VFD 1-3PH 240V on 400V motor

[Deadeye]

Just checking: if I have a 3PH 400V motor and I use a 240V VFD to go from 1PH to 3PH, am I correct that the motor will just run at 2/3 speed?
So I can use the VFD to get whatever speed I want (accepting less torque above 2/3 rated speed) and don't need to worry about star/delta?
Finally, is there any advantage/disadvantage to over-specifying the VFD (for example 2.2kW instead of 1.5kW)?

 

[Spectric]

If you maintain the ratio of voltage and frequency then 400 volts at 50 Hertz is the same as 230 volts at 29Hz. I have done this in the opposite direction where you run a 230 volt three phase motor in Delta on 400 volt three phase but at 87 Hz which gives more power from a smaller motor size and constant torque upto 87Hz but also it runs at a faster speed, approx 1.7 times.

If you are looking at three phase machinery then take a look at the digital phase convertor, a much better option which can provide multiple three phase sockets but without the option of speed control and can run much larger loads.

 

[Sideways]

There's no real world down side to overspec'ing the VFD except for the additional cost.
If you anticipate repurposing it on a different motor or machine in future then it's entirely sensible.

You mention not worrying about star delta. If your 3 phase motor is 415/240 dual voltage then it would be better to change it to delta and have access to full power / full speed. Unless you have a particular reason not to.

Either way, and especially if you keep the motor wired in star, you will need to programme the VFD correctly to make this work. Some VFD's don't come with much of a manual at all. Others don't make it very obvious how to setup non standard configurations. I expect that you will in effect be setting the VFD up as if the motor is rated 240V, 29Hz, and full load current approx equal to 2/3 of the FLC at 415V and don't forget to define the number of poles. Once these settings are locked in, you need to set the motor maximum speed which I'd expect to be on another parameter to go past 29Hz and achieve full speed but at reduced torque.

This is similar in some respects to setting up a 4 pole motor which gives full power at 1400rpm and then defining a higher maximum frequency of 100Hz so that you can spin it up to 2800 rpm (the speed of a 2 pole) but at reduced torque.

If this all makes sense, great. If not, get some help. Frying a new VFD is a waste of money and frying yourself is a bigger waste

 

[Ttrees]

Worth mentioning a few things like there being 240v in - 400v out VFD's available,
which some folks on the auzzie forum have been running successfully on lathes.

Also worth mentioning making sure it's possible to enter HP values and amperage
as some don't give that option.

Making sure the VFD is actually the one in the add could be important aswell, as some are micro sized by comparison, i.e the size of yer hand.
Make sure it has the dimensions in the description.

Lastly what comes to mind, kinda relative to what you plan on running,
do you need stop things within some limit, look up "dynamic breaking"
the huanyang doesn't have those bits, just regular internal breaking which ain't bad.
but that's not saying it's impossible to fit those parts,
though just mentioning for interests sake, as the huanyang is quite popular,
and might be worth watching a few videos to get a feel of things.

A little feature what's on another VFD I have, what shares the same case,
is the auto shutoff cooling fan, look up shut up VFD, you'll see it's only a wee part,
Not that I would suggest fitting one, or have done, just mentioning it's a nice feature for a bandsaw, or something else which might be plugged in.
I swapped the Huanyang over to the tablesaw, as I don't mind that machine having an unsettling hum, since I don't use it that much compared.

That's about all I can mention, apart from the very bacics, from a Joe Soap's perspective.
I see some very knowledgeable folks replying, so I'll sit back and try glean some more info.

Good luck
Happy new year
Tom

 

[Deadeye]

Thanks all - really helpful

 

[deema]

Have a look at Digital Phase converters, they create 415V, 3 phase that means you can run any 3ph machine on it, and more than one machine at a time. They usually allow variable speed. They are a bit more expensive than a VFD, but if you need more than one, a Divital phase converter is a better and more economic solution.
Alternatively, the cost of getting 3phase has dropped dramatically. If you thinking of getting an electrical car or air / ground heat pump at some point, 3 phase will be a blessing for rapid charging or ensuring you have enough power for the heating. Three phase motors are more reliable than single phase.

 

[Spectric]

They usually allow variable speed.

Unfortunately this is what you lose compared to an invertor, but is also one reason you can run much larger loads. The inverter rectifies the Ac and then produces all three phases using electronics and has control of both frequency and voltage. The converter though will provide a three phase 400 volt output so you can just use nice decent well built cast iron machinery without any modifications so a win win.

 

[Deadeye]

Have a look at Digital Phase converters, they create 415V, 3 phase that means you can run any 3ph machine on it, and more than one machine at a time. They usually allow variable speed. They are a bit more expensive than a VFD, but if you need more than one, a Divital phase converter is a better and more economic solution.
Alternatively, the cost of getting 3phase has dropped dramatically. If you thinking of getting an electrical car or air / ground heat pump at some point, 3 phase will be a blessing for rapid charging or ensuring you have enough power for the heating. Three phase motors are more reliable than single phase.

Sadly we don't have 3 phases into the house...and it would be a long dig to get it. So no fast charging here for a while at least

 

[Deadeye]

There's no real world down side to overspec'ing the VFD except for the additional cost.
If you anticipate repurposing it on a different motor or machine in future then it's entirely sensible.

You mention not worrying about star delta. If your 3 phase motor is 415/240 dual voltage then it would be better to change it to delta and have access to full power / full speed. Unless you have a particular reason not to.

Either way, and especially if you keep the motor wired in star, you will need to programme the VFD correctly to make this work. Some VFD's don't come with much of a manual at all. Others don't make it very obvious how to setup non standard configurations. I expect that you will in effect be setting the VFD up as if the motor is rated 240V, 29Hz, and full load current approx equal to 2/3 of the FLC at 415V and don't forget to define the number of poles. Once these settings are locked in, you need to set the motor maximum speed which I'd expect to be on another parameter to go past 29Hz and achieve full speed but at reduced torque.

This is similar in some respects to setting up a 4 pole motor which gives full power at 1400rpm and then defining a higher maximum frequency of 100Hz so that you can spin it up to 2800 rpm (the speed of a 2 pole) but at reduced torque.

If this all makes sense, great. If not, get some help. Frying a new VFD is a waste of money and frying yourself is a bigger waste

Hi Sideways

Please could you elaborate a bit more on that third para? I've set it up...and it runs, but slower than 2/3 speed and with quite a loss of torque. Just feels like the power is attenuated. You're right that the manual isn't much help! I have the same drive on my planer but that had the star/delta option.

I can set a "Reference frequency" - should that be 29Hz rather than 50Hz? There are also "Torque compensation" options - a voltage and a multiplier. I assume "Revolution for 50Hz" is 1425 (it's 4 pole) - I don't see a setting for poles.

Thanks again for your help