speed controlling a motor

[rtbcomp]

That sort of reduction would have the motor running at around 5 hz - I would have thought that on a single phase motor your going to have very little torque in that region, added to the fact the cooling fan may not work properly (it won't flow enough air to cool the motor) when run for prolonged periods at that speed.

Yeah - I would guess that's outside a sensible speed range.

 

[daleyd]

Yeah - I would guess that's outside a sensible speed range.

I'd say some sort of mechanical gearing would be best/easiest if you needed to use this motor. Not to say it wouldn't be possible, but there's a few issues to overcome if you decided to go down the speed control route.

 

[dobbslc]

If you use the mountain bike gear set you could have 18-21? Different speeds!

 

[tomsutton529]

Yeah - I would guess that's outside a sensible speed range.

5Hz is 300 RPM.

We do some Condition Monitoring on some belts that are between 6 and 12 RPM, Eriks supply the gearbox's. So maybe with a VFD and a gearbox we can get close to the right speed.

 

[daleyd]

There's no real problem using a vfd down to whatever min frequency you want (not sure about single phase motors as that's not really my area) but if you want to run at low frequencies for prolonged periods then you need to look at force cooling etc. A bit ott for the application in question I would think!!

I've seen a few very slow shaft speeds through some big reduction gearboxes, for things like rotary valves in quarries/cement plants etc amongst others. If you got your arm stuck they wouldn't even think about slowing down they had that much torque!!

 

[tomsutton529]

There's no real problem using a vfd down to whatever min frequency you want (not sure about single phase motors as that's not really my area) but if you want to run at low frequencies for prolonged periods then you need to look at force cooling etc. A bit ott for the application in question I would think!!

I've seen a few very slow shaft speeds through some big reduction gearboxes, for things like rotary valves in quarries/cement plants etc amongst others. If you got your arm stuck they wouldn't even think about slowing down they had that much torque!!

Defo something to have a MASSIVE E-Stop next to. Some of the ones I work on think nothing of shearing a 4 inch shaft.

 

[daleyd]

Defo something to have a MASSIVE E-Stop next to. Some of the ones I work on think nothing of shearing a 4 inch shaft.

 

[Fred H]

When I built one I used the belt and pulleys from a washing machine.
Still had to use a VFD. Made a larger driven pulley which can be used as hand wheel.

 

[500e]

http://www.offroadfabnet.com/forums/showthread.php?t=3403

 

[mike 109444]

Don't forget whatever you use, you will probable need/want to run it in BOTH directions !
Go DC. Get a 24v motor from a mobility scooter. That's what I have been working on (between other jobs) Even use some of the shafts and other bits from the assembly.

 

[HughF]

This already has forwards/backwards and has a built in epicyclic... Pete, I don't think a single phase out vfd exists... Can we get a 3 phase version of that sky hook?

Venice is a right dive btw... Lol

 

[normspanners]

you can get variable speed gear boxes the motor runs flat out and you adjust output speed of the gear box

 

[sasquar]

Guys this is some fantastic input, cheers to everyone!! I think for now, having read this thread and learnt a LOT, im going to go back to pure step down via gears etc, with an intermediate shaft, i should be able to get down to circa 6 rpm pretty easily.

I looked at using other voltage motors (this project has been very much on the back burner for a few years) but the biggest issue was always getting a power supply with enough juice to run it, whereas with the 240v winch motor, i can just plug it in when ever i need it!

As hugh says, this already has forwards and reverse as part of the deal, so once we change the hand control out for the foot switch that hugh was going to order a month or so back (!) it will allow us to control it simply and safely. Im keen to keep this project as low budget as possible, partly because im tight as hell, and partly because i like a challange, so the mountain bike gears will be aquired (hugh, thats you again!) and ill start fidding around to see if it can be made to work nicely. If not then ill quit buggering around and look for a more suitable motor!!

 

[rtbcomp]

For the record, you can get single phase VFDs

http://www.invertekdrives.com/variable-speed-drives/optidrive-e2-single-phase/

 

[daleyd]

Be cheaper to buy a new motor and single-3 phase drive - have you seen the price

 

[Shox Dr]

Be cheaper to buy a new motor and single-3 phase drive - have you seen the price

I bought a load of what I thought were 1ph motors with a 630:1 reduction gearbox.(2.06rpm)
Luckily they were 3ph so could be easily controlled via a VFD.

I sent one to Newton Telsa, as I wanted to slow it down even more, with a VFD they had on sale. Had it on test for a week, reported back saying they were well upto the job and were worth over £650 each.

 

[normspanners]

I bought a load of what I thought were 1ph motors with a 630:1 reduction gearbox.(2.06rpm)

even a small wattage motor on 3ph would kick out some serious torque at that reduction !!

as I wanted to slow it down even more,(2.06rpm)

what where you repairing?------------ Big Ben

 

[Shox Dr]

even a small wattage motor on 3ph would kick out some serious torque at that reduction !!

what where you repairing?------------ Big Ben

They are 250w. I can stand on top of the positioner on a speed so slow you bearly know you are moving, just keeps on turning