Thread: Help Converting 2 Phase to 3 Phase

You cant do anything with the 2 Phase unless you run a Phase converter ie $$$$$

Before answering your VFD questions read the document supplied in this thread
VFDs for Newbies

When you say 440V 2 phase, and rural property, I am thinking that the property is supplied via a single line SWER (Single Wire Earth Return). As the name suggests, these supply a high voltage low current via a single wire to a high voltage stepdown transformer, with the primary winding taking the high voltage (up to 9KV so primary current is much lower than the supply current to consumer premises, and relying on the ground to provide the primary return path. The secondary winding of the transformer is effectively a centre tapped 440V winding with the centre tap being the Neutral and the start and end of the the winding being two Actives that are out of phase.

There are VFD's available for this sort of situation, often used for pumps etc., but at a considerable price premium particularly relative to the cheap VFD's often discussed in the forums. I would also suggest verifying the available excess capacity of the supply system and the motor requirements before making a commitment.

You will need to show a picture of the motor data plate to get a good answer. A single phase input VFD will produce 240v three phase, which is different to the native three phase power here.

Some motors can be configured (internally, with different terminal connections) to run on 240v three phase.

Originally Posted by Greg Q

You will need to show a picture of the motor data plate to get a good answer. A single phase input VFD will produce 240v three phase, which is different to the native three phase power here.

There are some 240V single phase input VFD that will produce 415V 3P output. Several MWF members are using the Ecogoo brand of these VFDs and reports are they they work quite well. They cost about 2X more than a standard VFD but there's a lot less mucking about .

Here re some examples
5.5kw/7.5kw/11kw/ 220v single phase input 380v 3 phase output AC Frequency Inverter ac drives /frequency converter 220v/to380v|Inverters & Converters| - AliExpress
Frequency Converter Vfd Inverter 4kw Single Phase 220v Input And Three-phase 380v Output Motor Speed Controller - Inverters & Converters - AliExpress

Ah! Did not know that. Thanks for the link, and the info, Bob.

Also…”Eco goo”. What’s not to like?

Hi Zac, have a rural property as well and just got a quote to upgrade my existing 2 Phase power to 3 Phase, all up would have cost around $6,000.00, rather than spend that much am having some 20 amp plugs installed which is relatively inexpensive and allow me to purchase 20 amp machines with more Hp. Have no idea about the cheap inverters Bob provided a link for but may be worth looking into.

It's possible to make a rotary phase convertor using a welder with a tap to act as a step up transformer giving you 415V (this will be L1) then you need start up capacitors (they only stay in the circuit until the slave is running, so use a momentary switch) to make L2 & L3 (the ghost legs), you then have a slave 3phase motor (mine is 10 hp) once the motor is spinning it generates 3phase power, which can start machines up to 5 hp (50% of the slave motor) Further capacitors are needed to balance the 2 ghost legs these capacitors stay in the circuit while ever the slave motor is running. I built mine using a second hand welder for less than $1k

BTW I too have 2 phase to the property (but not to the shed) they are both fused separately out on the road, so they are a true L1/L2 supply and if I had them in my shed I would have only need to generate the L3 ghost leg.

Thanks for all the information. I have read the VFDs for newbies pdf and reckon there's probably too much faffing with big machines that have multiple motors. The main culprit is a big wide belt sander machine, but there is also likely to be a sliding table panel saw and spindle moulder. I have seen a rotary phase converter online for 2P to 3P. What's the feasibility of using one of these for a couple of machines? Thanks again, Zac

I used to have a RPC to power my Felder combo and a big bandsaw. That was in a rented house in Melbourne.

There are plans around for making your own, or commercial units. I think that old Transarc tradesman welders have a big transformer in them.

Originally Posted by Rudyvm

...just got a quote to upgrade my existing 2 Phase power to 3 Phase, all up would have cost around $6,000.00...

I would have thought that is not unreasonable.

We are considering moving house - and I've warned SWMBO that it may cost $10,000 to $20,000 to have 3-phase installed, if we don't find a place that already has it. And I'm not sure that even that is high enough.

Cheers, Vann.

$6K is a bargain. tell them to take your money