Turing a static phase converter into a rotary

[dan.taylor.1]

Hi folks,

I've a big 12.5hp static and a 7.5hp old 3phase motor I want to combine to make a rotary. Anyone help me to do this. I understand the basics, but seem to be able to find only US information on converters.

I think I need to add a start capacitor to save me starting the slave motor with the switches on the front, and a voltage sensing relay to kick this out when the motor is producing the 3rd phase. Do I need anything else?

Cheers,

Dan

 

[maz0]

Hi folks,

I've a big 12.5hp static and a 7.5hp old 3phase motor I want to combine to make a rotary. Anyone help me to do this. I understand the basics, but seem to be able to find only US information on converters.

I think I need to add a start capacitor to save me starting the slave motor with the switches on the front, and a voltage sensing relay to kick this out when the motor is producing the 3rd phase. Do I need anything else?

Cheers,

Dan

With those powers you might be better with a pony motor.

Watch this guys series

 

[dan.taylor.1]

Yeah I've watched his vids. We've got one 7.5hp and one 10hp at work, ones oldschool capacitors and the other hasa specially would motor and loads of contractors to make it work.

 

[Fazerruss]

Just add an extra socket to your converter and wire it in parallel, simples.
I also fitted VA meters to monitor the outputs but that isn't strictly necessary.

http://www.mig-welding.co.uk/forum/threads/commissioning-my-3-phase-lathe.95187/

 

[Hopefuldave]

Mine has the start capacitor kick in while I hold the button down for a second or so, bit of relay logic so the start contactor doesn't latch but the motor contactor/overload does, neither will kick in until the transformer's kicked in, can't connect the load until the motor's spinning - tried to reduce the initial surge on start-up and now doesn't pop the 40A MCB...

Dave H. (the other one)

 

[Shox Dr]

I have a 7.5hp transwave rotary spitting out 415v. ISTR it uses 5caps and a Broyce control for start up.

‘currently it runs for 20secs then shuts down

It’s been waiting for 5/6yrs for that to be replaced

 

[Hopefuldave]

With those powers you might be better with a pony motor.

Watch this guys series

Horribly inefficient, needs a really big motor as all the input power and a third of the load power are going through only one coil... A hefty transformer (if you NEED 415v like me!) is a lot more efficient, driving a 415v 3-phase motor for the phase conversion. As long as the filthy weather doesn't get in the transformer, slurped a gallon and a half out from under the oil so far

I wonder why it was tripping the RCD?

Dave H. (the other one)

 

[knighty]

is the static converter 415v?

is so, just wire the motor into it permanently... so is spins all the time... I think that'll achieve what you're aiming for?

 

[dan.taylor.1]

is the static converter 415v?

is so, just wire the motor into it permanently... so is spins all the time... I think that'll achieve what you're aiming for?

Yes it's 415v. I'd thought I'd need some way to start the idler motor or do I just leave the SPC set to 7.5hp and run my other machines as normal, the 7.5hp motor isn't going to pull any current with no load on it.

 

[Fazerruss]

Yes it's 415v. I'd thought I'd need some way to start the idler motor or do I just leave the SPC set to 7.5hp and run my other machines as normal, the 7.5hp motor isn't going to pull any current with no load on it.

Yes just wire the idler motor straight to the static converter. The motor will then start up as soon as you turn on the static converter. Then just switch on your machine as normal.
I also adjust the hp switch until it runs smoothly rather than relying on set parameters.

I've also spoken to an engineer from Transwave who agreed the physics of this method is sound.

 

[dan.taylor.1]

Well, bunged a spare face mount socket onto the box in parallel with the output one. Plugged in the motor and off it whirred, nice and quiet, might put some rubber matting under it to stop it vibrating on the concrete. Getting 416, 420 and 383v between phases. Not bad with no tuning. I think it was worse before I put the motor on.

 

[Gareth J]

Well, bunged a spare face mount socket onto the box in parallel with the output one. Plugged in the motor and off it whirred, nice and quiet, might put some rubber matting under it to stop it vibrating on the concrete. Getting 416, 420 and 383v between phases. Not bad with no tuning. I think it was worse before I put the motor on.

Sounds like similar outputs to my static converter (allbeit a much bigger one!)

I went though a similar thought process. I have a drill, a mill and a lathe all plumbed into the converter. All different sizes. Playing around starting and idling different machines, I found I still needed to alter the switches on the box to get the machines to sound the smoothest though.

 

[dan.taylor.1]

I wonder why with an off the shelf rotary there is no adjustment, we run various machines simultaneously where I sub. From a big gear head drill to a massive cold saw and 3 big hydraulic c frame presses. No issue with one firing up and the others running.

 

[Gareth J]

I wonder why with an off the shelf rotary there is no adjustment, we run various machines simultaneously where I sub. From a big gear head drill to a massive cold saw and 3 big hydraulic c frame presses. No issue with one firing up and the others running.

I don't know enough about it! But I'm sure there's a reason, if nothing else, maybe it's a cost saving on electrical switchery.

 

[knighty]

can you fix something to the motor shaft? preferably something heavy? a bit like a flywheel

that should help quite a bit

 

[Fazerruss]

I wonder why with an off the shelf rotary there is no adjustment, we run various machines simultaneously where I sub. From a big gear head drill to a massive cold saw and 3 big hydraulic c frame presses. No issue with one firing up and the others running.

They may have built it voltage monitoring across the output phases to switch in extra capacitors.

These are the outputs from mine when the lathe is running.




The middle meter is the generated phase

 

[dan.taylor.1]

can you fix something to the motor shaft? preferably something heavy? a bit like a flywheel

that should help quite a bit

I could, but I thought the point was the idler had no load making it easier to fire up? I put some heavy rubber from a yard scraper blade under it screwed to some wooden blocks this aft and it shut it right up, no noise at all now which is great. Can't stand needless noise in the workshop, it's why I turn r2 off when Jeremy whine comes on!!

 

[dan.taylor.1]

They may have built it voltage monitoring across the output phases to switch in extra capacitors.

These are the outputs from mine when the lathe is running.

View attachment 216552


The middle meter is the generated phase

I've got some analogue voltage dials I'll have to build a box for. The main converter has a current gauge to show what the input is pulling, spikes at something horrific like 180a when I fire it up, might get a clamp meter and see what it actually does pull!

 

[knighty]

I think (I'm no expert)

the idea behind the idler motor is it helps balance the phases out, if one phase is a bit low or a bit high they even out as the idle motor spins at a steady speed putting a bit more load on the high phase and less on the low phases (or even generating when you start a load up)

but... even if it's undetectable to the eye/ear the motor isn't really spinning that steadaly, if you hook it up to the right gear you can literally see power spikes/vibration etc. as the magnets passes windings - what looks to us as one steady revolution is really a bunch of pulses as the motor shaft is pushed around

adding a bit of mass to it helps it run more smoothly :-)

 

[Gareth J]

I could, but I thought the point was the idler had no load making it easier to fire up? I put some heavy rubber from a yard scraper blade under it screwed to some wooden blocks this aft and it shut it right up, no noise at all now which is great. Can't stand needless noise in the workshop, it's why I turn r2 off when Jeremy whine comes on!!

!!! I've got a chunk of that rubber, never even considered it as vibration damping. Brilliant! thanks for that idea