Thread: Fletty's new shed WIP ....or is it a retrospective??

Originally Posted by Chris Parks

To control a three phase motor from a single phase 240V outlet means the motor must be 240V THREE phase. There is one VFD available from the UK that will run a 415V motor from a 240v supply

i thought the whole idea of a VFD was to run what was a 415v three phase motor, rewired to Delta, from 240v?
I understand that the reconfigured motor with now run on 240v 3 phase. Is that what your statement says? Just wanting to 100% sure.
Cheers

Originally Posted by Lappa

i thought the whole idea of a VFD was to run what was a 415v three phase motor, rewired to Delta, from 240v?
I understand that the reconfigured motor with now run on 240v 3 phase. Is that what your statement says? Just wanting to 100% sure.
Cheers

That specific VFD takes the 240V single phase, transforms it into 415V, and then creates the 3 x 415V Phases.

It just so happens that when a 415V 3P motors, initially wired as Y, are converted to ∆, they run at full power on 240V 3P.

You may see example on the web showing a 240V SP motor running with a VFD plus a few bibs and bobs, but its a complete kludge and you can't full power out of the motor

Originally Posted by BobL

You may see example on the web showing a 240V SP motor running with a VFD plus a few bibs and bobs, but its a complete kludge and you can't full power out of the motor

There was a DIY kit a few years ago. Can't comment on how good though.

I saw that a while back but the literature says it can't be used on a motor with a centrifugal switch so that rules out motors like those used on my dusty etc.

Originally Posted by apple8

There was a DIY kit a few years ago. Can't comment on how good though.

That is basically a VFD.
If you know what you are doing it's not that complicated to remove the centrifugal switch on and SP motor.

It drives both single and 3phase motors and claims a 96% efficiency, but that will be for a 3Phase motor.
Efficiency will be less for a single phase motor.

With VFDs costing ~$150 the cost of components to build that kit is no going to be cheap either.

Originally Posted by BobL

...........but its a complete kludge and you can't full power out of the motor

Ive just got the grandurchins to bed after reading many many stories. I've read nursery rhymes, fireman Sam, Peter Rabbit, Noah's Ark........ but nowhere did I see a "KLUDGE"......?

So a VDF CAN control a single phase motor?
Maybe there should be a thread somewhere on VFDs so all the info can be in one spot.
There are references through a lot of threads, some with conflicting info, so it would be nice to have some definitive answers, as I can see this being a popular addition to many workshops.

Originally Posted by Lappa

So a VDF CAN control a single phase motor?

Yes but I see no reason to do this - in fact I can see lots of reasons not to do, it ESPECIALLY on a DC.

If the motor is never under more than half rated power loads if may be possible to get away with a VFD and an SP e.g. a 3HP lathe and you want to turn pens
But lets say you have a 2HP single phase DC and you want to drive it faster with a VFD.
You will need a VFD - ca-ching $150.
A few bits and pieces - maybe $20
What you will end up with is a n underpowered motor that "under load" can't reach full rpm let alone operate at any higher speeds that you want.
This leads to serious motor overheating and seizures - ca-ching.
Or worse it ends overheating and sets fire to your workshop - CA-CHING

So you try get around this by buying a more powerful single phase motor - Ca - CHING.
Now you might need a dedicated 15A circuit - ca-Ching
This is just plain nonsense.

The way to do it is to replace the 2HP SP motor with a 2 HP 3P motor - new they're usually cheaper or about the same as a SP motor anyway.
Hook that to a VFD and everything is sweet.

That's what I did to my DP, BS and Lathe.

If you know what you are doing then used 3P motors represent a reasonable pathway.
3P motors are much simpler devices and last much longer than SP motors so a used 3P is likely to be in better shape than a used SP motor.
Somewhere on these forums I have posted my used 3P motor purchase history. They range from 1/8 to 5HP and price ranged from FREE to $70 with an average price of about $40.

BTW please not my signature.

Bob, I was looking at controlling the speed of devices other than a DC, eg. a 240v drill press, as you suggested in another thread.

Originally Posted by Lappa

So a VDF CAN control a single phase motor?
Maybe there should be a thread somewhere on VFDs so all the info can be in one spot.
There are references through a lot of threads, some with conflicting info, so it would be nice to have some definitive answers, as I can see this being a popular addition to many workshops.

Im happy to start a thread titled VFD CASE STUDIES and repeat this history to date but under which forum (fora?). I imagine the mods will want to put a caveat on it but all I will detail is the history of this particular conversion. As Bob said above, 3 phase motors are mechanically and electrically less complex and therefore should last longer. In my case, I bought a second hand device with a NON STANDARD 3 phase motor already fitted and hence a VFD was my only reasonable option. As it turns out, even if I had been able to refit the DC with a STANDARD single phase foot and flange motor ($268), a VFD at $170 still steals the cake.

fletty

Your experience is the reason I'm interested. I have discarded 3P machinery in the past which was at a very reasonable price.
I would also like to know the full range of uses of a VFD, such as my example above, of a DP.
I would rather get the info from people actually using the devices rather than a maybe dubious discussion/paper etc. elsewhere on the WEB.
I'm not that interested in how to wire one up etc. so that shouldn't peeved the Moderators, I just want some reliable information on uses, what to look for when buying 3P equipment, ratings of equipment vs VFD specs etc.
Some posts in this thread show conflicting views so it can be confusing for newbies like me so it would be good to have a thread with reliable information and people's actual experiences.
Cheers

Originally Posted by fletty

Im happy to start a thread titled VFD CASE STUDIES and repeat this history to date but under which forum (fora?).

Even though I know few folk visit there it should probably go in the electronics forum.

Originally Posted by Lappa

Bob, I was looking at controlling the speed of devices other than a DC, eg. a 240v drill press, as you suggested in another thread.

That would mean you'd only be able to use small bits, no large Forstners or hole saws in wood, or larger bits in metal.
I still reckon if a VFD is going to be used it might as well be done properly.

I have been asked ("if I don't mind") to discuss the costs of the whole DC upgrade project. Here are the costs of the key elements but I can't list the Bunning minor purchases on the way?

• Second hand (abused) 3 phase 3hp double filter bag DC = $450
• 1 pleated canister filter ex Carbatec ~ $260
• second pleated canister filter transferred from existing 2 hp DC = NIL
• Cost for motor rewinder to bring out the star point and replace bearings = $150
• VFD ex eBay = $170

The existing acoustic enclosure was too small to house the new 3 hp DC and so has been both rebuilt and relocated

• I have been able to reuse the acoustic sealed door and door frame, probably 75% of the timber frame, 100% of the acoustic batts and 50% of the plywood, cost = NIL
• colorbond cladding left over from shed build, extra cost = NIL
• new plywood, 4 sheets at $43 = $172
• additional R2.5 acoustic batts 2 packs at $120

To reroute, extend and convert all of the ductwork to 150mm used mostly fittings I had from earlier layouts but required about 2 metres of duct, 2 more Y's and 2 X 45 deg elbows ~ $150

I haven't added it all up because, as we all know with a passionate hobby, spending on 4 items that add up to a $1000 doesn't feel anywhere near as bad as a single purchase of $1000?

fletty

Originally Posted by Lappa

Some posts in this thread show conflicting views so it can be confusing for newbies like me so it would be good to have a thread with reliable information and people's actual experiences.
Cheers

What posts are causing you confusion?