Author Topic: Driving 3 phase pump from single phase inverter  (Read 2912 times)

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Offline frackers

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Driving 3 phase pump from single phase inverter
« on: July 24, 2016, 12:51:06 am »
Greetings all

Back from holidays so getting back into the Ozinverter and associated stuff.

Far as I can see I can use a Variable Frequency Drive to operate my 4hp (3kw) 3 phase well pump from the Ozinverter.

The power requirements are fine and they usually specify 1 or 3 phase input and 3 phase out but not sure what voltage spec I should be ordering though as I'm seeing both 220v  and 380v devices. I'm guessing that the 380v items require 3 phase input to keep the input current down!

Where a VFD is quoted as 220v to 380v, they are usually cost 50% more - like this one
http://www.aliexpress.com/item/5-5KW-Input-Voltage-220V-Output-Voltage-380V-Spindle-Inverters-HUANYANG-VFD-Drive-AC-drive-frequency/900251508.html
compared to this one
http://www.aliexpress.com/item/New-Huanyang-5-5KW-220V-AC-vector-control-inverter-variable-frequency-drive/32701410282.html

Can someone shed light on this?






Robin Down Under (or are you Up Over!)

Offline Pete

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Re: Driving 3 phase pump from single phase inverter
« Reply #1 on: July 24, 2016, 02:21:51 am »
Hi Frackers , looking at the VFDs that you posted links to yep they do have different output voltages. Now not many motors in Australia will run on 220 volt 3 phase.
There are some that are designed to be run on 220 volt in Delta and 380 in Star but of course you would have to get one of those.
If your motor is now connected in Star you could just get the 220 volt unit and reconnect the motor in Delta.
If it is already in Delta then you need the 380 volt VFD.
Hopefully yours is in Star at the moment, it should be written on the nameplate what voltages it runs on.
Cheerio
Pete

Offline Pete

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Re: Driving 3 phase pump from single phase inverter
« Reply #2 on: July 24, 2016, 02:48:11 am »
Hi again Frackers. I just remembered that years ago I did get a 3 phase motor to run on single phase by hanging a capacitor across one winding. Then another capacitor with a switch across the other one. The motor is connected in Delta for that configuration. From memory you lose a bit of power but then it depends on how much you actually need.
Other than that a friend was playing around with rotary converters, basically a system of using a 3 phase motor as a static generator. Not sure of the efficiencies of them but there are commercial models around. Their advantages are that they produce a proper sine wave and there is no need to bother with all the electronics.
There are probably videos on You tube but definitely articles on the web about both systems.
Good luck
Pete

Offline oztules

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Re: Driving 3 phase pump from single phase inverter
« Reply #3 on: July 24, 2016, 06:41:33 am »
I use VFD on one of the inverters used for salt water RO on an off shore island... 240v in 240v out.

I agree with pete on most of it, but I find there are more motors in star 415v here than delta which is good for me as I run  rotary a  inverter here for the mill and brake press etc in the work shop. ( 10 hp motor with 700uf start and 50 uf on the phases for run ( I think..)... been 12 years since I looked at it, but use it near every day..... and I have stolen some of them and not replaced em later on so it was 1500uf originally).... uses the third phase winding to sense voltage to control the start switching relay.

So it will run any vfd you choose..... and you can always wind a small 10A 415v winding on the torroid as well for 415v operation... ;).... well you have done near everything else with it... why not that??


Easiest to just look for star 415v motor and rewire to delta.... and run 240:240 vfd, they are so cheap now.

The voltage is not terribly important 380-415 no biggie as speed is a hertz problem, not a voltage problem, you will only loose a bit of torque
... which you can dial away anyhow.

380v or 415v inputs  use less current not more, for the same power than 240v, so better chance for single phase to run it.... but rally it is only the bridge input that will make any difference at all.. 4 diodes or 6 carrying the load ( single or 3ph inputs).. after the rectifier there is no difference.

I run up to 4kw in single 240v for water pumps on farms here, usually 3ph 415 for 5kw and over.

A vfd with 5-10 second ramp will do very nicely for the inverter.

............oztules
Flinders Island...... Australia

Offline frackers

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Re: Driving 3 phase pump from single phase inverter
« Reply #4 on: July 24, 2016, 07:03:03 pm »

Easiest to just look for star 415v motor and rewire to delta.... and run 240:240 vfd, they are so cheap now.


The motor is wired for delta (i.e. there are 4 wires - 3 phases + ground going down the hole) so its already 415v (at least that is the way I would spec a delta connected device - phase to phase voltage). I'll not be changing it as I've had a replacement 4 years ago and that was $2k with the crane to lift the 55m of pipe out of the ground to change it!!

Looks like I'll be going for the more expensive type of VFD that can handle the input current current on a single phase 240v and then using a 3 phase bridge to get the 415 out - at least that is how I assume they work!!
Robin Down Under (or are you Up Over!)

Offline oztules

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Re: Driving 3 phase pump from single phase inverter
« Reply #5 on: July 24, 2016, 10:40:24 pm »
No Frackers, going down the hole you will normally ... actually always use 3 wires at 415 and an earth.... it depends on how they wired up the stator fields.

If they use two phases in series, then star 415v config, if they use a single coil group in phase across the mains, then delta 415v.

But see your point, access is the problem.

In a normal unit, there will be 6 terminals in the terminal box, and we star/delta there.


.........oztules
Flinders Island...... Australia

Offline Pete

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Re: Driving 3 phase pump from single phase inverter
« Reply #6 on: July 25, 2016, 02:24:34 am »
Hi Frackers, well then that sorts it, you will have to go with the 3 phase 380 volt unit. If you only have three wires plus earth going down the well and the motor is in delta already that is it.
Other than that if you only run it a bit then a rotary converter may be one way to go if you make it yourself.
Rotary converters don't seem to have much in them just an induction motor that you should be able to pick up cheap and a couple of other components.
Unless of course you have a three phase transformer that you can use with the 230 volt VFD.
Good luck
Pete