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Discuss Single to three phase converter in the Electrical Tools and Products area at ElectriciansForums.net

SJD

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One of my customers has a single phase to three phase converter, to power a 3-phase pump. The converter is a rotary type, quite noisy, and recently has been prone to breaking down (three times so far this year).

So they are looking for a static or "digital" converter replacement, 230V to 400V. The existing rotary converter is rated at 6kW. I don't have the motor type plate info at this time, it is not very accessible (it is in a sewage tank).

An internet search brings up a few suggestions, but frankly some of them look a bit rough, like they are built out of spare parts in someone's garage. Does anyone have any recommendations such a converter - brand or supplier?
 

Marvo

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Staff member
Easiest would be a VFD but most of the single to 3-phase VFD type converters are 230v in and 230v phase to phase out so the pump would need to be able to run in 230v star configuration for it to be compatible.

I see the existing converter is 6kw, what is the kilowatt rating of the pump? I don't think the single to 3-phase VFD's go much above 1.5 or 2 kw from memory.
 

Marvo

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Staff member
I've used the Danfoss Vacon for small drive applications range quite a lot recently, they're reliable, pretty straight forward and the price is very reasonable.

I just checked in the catalogue and here's a link to the largest single to 3 phase offering which is 2.2kw.
Vacon 20 2.2kW 230V 1ph to 3ph - AC Inverter Drive Speed Controller - AC Inverter Drives (230V) - https://inverterdrive.com/group/AC-Inverter-Drives-230V/VACON0020-1L-0009-2-EMC2-QPES/

There's a user manual you can download from there which will give you better details.
 

SJD

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  • #4
Easiest would be a VFD but most of the single to 3-phase VFD type converters are 230v in and 230v phase to phase out so the pump would need to be able to run in 230v star configuration for it to be compatible.

I see the existing converter is 6kw, what is the kilowatt rating of the pump? I don't think the single to 3-phase VFD's go much above 1.5 or 2 kw from memory.
I don't know the pump rating, other than this 6kW converter was specified when it was installed. Unfortunately it is sited somewhere unpleasant and not easily inspected. The customer doesn't have the pump details but should be able to get them from the company that supplied the waste system.

The pump cannot be configured. The waste system is moderately new and still under warranty as a whole (tanks, pump, plumbing, etc.) and the customer does not want to risk that by changing or reconfiguring the pump. It was all ordered before it was decided the site wasn't actually getting a 3-phase supply after all (which would have been costly to install), hence the converter.
 

Marvo

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Staff member
The only other option I can think of is to buy three Victron Multiplus units, supply them all from the single phase supply and link them together in configuration to give a 3-phase output. They will give a 400v phase to phase output so no reconfiguration of the existing pump would be necessary.

Probably not a cheap solution but it would allow for back-up batteries and solar panels to be added which would give power outage protection and possibly reduce running costs over time.

I've set up a system like this several years ago and it worked well (still does). The kit has probably changed somewhat since then so maybe post in the Solar Forum for more info if you think it might work for you. The Solar PV guys will probably have some experience with the Victron setup.
 

Lucien Nunes

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Esteemed Member
Does the converter power only the pump motor, or a complete integrated system of pump(s) and control panel? If it's just the motor, the quest would be for a single-phase input, 3-phase output inverter drive or VFD, that operates the pump under the control of the panel. If the system as a whole takes 3-phase input, then a continuously running converter that outputs a steady 400V 50Hz, that functions correctly with almost zero load is required, which is a different animal.
 

SJD

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  • #7
Does the converter power only the pump motor, or a complete integrated system of pump(s) and control panel? If it's just the motor, the quest would be for a single-phase input, 3-phase output inverter drive or VFD, that operates the pump under the control of the panel. If the system as a whole takes 3-phase input, then a continuously running converter that outputs a steady 400V 50Hz, that functions correctly with almost zero load is required, which is a different animal.
The 3-phase supplies the system, which includes level sensors, so that the pump starts/stops as required according to tank levels. So the converter has to operate under a minimal load and full load.
 

SJD

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  • #8
The only other option I can think of is to buy three Victron Multiplus units, supply them all from the single phase supply and link them together in configuration to give a 3-phase output. They will give a 400v phase to phase output so no reconfiguration of the existing pump would be necessary.

Probably not a cheap solution but it would allow for back-up batteries and solar panels to be added which would give power outage protection and possibly reduce running costs over time.
Costs are an issue, and I don't think there would be any interest in backup batteries etc. If the system fails, someone rings up for a tanker to call by, pump out the waste and take it away!
 

SJD

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  • #10
@David, no there is a small control panel only, nothing like your photo. It is a commercial premises, not houses, but just doesn't happen to have 3-phase power.

Since the earlier posts, the customer managed to get hold of the pump info (as I said before, it is sited somewhere unpleasant) and it turns out the original rotary converter was sized to be able to power both the main pump and a backup pump at the same time.

Only one pump is ever used at a time (the backup is rarely used) and the converter could be half the size, so long as we make sure both can't be turned on at the same time.

The customer is considering a static converter from Motorun.
 

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