Bandsaw motor questions

[OxxAndBert]

I had an ancient Thiel vertical bandsaw follow me home the other day. Needs a bit of work but hopefully be a useful addition to the workshop.

Just wanting to clarify my thoughts on the motor. It's a 415v 3ph 1hp. Data plate says it's a star motor, and there are only 3 leads coming out to the terminal block.
I was thinking I might take my first dip into VFDs and install one on the saw instead of running it from my RPC, but looks like it would require delving into the motor innards to be able to convert it to delta (if it's even possible).

Am I on the right track?

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Steve

[BobL]

I had an ancient Thiel vertical bandsaw follow me home the other day. Needs a bit of work but hopefully be a useful addition to the workshop.

Just wanting to clarify my thoughts on the motor. It's a 415v 3ph 1hp. Data plate says it's a star motor, and there are only 3 leads coming out to the terminal block.
I was thinking I might take my first dip into VFDs and install one on the saw instead of running it from my RPC, but looks like it would require delving into the motor innards to be able to convert it to delta (if it's even possible).

Am I on the right track?


If you connect a 240V VFD up to the motor "as is" it will generate about 1/2HP - this will be plenty to cut most sheet/plate, and smaller rod and tube.
To get the motor producing the original 1HP the motor will need to be converted to delta inside the motor.

Just a word of warning, if you are hoping to generate variable speeds using the VFD (this is very handy as it would then be much faster at cutting sheet material) I found old motors don't like being driven too far beyond 60Hz. One motor from an old DP would simply not go beyond about 65Hz.

It may be cheaper and easier to swap the motor out to one that is already convertible inside the connection box.

[OxxAndBert]

Thanks Bob. Good to know I'm sort of on the right track.
I hadn't thought much about the variable speed aspect and was more focused in the flexibility of being able to plug it into a normal single phase 10A outlet rather than having to use the RPC. Variable speed would be nice but not a show stopper.

The external wiring is cactus at present as the old rubber insulation has completely perished in places so I haven't been able to test if the motor even runs!
I guess the practical way forward is to hook up some good cable and test that first. If its stuffed then I'll need a new motor anyway so will just source one that can be run in delta with a VFD - or just convert it to single phase.
After having a 9" Hercus lathe with a 1/4hp washing machine motor for 30+ years I've lost interest in nursing underpowered machines, so probably wouldn't bother with the VFD unless I can get full power out of it.

Any idea how much digging might be required internally to find the star point on this style motor?

Steve

[BobL]

Thanks Bob. Good to know I'm sort of on the right track.
I hadn't thought much about the variable speed aspect and was more focused in the flexibility of being able to plug it into a normal single phase 10A outlet rather than having to use the RPC. Variable speed would be nice but not a show stopper.
Sure I understand.


The external wiring is cactus at present as the old rubber insulation has completely perished in places so I haven't been able to test if the motor even runs!
I guess the practical way forward is to hook up some good cable and test that first.
Before you do that I would test to see what the resistance is
a) between the coils - this should be the same otherwise there is a prob and motor will run hot.
b) from the coils to ground - this should be MEGA ohms if not the insulation could be on its way out. A proper Megger tester should be used but a multimeter reading on Ohms will give you some indication


If its stuffed then I'll need a new motor anyway so will just source one that can be run in delta with a VFD - or just convert it to single phase.
After having a 9" Hercus lathe with a 1/4hp washing machine motor for 30+ years I've lost interest in nursing underpowered machines, so probably wouldn't bother with the VFD unless I can get full power out of it. Any idea how much digging might be required internally to find the star point on this style motor?


These motors are usually quite accessible but if it has ever been run hot the insulation may be carbonized and this makes it really hard to get at it because the insulation won't soften when heated with a hot air gun. I'veposted quite a fe photos of tricky start point excavations on the woodies forum here is one thread
Tricky Y common point excavation (http://www.woodworkforums.com/f271/tricky-common-excavation-188056)

This thread might also be useful as it shows a bunch of VFD installations, pros, cons etc
VFD install summaries (http://www.woodworkforums.com/f271/vfd-install-summaries-213878)

[Com_VC]

I am with BobL on this, I would just source a modern motor, that thing is ancient. You would be able to pickup something up for less than $50.

[GJM]

You can get 240v in 400v out VFDs. I put one on myRF30 drill mill a few weeks ago. Works a treat. It is this one. https://www.aliexpress.com/item/Promotion-VFD-Inverters-4-0KW-Input-Voltage-220V-Output-380V-4KW-VARIABLE-FREQUENCY-DRIVE/32830409238.html?spm=a2g0s.9042311.0.0.27424c4dQHn2FE
about$A300 or $NZ 331. This saves mucking around with the windings.

[BobL]

You can get 240v in 400v out VFDs. I put one on myRF30 drill mill a few weeks ago. Works a treat. It is this one. https://www.aliexpress.com/item/Promotion-VFD-Inverters-4-0KW-Input-Voltage-220V-Output-380V-4KW-VARIABLE-FREQUENCY-DRIVE/32830409238.html?spm=a2g0s.9042311.0.0.27424c4dQHn2FE
about$A300 or $NZ 331. This saves mucking around with the windings.

4KW is over kill for his BS

This one might be better.
https://www.aliexpress.com/item/Inverter-1500-watt-1-5KW-input-220V-output-380V-Variable-Frequency-Drive-for-1-5KW-Motor/32828616363.html?spm=2114.search0104.3.41.53d15eeeRyCu1g&ws_ab_test=searchweb0_0,searchweb201602_2_10065_10068_10130_318_10547_319_10548_5727315_10696_450_10084_10083_10618_452_535_534_10307_533_532_10131_10132_10133_204_5727215_10059_10884_10887_100031_320_10103_448_449,searchweb201603_2,ppcSwitch_0&algo_expid=ec142002-da5f-42e2-a086-d291b8b5d8af-6&algo_pvid=ec142002-da5f-42e2-a086-d291b8b5d8af&priceBeautifyAB=0

@ AU$240 - It is still cheaper to buy a 240V, SP - 240V, 3P, VFD and a used 3P motor that is convertible and would be able to operate over a wider frequency range.

[Chas]

I'm not sure why you have so much enthusiasm for a VFD on a bandsaw. Surely, unlike a lathe, mill or drill, there is no compensation required for the size of the work or cutter. I would suggest your best solution is for a 240V single phase motor of 1HP or perhaps 1.5HP to replace the existing 3 phase motor. There are several sellers on ebay, or you could buy a used one for a lot less than a VFD/motor combo. Just my opinion.

Chas.

[BobL]

I'm not sure why you have so much enthusiasm for a VFD on a bandsaw. Surely, unlike a lathe, mill or drill, there is no compensation required for the size of the work or cutter.

I have seen charts that show different speeds for different sizes of work but perhaps more significantly are the optimum band speeds for different materials

Here are some typical band speeds (in ft per minute)
SS 75 -115
Carbon Steel 190-340
CI 110 - 250
Al 400 450

Some of this is about band longevity which matters less in a DIY situation

[Chas]

Thanks for the information, Bob. It is always good to learn something new. My remarks were in the context of a woodworking bandsaw, due in part to what appears to be a layer of sawdust on the motor as shown in the photos. I now know that a Thiel is a metalworking machine, and was possibly two speed. More details always welcome.

Chas.

[BobL]

Thanks for the information, Bob. It is always good to learn something new. My remarks were in the context of a woodworking bandsaw, due in part to what appears to be a layer of sawdust on the motor as shown in the photos. I now know that a Thiel is a metalworking machine, and was possibly two speed. More details always welcome.

Chas.

To a certain extent WW working bandsaws can also use a VFD. The optimum speed for ripping timber is around 5000 ft/min whereas most WW bandsaws run at no more that 3300 ft/min. I have experience with this running a 27HP Bandsaw mill cutting logs up to 35" wide and can the higher speeds really makes a difference in cutting speed. The reason the higher speeds are not used on smaller bandsaws is these band speeds are pretty frightening and potentially more dangerous and when cutting short pieces is unnecessary.
I put a 3HP motor and a VFD on my (originally 2HP) WW BS a few years ago and it has a speed range of 1000 to 5000 ft/min and confirm it can cut faster at higher speeds. Another advantage of a VFD is it can also be used in conjunction with a braking resistor to rapidly slow down a BS. I did this on a radial arm saw at the mens shed which used to run silently for more than 2 minutes after it was turned off. Now it stops in 4 seconds. I put a foot brake on mine a few years ago and that stops the band in about 3 seconds so I don't need that feature on a VFD.

[OxxAndBert]

Thanks guys - some great info ideas there.
Haven't had a chance to look any further at the motor yet, but did take the opportunity to buy one of the cheap electronic meggers off ebay as I know its something that I'll definitely use again. I need to chase up my father and see if he's still got a real megger from his sparky days that he no longer needs (he lives in NZ otherwise that would have been my first option).

Regardless of which way I end up going with this particular machine, I'd like to know whether the motor itself is any good. Its also a perfect opportunity to learn a bit more, as I'm sure this won't be the last dodgy old motor I ever deal with ;)
Will update once I've the megger arrives and I've had a play with it.

Steve

[OxxAndBert]

Still waiting for the megger to turn up, but just did a quick check of the winding resistance and get around 18ohms between each of the terminals.
Shows open circuit between terminals and ground on a standard digital meter (2000K max range).

Steve

[BaronJ]

Hi Steve,

It would certainly benefit from a good strip and clean up. If you are going to attempt to dig out the star point, be very wary of the state of any insulation in there. You could find that it might have been better just to retire it !

[OxxAndBert]

The megger arrived today.
Checked out the motor - getting around 47Mohms between the windings and motor body.

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Steve

[BaronJ]

Hi Steve,

That looks like a very nice megger you have bought. If I may ask where did it come from and how much ?
My old megger uses a now obsolete rechargeable Nicad battery, it doesn't get used too much nowadays but I do get annoyed when I want to use it and have to put the battery on charge to get 10 minutes use out of it.

[OxxAndBert]

Just a generic Chinese special via eBay. AUD$57 delivered from a local seller.

I checked out a few reviews and seems they are reasonable.
It's got normal voltage and resistance ranges too and I reckon with that huge display (backlit if you want) it's going to get a bit of use in general. Ive got a couple of other multimeters but none have the backlight.
It's only a plastic case so won't take a lot of abuse.

PS. The brand name varies, but they all have the same model number so search on that for info.

Steve

[BaronJ]

Thank you for that info ! I didn't realise that it was a multimeter as well, and the price is right. :U

[OxxAndBert]

Just to round this up, I gave the motor a quick run for a few seconds on real 3 phase (as opposed to what comes out of my RPC).
Didn't want to run it for any longer as nothing has been cleaned/lubed so didn't want to cause any damage.
Will strip it down when I do the rest of the bandsaw and have a quick look for the star point to see how accessible it is, but at least I now know I the motor is good and should run fine on my RPC at home.

The megger is about to get its second job tonight.
I rescued a scrapped 4kw motor with integral brake the other day. The brake was definitely stuffed when I pulled it off, but I suspect its been replaced as a unit just for that and the motor itself is probably fine.
Will be a good score if that's the case.

Steve

[eskimo]

that thing is ancient.

...not as ancient as some of us on here...we can remember when those things were new:D