E bay Band saw near Sydney

[auscab]

This looks like a nice old style band saw for some one to do a swap to single phase from 3 phase. 250 mm depth of cut.

http://www.ebay.com.au/itm/150778501022 ... 1423.l2649

[woodrat]

Hi Rob, Well Spotted. I saw this last night too. I have seen one of these machines before and I wish I had bought it. They are very robust. I think made in Australia probably in the 50s. The one I saw was a bit rough in the castings like a lot of early (post WW2 early) Aussie machines but the engineering was top shelf. I am sorry I cant buy it....no budget for tool purchases and I already have 2 bandsaws....

John

[woodrat]

Also Rob, Variable speed drives are quite cheap now on eBay so a motor change may not be necessary...

[auscab]

Yes that's a possibility, I have just fitted one to my face plate lathe . the motor has to be Delta wound though. from what I know,to tell if it's delta wound you should see 6 wires that come out from the windings that go to 3 terminals.
There could be more to it than that though.

The one I fitted to the lathe was not delta wound ,and it cost $75 to convert.

The guy who did it said if he could not reach the wires to make the additions he would have to re wire the whole motor. its a big old 3 phase 3 hp .I said how much for that ?
He said $ 200. To me it looks like a lot more than $200 worth of time and Copper wire.

[liam_fnq]

Three phase motors are all the same. Star or delta is all in the way you hook it up.

For those who have a three phase supply, three phase machines always trump single phase. For a given HP, three phase motors are smaller, quieter, last longer, use less power and are more efficient.

[auscab]

Hi Liam, you may be talking forward or reverse . you just switch the wires.
What John was talking about is a box that plugs in to 240 volt that turns that currant to 415 volt ,so its an inverter as well as giving speed control. The one I connected the other day ,because of the pulleys gives me from 70 rpm up to 300. I can dial in from 0 up to 50 hertz. maybe more ,I'm not sure. It's all new to me and it's a complex set of instructions.
The one I got it had to be delta wound. six wires out to come together as three .

[liam_fnq]

Hi Liam, you may be talking forward or reverse . you just switch the wires.
What John was talking about is a box that plugs in to 240 volt that turns that currant to 415 volt ,so its an inverter as well as giving speed control. The one I connected the other day ,because of the pulleys gives me from 70 rpm up to 300. I can dial in from 0 up to 50 hertz. maybe more ,I'm not sure. It's all new to me and it's a complex set of instructions.
The one I got it had to be delta wound. six wires out to come together as three .

Obviously in practice you got it right, however your terminology is all over the place.

Changing the polarity will reverse a 3 phase motor. As you stated.

You can't change current to voltage. Current is current and voltage is voltage. They related but not at all interchangable.

An inverter changes DC to AC. Lots of machines use inverters these days because of the control that can be had over the sine wave.

I've never seen a three phase motor that was set up any different than all the others (that's not to say they don't exist). Six wires coming out of three windings. You can hook it up in star or delta depending on what you want.

[auscab]

[quote="liam_fnq
Obviously in practice you got it right, however your terminology is all over the place.

Changing the polarity will reverse a 3 phase motor. As you stated.

You can't change current to voltage. Current is current and voltage is voltage. They related but not at all interchangable.

An inverter changes DC to AC. Lots of machines use inverters these days because of the control that can be had over the sine wave.

I've never seen a three phase motor that was set up any different than all the others (that's not to say they don't exist). Six wires coming out of three windings. You can hook it up in star or delta depending on what you want.[/quote]






Ok thanks. I dont have a clue about this stuff.
My motor had three wires and needed surgery though, and now it works.

And you are saying that most of the time you will find six wires out of three windings ?

[liam_fnq]

yes, each winding has two wires. what you do with them determines what configuration the motor is wired in.

[woodrat]

Hi Liam, you may be talking forward or reverse . you just switch the wires.
What John was talking about is a box that plugs in to 240 volt that turns that currant to 415 volt ,so its an inverter as well as giving speed control. The one I connected the other day ,because of the pulleys gives me from 70 rpm up to 300. I can dial in from 0 up to 50 hertz. maybe more ,I'm not sure. It's all new to me and it's a complex set of instructions.
The one I got it had to be delta wound. six wires out to come together as three .

Rob, I think that some modern inverters change the power to 3 phase but it is 240 volt 3 phase and the inverter needs the motor to be wired in delta which would mean that it is a 240 3 ph motor now. I had an old jointer a few years back that ran on that type of motor controller....I stand to be corrected though as I am no sparky!

John