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Startrite tilt Arbor motor

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Ttrees

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It seems a VFD could be a suitable thing to do if the motor is 3 phase one, and has never run right.
Although the user name Matthew Woodworks has a catchy name to it, which might suggest he as a business?
VFD's aren't compliant with health and safety 10 second machine stop and isolated from the mains rule.

Kinda sounds like someone doctored a 3 phase motor to run on household voltage 240v with some other way of starting it, and is possibly wired to 380v star which would explain no power or torque.

Sounds intriguing
Tom
 

Ttrees

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Just seen you are using a 3 phase supply.
Is the motor configured to delta or star?
Tom
 

Matthew Woodworks

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If possible I'd prefer to return it back to 240v single phase if that's possible? Maybe a new motor? Keep the switch mechanism if possible?
 

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Matthew Woodworks":25wxi9ri said:
The saw was kind of inherited rather than bought and prior to the new motor being fitted it was also sluggish back then I remember and the 'new' motor made no difference to its performance - no wonder I can see now. It's always, with me anyway, run on 3 phase. The saw was rarely used a(as we have 2 much larger panel saws) and it hasn't been used for a few years and was in danger of being buried in a dark corner of the workshop! So I wanted to have a go at working out how to get the poor old thing working properly again as they are fab little saws.

I can't see what the other questions where on the thread as I write this so I hope I've not missed anything!

I'm not really sure how to move this forward!! What's the plan I wonder? I need to swat up more on 3 phase as I find it rather murky and I've always just nodded along when sparks come and fit new machines etc :). I would really like to get the saw cleaned and repaired and up and running as it would be a useful machine in the workshop.
From your photo, you have a 400v 3 phase 2 pole 2 hp motor which is way more power than startrite designed it for at 1.2 hp so it should be fine.
Either the motor is faulty which is pretty unusual for a 3 phase machine or maybe only two phases are connected.
You said it was a poor performer before the motor change so is there something mechanical wrong? I had someone the other day complaing of poor saw performance and it ended up being the blade slipping so consider everything no matter how unlikely.

Collectively we have wasted a fair bit of time/thought on this based on your original question so lets try and move this forward with some sound information.
 

Ttrees

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It looks like it was always a 3 phase motor, the machine could have had an original single phase motor before.
Have you a business or shared workshop that you intend to run the machine in?
That will either mean a RPC to run 240 delta low voltage three phase machines in a business
or a motor swap.
If a home workshop a VFD might be a cheaper solution.

Tom
 

Myfordman

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Matthew Woodworks":1hd3z4mj said:
If possible I'd prefer to return it back to 240v single phase if that's possible? Maybe a new motor? Keep the switch mechanism if possible?
Nope everything from plug to shaft needs to be replaced if you want to run on single phase. You have an imperial bs5000 motor on there and so to keep the pulley un modified you need a new imperial motor which cost typically 75% more than an equivalent metric motor.
I suggest you have a good hard think about which way you want to take this at an affordable cost.
 

Distinterior

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Ttrees":205yj7bj said:
It looks like it was always a 3 phase motor, the machine could have had an original single phase motor before.
Have you a business or shared workshop that you intend to run the machine in?
That will either mean a RPC to run 240 delta low voltage three phase machines in a business
or a motor swap.
If a home workshop a VFD might be a cheaper solution.

Tom
Tom,....Why dont you try reading the complete thread first...?? Of course the saw had a single phase motor originally....It says so on the Startrite model tag....
 

Ttrees

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Sorry thought you guys had it sorted, my bad.
I just seen a few of you knowledgable folks reply and thought I'd try and eliminate something so you folks
can get onto the good stuff. :)

All the best
Tom


Tom
 

Trevanion

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This has been a great thread to watch, I'm no electrician but I can almost feel the frustration :lol:

If you're going to convert it back to single-phase power via motor swap you'll need a new (or old but working) motor that fits the mounting plate, and then you'll also need the motor to have the correct size shaft diameter for the pulley and also the correct size keyway for the bore. In an ideal world, you need to pull the existing motor out and measure the hole centres in the base of it and also how far back the holes are from the shaft shoulder to be able to find a motor that'll fit just right on the plate, and then measure the shaft diameter and keyway and select your motor. A new motor will probably be around £150-200 or more depending on the brand, you could pick up an old one pretty easily but this could be hit or miss in regards to how much work it's done and life expectancy. It's fairly straightforward whilst at the same time being quite difficult.

If you're pretty practical you could probably make most motors fit with a bit of engineering without having to find a totally identical match.

From experience, I wouldn't bother putting a motor any more powerful than 1.5kW as the 9" blade can only cut so much regardless of how much power you input. If anything, I would probably stick a 1kW motor in there just as Startrite sort of intended, it would be plenty enough power and it would cost less to run. I've used a few different saws over the years and I can't say I ever really noticed much difference between a 3HP motor versus a 5HP motor on a machine running a 300mm blade, they both bog down about the same due to the blade only being able to cut so much, it's just the 5HP motor is more likely to throw the workpiece back at you than stall out if you push it too hard.

You'll also need a new single-phase switchgear, these aren't overly expensive or too complex to wire up. If you buy everything new, motor, switchgear, glands, cable and plug... you're probably talking around £300 if you're buying decent stuff.

*Edit* Myfordman is very correct about the imperial shaft, that'll be an expensive nightmare to get new unless you can rebore the pulley to a nearish metric size or have a new one made.
 

Matthew Woodworks

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Can I thank everyone for all their invaluable advice. Seems it's a pretty complex issue to unravel. I think with things as they are at the moment I might just let the saw slip back into that 'not sure what do with' corner of the workshop and maybe when I've less work on will try and pick this up again. If only I had the knowledge of you chaps out there! I clearly need to educate myself further with all the aspects of this - or I might just stick it on eBay with a very (now even clearer!)description of what is right and what is wrong about the saw.

Thanks again so much and best wishes to all at this time....
 

Ttrees

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So you have a three phase motor that will be in this workshop (a professional business)
Why is it important to have it running from single phase?


It seems to me from my not too knowledgable perspective
that inside the motor terminal cover, it is configured to high voltage 3 phase Star, and the workshop is supplying 3 phase
low voltage delta.
Just a guess though.

Please confirm where this machine is to go, i.e a business, or a hobby shop, as that will be important on the
advice you will get from the folks whom have been trying to help you.

Myfordman AKA Bob Minchin is a serious motor guru, and his writeup on induction motors and VFD's opened up
a world of equipment that suddenly was a choice for me, and for that I am very thankful.
Cheers
Tom
 

Matthew Woodworks

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Hi Tom,
It's to go in a shared workshop - where 3 of us work together on our own projects. I had thought maybe this was too complex to resolve (for me anyway) but maybe I started to think the wrong way when I thought of taking it back to 240v and the way forward might be to just fit a suitable capacitor (as first suggested)? Keep it on 3 phase which we have here and just fit the correct capacitor?
Would that work?
 

Myfordman

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Ttrees":3lhig1dn said:
So you have a three phase motor that will be in this workshop (a professional business)
Why is it important to have it running from single phase?


It seems to me from my not too knowledgable perspective
that inside the motor terminal cover, it is configured to high voltage 3 phase Star, and the workshop is supplying 3 phase
low voltage delta.
Just a guess though.

Please confirm where this machine is to go, i.e a business, or a hobby shop, as that will be important on the
advice you will get from the folks whom have been trying to help you.

Myfordman AKA Bob Minchin is a serious motor guru, and his writeup on induction motors and VFD's opened up
a world of equipment that suddenly was a choice for me, and for that I am very thankful.
Cheers
Tom
Thanks for your kind words Tom!

In UK and most places other than those with a US based power distribution system, three phase is always ~415v leg to leg which gives ~230v leg to neutral for domestic installations.
It is exceptionally unlikely that the OP has a 230v three phase system in his workshop.

The latest version of my motor write up lurks here:-
https://drive.google.com/open?id=0B_GZr ... ldlQjJtUDQ

My suggestion to the OP is before consigning the saw back to the corner of the shop, is to investigate why the performance is pi88-poor - could be mechanical and readily solved.
 

Myfordman

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Matthew Woodworks":3aue0p0j said:
Hi Tom,
It's to go in a shared workshop - where 3 of us work together on our own projects. I had thought maybe this was too complex to resolve (for me anyway) but maybe I started to think the wrong way when I thought of taking it back to 240v and the way forward might be to just fit a suitable capacitor (as first suggested)? Keep it on 3 phase which we have here and just fit the correct capacitor?
Would that work?
No, a three phase motor running on a three phase supply does not require any capacitor to make it work.

For info.

A single phase motor for something like a saw, DOES require at least one capacitor to make it work on a single phase supply and this is an item that is a fairly common failure mechanism.
It is possible, but not recommended unless you know what you are doing, to run a 3 phase motor from a single phase supply and this requires one prefereably two capacitors but the results are never as good as a proper 3phase supply.
A converter extends this principle into a semi hernia inducing lump but still is not a perfect solution
The best solution by miles to run a three phase motor from a single phase supply is to use a box of electronic known as an Inverter (as distinct from a Converter)or Variable Frequency Drive VFD.
These take a bit of knowledge to set up out of the box and need to be selected to match job but work very well indeed.
 

Ttrees

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Now take my writing up as something that defiantly needs clarification, hopefully from the folks
above. !!!!!!!
Edit : Clearly I have the wrong idea on why a motor has dual voltage capability :oops:


Its a three phase motor Matthew, not a single phase one.
The absence of the capacitor will be evident on a 3 phase motor, even if it didn't have a readable nameplate, you could be sure it was a three phase motor by this.

There's no point in trying to make it work on single phase
when you have a three phase supply, with 3 phase motor and switchgear already installed....

If the saw were going to a small home shop hobby style without any other machines
then it would be a VFD as it would be the cheapest/most suitable way to get a three phase
machine running from household supply.
(not compliant with health and safety)

While your taking pictures, make sure the machine is isolated (plugged out)
I suggest you have a look at the motor terminal box , 4 screws to remove cover.
I suspect that the configuration of the terminals is orientated to Star 380 volts or thereabouts,
and the 3 phase supply in the shared workshop is on 240 volts delta.
(just a totally uneducated guess, as I know absolutely nothing beyond VFD's for simple machines)

I have read that if you have a 3 phase motor orientated to star, but you only have
3 phase supply that is delta configuration, then loss of torque is a result.
It is the case if you were running a VFD/inverter like I do in my hobby shop.

If this is the issue, then other folks will be able to clarify if I could be onto something.

To check which orientation the motor is configured can be done at a glance, whilst the machine is isolated,
and takes about a minute to switch from star to delta configuration.
Take a look at Bob's Induction motor PDF
It has clear diagrams on star and delta configuration.
He is an admin on thewoodhaven 2
goes by the handle 9fingers, and the induction motor PDF
is underneath his signature.
(I cant get the PDF to link)

Hope this clears things up a bit for the knowledgable folks to give a more detailed reply on
anything important.

Tom
 

Myfordman

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Tom, No European distribution system that i know of supplies 240v 3 phase.

You regularly point out about vfd not being compliant with health and safety. I've never seen this other than tracing back to you. I'm interested to explore this so please can you point me at a justification for this please so that I can follow this up. (pm if you like rather than divert this thread?)
 

CHJ

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Ttrees":1yd546p8 said:
…..
and takes about a minute to switch from star to delta configuration.
Two things:-
1. as Bob has said the 3ph shop supply will be nominally 400 volts. UK power distribution does not provide 230-250 volt 3ph supply.

2. the Motor Plate image that the OP has posted from his motor shows that the motor is a single standard 380/400 volt STAR wound motor as manufactured. It WILL NOT have any links (commonly six connection points) in its connection box to allow easy configuration for nominal 250 volt delta connection.

This can only be changed by someone getting into its internals to find and retrieve the star point connections (if possible) and bringing them out to the connector box to allow the motor to be run from the more readily available 240volt 3ph vfd's. in delta mode.

If the current motor is proving to be under powered in use then there would be no point in converting it, it won't provide any additional power running from single phase, maybe even less.

If on the other hand there is a mechanical reason such as a blade slipping as already mentioned way back in the thread by Bob or the blade is ridiculously blunt then fixing those problems stands a chance of making the machine usable.
 

Ttrees

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Myfordman":3m4t8i6x said:
Tom, No European distribution system that i know of supplies 240v 3 phase.

You regularly point out about vfd not being compliant with health and safety. I've never seen this other than tracing back to you. I'm interested to explore this so please can you point me at a justification for this please so that I can follow this up. (pm if you like rather than divert this thread?)
It's very likely I'm mistaken Bob
I have been trying to find where someone suggested this, but am unable.
Here is something to suggest that you need only a isolator...
https://www.hse.gov.uk/pubns/wis38.pdf

It's probably me mixing things up like having an isolation switch fitted for possible Health and safety rules when they apply,
and good policy for VFD/inverter care and use.
It could be because I ain't qualified to install one of these, or because I may have suggested one of the El Cheapo VFD's ....some without components for an external braking resistor and
some so cheap and tiny that they couldn't have any built in braking capacity, and might not be a match for the stopping inertia of given machine within 10 seconds.


This is great if you can use a VFD/inverter in business :D
What a boon not either having to do any motor swapping, or being able to rent a unit without 3 phase, if one was doing up machinery and maybe getting started in business.
Hope this is the case, I may have to edit some old threads

Tom
 

deema

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There seems to be a few things getting mixed up.

Line voltage refers to the amount of voltage measured between any two line conductors in a balanced three-phase system. Phase voltage refers to the voltage measured across any one component (source winding or load impedance) in a balanced three-phase source or load.

So, in the UK the ,one voltage is 415V, and the phase voltage is 240V which is measured across any live and neutral / earth.

VFDs are safe to use if specified and installed correctly. They offer a number of advantages over a standard motor start relay
1. The in rush current is limited and dos not create a large spike on the supply.
2. You can use them to brake the motor often with the need to add an external braking resistor to comply with the regulations.
3. Within limits you can vary the speed of the motor (which may affect torque depending on the motor design)
 
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