Inverter Voltages

I need to run a 3phase motor to power a milling machine.

The plate on the motor states that it is a Brook 1.5kw, 3ph motor, 1420rpm, 220/330 - 420v motor and there is a Delta and a Star symbol stamped in.

Is there any advantage in going for one of the higher voltages or am I best, from a cost point of view, of staying with 220v?.

I do not wish to control the motors speed, just to get it to run the mill.

(almost) Any advice welcome.

Brian

How are you planning to get the three phase? I'd be inclined to run it as a delta wired motor with the more commonly available (and thus cheaper) VFD.

Brian H

As Brian O says using the 220 V delta connection is normal practice when using inverters to run three pahse motors from single phase mains.

As you only plan to run the motor at nameplate speed and don't need the variable speed capability seriously consider the Eaton DE 1 series inverters as supplied by Inverter Drive Supermarket and others. These are intended to be an electronic replacement for the old fashioned electromagnetic contactor that can be installed by any competent electrician. They do have variable speed capabilites but, with no display, this is mostly intended to for simple switching between fixed speeds.

See **LINK** for the 1.5 kw version. Inverter Drive Supermarket offer it at around £115 (+VAT) which isn't unreasonable for a proper UK sourced inverter with back-up if needed. Inverter Drive Supermarket have a justly earned reputation for excellent technical advice and back up.

I have one of those Eaton DE1 boxes running my car lift. Does exactly what it says on the tin and was very easy to install. No need to futz about with a parameters et al. Just power in, power out and off it went using the standard internal settings. I've installed several inverters over the years and can deal with the parameters, setting up and so on with no great worries. But the Eaton was so easy I thought I'm misunderstood the book.

Clive

Edited By Clive Foster on 26/09/2019 21:07:36

If you already have three phase, it will be 415V and the motor will be wired in star. If you don't have three phase and want to run a three phase motor from domestic 230V, then a suitable VFD which has 230V output in three phases will require your motor to be set to delta. The advantage of a VFD is that you can adjust the motor speed.

I am in the last stages of doing exactly that. I have a six pole motor which runs at 935 rpm @ 50 Hz and the inverter will be set to run the motor between 25 Hz and 75 Hz, which is from 467 rpm to 1870 rpm. This gives the mill which only has four speeds by belt, a much improved range of speeds. The motor could be run at lower speeds, but the power drops off quickly, as even at 25 Hz half of the power is lost.

Edited By old mart on 26/09/2019 21:12:38

I have a Transwave static inverter that happily runs my 3HP lathe but would not run my Bridgeport mill for more than 5 minutes at a time. I never did get to find out why. The mill now runs from a HuanYang VFD and has done reliably for 6 years or more. I had a friend wire the VFD as he understands the "Chinglish" in the instructions.

You will be out of luck with the 1870 @75Hz! It will either be 1400rpm or you will need to run the motor @ 100Hz.

Many thanks for the replies; what is the collective opinion of this? (only picked because it is the cheapest!)

And how difficult is the wiring, just to make the motor run without bothering about speed control?

https://www.ebay.co.uk/itm/1-5KW-AC-220V-Variable-Frequency-Drive-Inverter-VFD-Speed-Controller-For-3-Phase/183904336040?epid=12027241491&hash=item2ad18d78a8:g:kM4AAOSwnj5c4lv5

Brian

It looks no different than some others at £20 less money and able to make an offer of a little less.

Last couple I have bought looked a bit like this. Different case sizes, different programming, but both have so far worked OK.

pwAAOSwFcxdU7HY">Cheapo

I think the last one came from Germany or Portsmouth (but delivered from Germany). Cheap, cheerful (no decent motor overload protection, as I recall), but the machines are not left running unattended, so no big deal for me.

They have a ‘wander’ control panel (extension ribbon cables available from the net) so the operating panel can be moved from the installation site to a limited degree.

Wiring is simple, programming is an art-form! Three cores from the supply (13A three pin plug) and 4 cores (possibly with a screening sheath) to the motor.

Right you are, ndiy, my maths was not up to scratch yesterday.

Just as well, I don't want more than 3500 rpm in top gear, the drill mill we use normally only does 2100 rpm.

Edited By old mart on 27/09/2019 16:26:22

Brian H

Cheapest on E-Bay could be anything from bargain of the century through magic smoke comes out to eyes lit up when I touched it.

These days China Inc has completely mucked up everyones perception of price / performance / quality ratios. And, in many cases, the reality too.

Personally I'd not touch it with a barge, let alone the pole. A supplier with no evidence of technical knowledge selling an unbranded box from with the potential for "programming is an art form" to a first time purchaser sounds like a good recipe for serious frustration at best. Downside doesn't seem worth the £70 odd saving over buying a proper known brand industrial rated box from a technically able supplier.

Sounding like a stuck record I know but Inverter Drive Supermarket do some truly superb quick set up guides for many of the more economically priced VFD boxes they sell. The ones ordinary folk like us are likely to buy.

The Eaton DE1 I like is unbelievably (to folk who remember how things used to be) easy to install. See commissioning halfway down this link **LINK** basically add wire and two push button switches and you are good to go. Frankly I'm surprised that they don't supply an offical button box with two switches and numbered terminals as an official extra.

Clive

Edited By Clive Foster on 27/09/2019 19:48:27

I bought both the motor and the VFD from the Inverter Drive Supermarket, and studied their "quick start" pdf's before buying. This was to ensure easy wiring, and remote buttons and speed control potentiometer. Be advised, their prices are ex vat.

 Some of the vfd's that they sell do have the option of a fully equipped remote switch box.

Edited By old mart on 27/09/2019 20:36:24

Hi you can try Drives Direct Kirkby in Ashfield www.drivesdirect.co.uk down from Kirkby cross towards Pinxton.

David

A VFD will be able to supply the motor with what it needs, the rest of the controls will need to be adapted to control the VFD. As you say you are not requiring the variable speed feature then you may find that a better solution would be a Transwave style converter which you could just plug the whole machine into and not need to do anymore.

Mike

Edited By Mike Poole on 27/09/2019 23:43:34

The soft start option with a VFD is, I feel, a worthwhile feature to merit it over the old converter route, for supplying a 3 phase supply from a single phase supply. That is without the electronic protection provided by the higher quality/more sophisticated VFDs. Only a small stand-by current and silent, when not powering the drive, (compared to the rotary converters) may be further advantages.

The older technology might be a cheaper purchase for a 415V motor which cannot be converted to run on 220V delta connection.