Changing a 3 phase drill to single-how practical is it?

[snowcat]

Thanks, as I suspected. Now I'm getting confused by converter types. Speed controllers, digital inverters, static converters, rotary converters. The only info that I can find is from manufacturers, and obviously, whichever one they sill is the best!

I think I'd ruled out static, and speed controller ones seem to need a lot of rewiring, so I guess its rotary. Shame, as they ain't cheap.

Anybody know if one of these or similar (suitably rated of course) would do the job? I'm guessing its a static converter, so will only run motor based equipment (e.g. no good if I ever ended up with a 3 phase welder).

Regards,

Phil

Pie man they are suppriseing easy to make, out an old 3 phase motor which you can normally pick up for next to nothing, I think I used a contactor and a few caps, and thats it, under £40 the lot proberbly......

I had no use for one as Im all 3 phase anyway, but knocked it up for a freind of mine.....

 

[piman]

Hello Snowcat,

I know that rotary converters use a three phase motor, a large inductor and capacitors but what I am saying is that you can't drive a three phase squirrel cage (the most common type) motor and get three phase out.
However the inverter has so many advantages over a make shift rotary, that it is a non starter in my opinion and not as expensive as you may think for a low output one suitable for a pillar drill.

Alec

 

[snowcat]

sorry pieman was actualy storm monkey I was going to quote,.......you buy what you want pal....

Storm money if your thinking of making a rotary converter theres loads of stuff on the web.......I was surprised how easy it was, I know a fair bit about contact-ors and wiring 3 phase but little about electronics, but really it didn't matter...

 

[MrFluffy]

Just to add something into the mix at this stage...
Most phase converters when going from single to 3 phase output offer some sort of vfd facility. Thats variable frequency drive, which means you can dial in the speed the motor rotates at on the vfd itself, without having to mess round changing pulleys.
Now, there are two types of vfd, the first older type doesn't offer the same torque settings throughout the speed range, in fact if you run a motor at half speed it is half as strong as it should be.
The second type is what are known as vector drives.
It does this by keeping in mind that magnetizing current always lags (inductive) the voltage by 90 degrees and that the torque producing current is always in phase with the voltage. It controls the magnetizing current (usually named Id) in one control loop and the torque producing current (Iq) in another control loop. The two vectors Id and Iq, which are always 90 degrees apart, are then added (vector sum) and sent to the modulator, which turns the vector information into a rotating PWM modulated three-phase system with the correct frequency and voltage.

As soon as a deviation from correct speed or torque or magnetizing current is detected by the control loops the corresponding variable will be changed by the controller to correct the variable.

I have a altvar vector vfd to go onto my wood bandsaw to drop the blade speed for metal, although I have the 3ph->3ph version as I have 3ph in my shed. Im just wiring one into the shaper, as it gives me jog and soft start too... I just paid 90e for a 3kw capable 3ph vfd off ebay...

 

[steve238]

Very interesting post MrFluffy.
I have a couple of questions i wonder if you could help me with?.
Firstly on my single phase Viceroy (pictured on page 1 of this thread) i would like to be able to get the minimum spin speed down from 420 to 200ish ? as long as it could still produce the same amount of torque?,so is it possible to get a device to achieve this (even though i'm not changing phases).
Secondly i'm thinking of getting a big old 3 phase Meddings pillar drill that already has a low minimum spin speed of about 100 and would you be able to point me in the right direction of what 'vector drive converter' would be a good choice as i don't have 3 phase,and a rough idea how much these devices cost and are they easy to wire up?.
Oh how i wish i knew more about electrics.
I think it's safe to say i could write a page on what i know about electrics and an encyclopaedia on what i don't lol.
Cheers Steve.

 

[MrFluffy]

Afaik vfd's need a 3 phase load.
The single phase vector drives take a single phase input, convert it to 3 phase output and furtle with the timings to change the speeds as above. So you would have to swap your motor out for a 3 phase unit if its already a monophase one.

For the 3 phase pillar drill, its dependant on the hp/wattage of the motor which drive you require. They are usually rated in watts they can support as a load, as part of the electronics are switching transistors that can only handle up to a certain power level. You want more power, you have to pay for bigger innards.
If its a meddings procera, I think they come with a 1/4 or 1/2hp motor. Also if its a procera, check if it has a morse taper quill or not, as lots of them didnt to save costs, thus reducing its usefullness
For ease of wire up, its just screw terminals on the device itself with instructions on what connects where...

Generally I watch ebay, when a vfd comes up that fits my power requirements for the machine in hand, I look up its specs at the manufactureres website and make sure its a vector unit. You can get incredibly complex ones with soft start and spindown (with a over ride for emergency use).

 

[steve238]

Thanks for such a detailed reply mate.
Like they say,you learn something new everday,my problem is i'll of forgotten it all by tomorrow

 

[bigdavesproule]

a phase convertor can be made using an old welding transformer to create 415 volts and a capacitor to create a 3rd pahse and the idler motor stabilises it, when the drill or lathe is started the start circuit switches in the start capacitator to increase the current. i have the full plans and details if anyone interested. very long but very interesting lol

hope its useful to some1