Looking for some help....Motor woes

[OldWood]

Roy
I tend to agree with your opt out. I now see my working career as something like my school one - something I want to forget.

By the way I want to challenge your subscript - "Growing old is obligatory" - true physically, mentally we are all trying to remain young, but the 'wise' part is hardly an option as that would mean that we could opt-in or opt-out of being wise which is not realistic. I would suggest that "growing wise is subjective" as we cannot define ourselves as being wise, it cannot be measured and it can only be observed by others.

Philosophical discussion to follow !

Rob

 

[Digit]

Oh I don't want to forget it Rob, some of it was absolutely hilarious!
But I could take over a section on that sort of subject.
Imagine, I once had the office girls lined up whilst an Arab customer looked at each in turn till he found one he thought was the same size as his Fiance. I then asked the girl her dress size and ended up carting him around the city boutiques whilst he selected a number of outfits.
Just another day in the life of your average exec!

Roy.

 

[OldWood]

Office girls - either you are *very* old, Roy, or you worked in a different part of the electronics industry from me. All the members of the female species I came across were software programmers and would have taken considerable offence I suspect if lined up like that.

Rob

 

[Digit]

That was electric motors and pumps Rob. The Arabs tended to send either a highly qualified engineer to discuss their requirements or the Sheik's favorite son. And I got em all!

Roy.

 

[GraemeD]

Unfortunately I didn't get a chance to try this out today....so it will have to be next weekend now, as I'm back at work tomorrow. I will report back on the outcome........

Graeme

 

[GraemeD]

Gentlemen,

I have a little additional information after getting the chance today to try the experiment we discussed. I essentially bypassed the inbuilt start cap switch with a manual one, which I could control as I turned on the motor. Had a false start where the first switch I tried managed to spot weld itself closed (I thought it was sufficiently rated....clearly not!). The next one (an old 10A plate light switch) did the trick nicely.

And the outcome....well, you were right, it seems the motor hasn't hit its synch speed before the inbuilt start cap switch drops out. If I give it about three seconds then switch out the big cap, the planer runs fine. So, it seems the inbuilt two second timer is just a little short for the load I am using.

Tomorrow's job is to install the planer knives and see how it behaves under load once started. If it works fine, and planes timber without struggling, I can consider adding some kind of external start cap timer switch to ensure it starts every time. Job done.

If however it proves to be underpowered....as it may do....then I'm probably better getting a 1.5HP motor instead. I'm guessing a 1.5HP motor will not have the start up problem, having a bit more torque available to it. Shame not to be able to use my nice new ABB though if this were the case!

Funny really....I naively thought that a 1HP would be fine to run up the planer, and maybe it would be a bit short of power, limiting the depth of cut. I had no idea that it may not even manage to spin up he knives! Not a lack of power as such, but a by-product of it being a lower power than ideal.

I should have more feedback tomorrow after the knives have been installed and the machine tested. I feel like I'm making progress though!

Graeme

 

[Digit]

Logic says that a 1.5 HP motor would spin up faster under the same load, but as regards the smaller motor, if it performs as you wish once upto speed an external timer should solve your problem.
Variable timers attached to a contactor are common place in industry for just this type of problem, or at least they were before I retired!

Roy.

 

[OldWood]

Graeme
Many thanks for your feedback. I'm not sure if I got to the correct diagnosis first but it's nice for once to be able to assist in helping someone else with a problem.

I hope Bob Minchin (9fingers) is watching this thread as well as the problem you have met will certainly not be unique and perhaps he needs to add a note about it in his induction motor FAQ.

Rob

 

[GraemeD]

I think the problem here is actually because the start cap switch is electronic and has the two second cap applied to it. If it was an old fashioned centrifugal switch, it would automatically hold on for longer, until a higher speed was reached.....unless those switches are not accurate enough to achieve a stable running speed?

Either way, I suppose holding the start cap in circuit for longer will be stressing the windings more, but then if it works, and is ok for the long term, it is definitely an option.....depending on if the motor is fundamentally up to the job once it's running.

I should know more later today after some tests!

Graeme

 

[9fingers]

I agree Graeme,

As you say a centrifugal switch would possibly hang on for a bit longer and should even the motor not start properly, the overload trip in the NVR starter would protect it.

In the electronic version, the protection of the starter winding is given by the 2 second timeout allowing the maker to be even meaner with the amount of copper in the start winding. Then if as in your case the motor does not reach synchronous speed for whatever reason, the overload trip in the NVR should protect the run winding.

You said earlier that your motor started smoking/smelling. I would have expected the NVR to have been tripped before it got to that state.

I can't help wondering if you even have and NVR with overload protection fitted or maybe it is set to trip at too high a current.

Rob, I am indeed following this thread with interest but honestly wonder what constructive advice I will be able to add to my FAQ to help others avoid this situation.

Bob

 

[Digit]

Do they still fit contactors with adjustable timers Bob? If so, subject to the start winding, one of those plus an overload should sort it.

Roy.

 

[9fingers]

Do they still fit contactors with adjustable timers Bob? If so, subject to the start winding, one of those plus an overload should sort it.

Roy.

Roy,
I've only seen these on star/delta starters for higher power 3 phase motors.
It is possible that a starter switch built on a modular system could be configured with a 240volt coil, a low power overload trip and a timer from a start delta starter but this would be an expensive route with new parts.

Going way back, manual starters would have a biassed toggle switch which was held down against a strong spring during starting and released when the motor got up to speed. I passed the last one of these I had to a collector of old motors a couple of years back

If I were faced with the OP's problem on my own machine I think I'd use
a timer relay externally in place of the electronic module or approach ABB to see if they have a solution. However I would be reluctant to write this up a solution in my FAQ as too long a starting period would likely pop the starter winding and in turn damage my credibility!

Bob

 

[Digit]

Going way back, manual starters would have a biassed toggle switch which was held down against a strong spring during starting and released when the motor got up to speed. I passed the last one of these I had to a collector of old motors a couple of years back

Yeah I remember them! And even earlier devices!
A timer come relay is effectively a contactor plus timer so basically what I had in mind. Depends on Graeme's tests once the machine is running of course.
I was lucky, I bought a six inch planer with a 3/4 HP 3 phase motor and two days later picked up a 21/2 HP motor with a duff capacitor from the local tip!
How lucky is that? :lol:

Roy.

 

[9fingers]

Going way back, manual starters would have a biassed toggle switch which was held down against a strong spring during starting and released when the motor got up to speed. I passed the last one of these I had to a collector of old motors a couple of years back

Yeah I remember them! And even earlier devices!
A timer come relay is effectively a contactor plus timer so basically what I had in mind. Depends on Graeme's tests once the machine is running of course.
I was lucky, I bought a six inch planer with a 3/4 HP 3 phase motor and two days later picked up a 21/2 HP motor with a duff capacitor from the local tip!
How lucky is that? :lol:

Roy.

Luckier than I have been for quite sometime!!
Although I have just picked up a morticer today with X Y table off the bay.
I just need to build up my strength and get it out of the car now.
So I think maybe my luck has changed for the better today.

Bob

 

[Digit]

I wish you luck Bob, I just don't get on with mortisers, I find there is too much hand fitting to follow. Over the years I've graduated to morticing with a router and jig, and the tenons I cut on my TS, again with a jig.
The most fitting that I do is rounding the ends of the tenons with a rasp.

Roy.

 

[OldWood]

However I would be reluctant to write this up a solution in my FAQ as too long a starting period would likely pop the starter winding and in turn damage my credibility!

Bob

Thanks for that point, Bob - it's not one that I'd thought of. I do suspect that you have a cynical outlook on manufacturers :roll: :twisted: , but of course that is fully justified...... and 'credibility' is what they don't necessarily have.

Rob

 

[Digit]

Actually Rob, re-reading Graeme's OP it looks as though it was the run circuit that over heated due to the machine not being upto speed. Whether it has been damaged or not though only time will tell.

Roy.

 

[9fingers]

However I would be reluctant to write this up a solution in my FAQ as too long a starting period would likely pop the starter winding and in turn damage my credibility!

Bob

Thanks for that point, Bob - it's not one that I'd thought of. I do suspect that you have a cynical outlook on manufacturers :roll: :twisted: , but of course that is fully justified...... and 'credibility' is what they don't necessarily have.

Rob

Whether or not it is cynical maybe debatable. However in manufacturing minimising the works cost price whilst maintaining technical reputation is the name of the game.

I have watch motor evolution with interest.
The starter winding has to provide sufficient magnetic phase shift to start the motor running with its rated starting load torque applied.
A long time ago starters had no capacitors as suitable values were expensive and unreliable at mains voltage. The windings used almost as much copper as the run winding.
Then AC electrolytics came available in modest values but still quite expensive but they enabled less copper to be used.
The the last 25 years or so, high reliability, high value polyester capacitors have become cheap and so modern motors use electrically large capacitors and even less copper in the start winding.

In the last decade (say) integrated power electronic modules have become much cheaper and so now manufacturers can prune yet a little more copper out of the design by employing the electronics to switch off the starting current just before the smoke comes out. Additionally the reliability of the motor increases as the mechanical switch has been done away with.

This all makes sense when you look at the price of copper which has gone through the roof along with most raw materials often due to third world producers wanting (and deserving!) a higher standard of living and the voracious appetite of China and India for raw materials to flood the west with cheap goods for us to spend our borrowed money on!

Yeah OK I'm cynical then :lol: :lol:

Bob

 

[GraemeD]

Interesting conversation in my absence! Anyway, I had a good play with the planer this afternoon. Quite a landmark actually, as this was the first time I have ever had it up and running! It's been sitting in restored pieces for a couple of years waiting for me to conjure up the courage to complete it. (For some pics if you're interested, take a look at a previous thread, https://www.ukworkshop.co.uk/forums/wadk ... 77-45.html, from about halfway down the page).

Anyway, I set up the new knives (which was a challenge in itself as they are set at a skew angle, rather than parallel to the cutter block), and went through the start up sequence. It cut wonderfully. I ramped up to a full width piece of oak, and managed a 1.5mm deep cut with no perceivable effect on cutter speed. The motor was warm at the end of the test, having run for maybe ten minutes, but no warmer than any other machine I have. I reckon my 1HP motor is therefore man enough for the job. All we need is to get it started!

I mentioned previously that the original fit motor by Wadkin would have been a 1HP, and the lower than expected rating may be partly due to the skewed knives needing less power. Just a thought.

To answer your question, Bob, I was a bit naughty and ran the motor first time with no NVR/overload protection. I had my reasons but maybe it was a bit foolhardy. However, the motor wiring box was open at the time I span it up, and so I saw/smelt the smoke pretty quickly and was able to switch off. It wasn't bad, more hot varnish vapour from the internals rather than billows of black smoke, and so far I can see no ill effects....though whether issues will occur in the future, I have no idea. We'll see.

Anyway, my next port of call is to contact ABB and see if they have any way to change the time out. I expect not, but worth asking before going with the external timed relay.

So, many many thanks for all your help and support, guys. I now understand where I'm going with this, and how to make it work. Definitely wasn't obvious to me at the start....I was truly convinced I had a duff motor!

Graeme

 

[GraemeD]

Been communicating with ABB today....very helpful, but looks like no dice. There is no way to change the 2 second timeout....I suppose I guessed that may be the case. I also asked about increasing the value of the starting cap (an Idea I had overnight), to give it more of a boost at start up and thereby get up to speed. They didn't recommend that of course as they said it would put more heat in the windings and potentially shorten their life. I'm still thinking that one through, as adding some extra capacitance in parallel with the 80uF one fitted....maybe increasing its value by 25% say....could get me over the hump without too much pain. I'd welcome your thoughts on that one.

On a related front, having run the machine for ten minutes yesterday cutting some oak for the tests, I noticed the shell on the larger of the two bearings (on the pulley side) was quite warm to the touch. I may have under greased it, but maybe I'm getting some friction in there which is making my load a little too high.

The bearings were unchanged by me as they seemed nice and tight, and I thought they were therefore best left alone. I cleaned them out thoroughly with paraffin, and then loaded them with special high speed grease. I then pumped more grease in via the nipples after assembly. No idea how much grease is in there now, or how much to fill them.....I know you're not supposed to overdo it.....so if you have any thoughts on this, that would be great too!

Graeme