

I should also mention that management of three phase is a subtle art as it's quick to anger. Single phase is far simpler - not so many harmonics or load balancing issues (still get harmonics though)

This all may or may not be relevant to your issue, but it's something that's often overlooked.
 
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Rustic_kernow

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Thanks everyone for your quick replies, I should say I haven't excessively been using the machine since I've been having issues. I have had two electricians to look at the machine now, they found issues with one of the safety switches and an external stop switch as well as the contactor which they advised I replaced which I have done, although the machine remained slow to start up (as has always been the case) It worked fine for a few days until it went again yesterday. I'm sure it does have a current sensing relay which has a reset button and a dial this is connected to the main contactor but it doesn't 'trip'. Or at least the reset does nothing to help. Could this be the cause of the problem? Image attached if it helps.

I have suspicions it may be related to the incoming power to the machine/workshop, it's a rural farm with a few commercial units some of which use much larger machines than mine. But mine is the furthest away and was only recently converted from an old chicken shed.
 

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guineafowl21

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Sounds like a voltage drop problem, possibly due to undersized conductors or a poor connection somewhere. I’d get that checked soonish as where there’s voltage drop, there’s heat, and also it will do your motors and switchgear no good at all.
 

baldkev

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I had one of those boxes go on an elu planer i had. I got lucky and found one on ebay, new. Wasnt cheap though..... but it was the only one i could find with the exact code number.
The symptoms of mine were it just stopped working on the main switch, but when you press down on the little black button on that box it would fire up.
 

Spectric

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Deema's suggestion of getting an industrial electrician is the way to go, there is something wrong and it may be the actual electrical instalation in the workshop at fault and not the machine. As you say you have just taken on this workshop so having the electrical system given a once over will not do any harm, but avoid using a domestic installer, they are not what you want when machinery is involved.
 

chris.s

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when working on air conditioning I have found that with single phase motors that are slow to start that it has been the motor capacitor that needs replacing your motors are more powerful than I was working on and looking at the machine specs it uses 2.2kw motors and I don't know how these machines run but if all 3 motors are running and starting together you will be overloading a 16A supply.
Also £87 for a motor capacitor is a rip off if you need them shop around should be £10-20
 

baldkev

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I don't know how these machines run but if all 3 motors are running and starting together you will be overloading a 16A supply.
Usually you select a funtion on a rotary knob and the relevant motor fires on the start button.

The capacitors can cause slow starting / needing a bump. This is usually accompanied with a noticable hum
 

Dave T

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I would check the tightness of the connections within the power distribution system, but starting with the 16A plug and socket nearest the machine. Make sure the power is isolated first! If you take out each wire and inspect it before tightening it back up, you may find one that is slightly blackened which is a good indicator of the source of a voltage drop problem.
If it was only one of the motors, then the capacitor would be a good place to start, but it is unlikely that all three motors would fail together.

the other option is to run the machine whilst point a laser temperature gauge at each connector within the machine and in the distribution system before the machine. Somewhere, possibly not in your workshop, there may be loose or broken connector which will get hotter under load.

good luck

Dave
 
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