Thread: 240V 1-phase to 415V 3-phase vfd

Just to mention an alternative to VFD, in the form of an advanced rotary phase converter sold by a Victorian company. It automatically switches balancing capacitance according to demand.
On special today and tomorrow only, not cheap but looks a quality product: www.phasechanger.com
The smallest one is nearly $2,000, probably too much for limited use but that's with 20% discount. Could solve my 3 phase needs forever, if I could afford it. Still, I was quoted over $10,000 for mains 3 phase power.

Jordan

Hi Keith
That name plate is off a dual voltage motor, neither mine nor neksmerj's motor is dual voltage. Either the star point is buried or they are wired in delta already.
Stuart

Hi Ken,

Sounds like removing the motor is, "a bridge too far", to use the popular expression.

I think you can be 99% confident that your motor is dual speed star wound. If you aren't going to pull the motor, then your next lowest cost option is to use a 240v 1ph in 240v 3 phase out.

You won't see any loss of power with the vfd running at lower Hz, (say 25Hz) maybe you can compensate for that by selecting the 2 pole winding on the motor (hi -speed).

Just remember DON'T go switching from 2 to 4 pole, with the vfd running..

Regards
Ray

Hi All,
I understand that this is a Two Speed Motor and probably Star Wound.
There could be a good chance that it has an internal Star Point, if so then one could choose which winding they want to connect the VSD to and this then could work.
I would recomend checking the Windings via say a metering it to confirm this.
I attach some Two Speed Circuit Diagrams for anybodys referance who would want them.

Regards,
Keith.

Keith_W

Would you care to expand on your comment re checking the windings by metering.

Is there a way I can determine if my motor is star wound, or delta?

To recap, the motor has only three conductors plus earth in the lead. No neutral conductor.
The nameplate specifies 415V 3-phase. ie, it's not dual voltage.

I really don't want to pull the stator out, if I can help it.

Ken

Originally Posted by neksmerj

No neutral conductor.

Regardless of how the motor is wound (star or delta) there is no need for a neutral conductor. I don't recall ever seeing a 3 phase motor that required a neutral. Neutral is normally only used in single phase applications.

Hi Ken
I've just read through both threads concerning this mill.

As far as i can see you have a couple of options.
The motor you have is a 2 speed 415V 3 phase motor. Almost certainly containing two sets of windings connected in star. Your wiring diagram would look very much like one of the ones posted by Kieth.
Two simple options, I say simple because they don't involve altering the mill at all, are to have 3 phase connected to your house or to purchase a 240V single phase to 415V 3 phase inverter, from England it seems.
While the cost of having 3 phase power connected may seem restrictive, once you get over the reaction, it can be recouped by having acces to many other machines that you previously wouldn't have bothered with. 3 phase machines often go cheaper because the market for them is limited. You also need to factor in the cost of having at least one outlet and a new distribution board/mains install in your shed.
Purchasing the inverter would be the best all round option for price and convenience. Although moderately expensive, if you oversize it a bit you can use it on other 3 phase machines you may wish to purchase (cheaply ) You can wire a socket to it so changing machines is a matter of unplugging and plugging in.

The final option on 'no change to the mill' is to purchase or make a rotary phase converter.
Again, handy for the future as long as it is suitably sized but expensive and a large footprint if space is at a premium.

I think you have a further 3 options that include modifications to the mill.
The first is to dig out the star point of one set of windings and bring it out to a terminal box so that a 240V single phase to 220V 3 phase inverter can be connected in delta. This means you would have to do away with the second set of windings and would rely on the VFD for speed control. You could possibly do both sets of windings and have a greater control over speed/torque/power but you would really need to speak to a motor rewinder about that one. If choosing one set of windings to operate from there are pros and cons for each set. I think some of the other guys covered the basics in the other thread.
The second option is to have the motor rewired to run on 240V single phase or single speed 220V 3 phase. Again talk to a profesional motor rewinder if these options appeal. I don't think it will be too expensive.
The third and final option, as i see it is to mount a seperate motor to directly, or via pulleys, drive the existing motor shaft. Motor can be single phase or 3 phase 220V capable with a VFD. A bit of engineering and ingenuity involved but not too hard.

Sorry for waffling so long. Just trying to pull the collective knowledge into a summary that may help.
Edit: And as Vernon said, the neutral has no bearing on this machine. Not required unles you have the motor rewound to 240V single phase. And while i'm here a step up transformer is also not an option, it doesn't work like that. I think Stuarts VFD can run from either 240V single phase or 220V 3 phase input, not 415V single phase as mentioned somewhere else in this discussion.

NCArcher Well put

Originally Posted by NCArcher

I think Stuarts VFD can run from either 240V single phase or 220V 3 phase input, not 415V single phase as mentioned somewhere else in this discussion.

Yes

Stuart