3 phase inverters – static vs digital

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3 phase inverters – static vs digital

This topic has 19 replies, 5 voices, and was last updated 20 February 2012 at 22:22 by MAC.

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4 February 2012 at 22:32 #83886
MAC
Participant
@mac53652
Hello,

Following on from my mill transportation thread (the seller is now delivering the mill for the cost of fuel – which is a nice solution as it was a bit of a worry), I’d like some advice please on 3 phase converters.

The mill has a separate power feed motor (plus a lamp and coolant pump), and I would like to literally plug the machine into a converter as though it was being connected to a genuine 3 phase supply. I believe I can do this with a static converter, such as the Transwave unit.

I realise this will make me miss out on benefits such as soft start and variable speed, which would be great to have – but I’d rather avoid such things as altering the internal wiring of the machine and making the original switchgear redundant.

I’ve read up the best I can but there are conflicting reports out there. Drives Direct sell a 240V – 415V unit, would this enable the entire machine to be plugged in to the digital inverter, rather than the motor alone? The diagram they show suggests not, but their blurb suggests otherwise. It’s very confusing!

Obviously I can’t tell at the moment if the motor can be reconfigured star/delta, given the age of the machine I doubt it (unless it’s on a replacement motor already) – which leads me to the third option………which is replacing the main motor with a single phase one, which again isn’t something I want to do ideally.

Many thanks,

Mike.
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4 February 2012 at 22:32 #11885
MAC
Participant
@mac53652
5 February 2012 at 18:06 #83963
Nick Hopwood
Participant
@nickhopwood71702
Hi

I run a mill with coolant and table feed using a static converter. It is necessary to wire it so that the coolant and table feed only run with the main motor running so that the converter does not harm the smaller motors. With the main motor running the converter becomes a rotary converter and the smaller motors are ok. I don’t think it is feasable to run the lighting transformer at the same time as it would turn off when the main motor is stopped. I have connected mine to the mains as it only uses one phase from the normal three phases and it seems to work fine.

Cheers

Nick
5 February 2012 at 18:51 #83964
MAC
Participant
@mac53652
Thanks Nick.

How did you go about interlocking the power feed and coolant pump?

As you say, the lamp is easy enough to sort out.

May I ask what made you choose a static converter instead of a digital?

Cheers.

Mike.
5 February 2012 at 21:47 #83994
Jon
Participant
@jon
Static not exactly load tolerant.

Likewise i have a Transwave convertor think its 5kw running a 3ph 3hp motor in plug and play as machine was intended for. Its easy to slow the spindle down putting a mild cut on, even worse with Statics.

For a similar price as Transwave 7.5kw you can have the MA7200 digi 240V single ph input to a proper 3ph 400V outputs, which means exactly the same plug and play. Thats how mine runs, power on at switch, hit run then hit the lever start. I can plug any 3ph equipment in to the hard wired plug.

I know they have an MA7200 4kw? factory refurbed going cheap.

Rotary convertors ok but big and heavy, what annoys me is the noise, cant hear yourself think. Kept as a backup.
5 February 2012 at 22:07 #83999
MAC
Participant
@mac53652
Hi Jon,

Thanks for info.

Is this 7.5kW unit you mention the inverter I’ve seen sell for nearly £1000? If so, it’s way over what I can afford at the minute.

That does look like the ideal thing for me though, but I think I’ll have to compromise and get a static.

I suppose I could contact Transwave and ask about this 4kW no harm in asking.

Cheers,

Mike.
6 February 2012 at 14:43 #84036
Jon
Participant
@jon
What do you intend to power up in KW, you will need above the total motor power same as with a digi inverter.

Know of an MA7200 approx £500 at Selston, think its the 5/5.5hp 4KW 240v single phase in, 3ph 400+V outputs.

I have the MA7200 7.5KW after one of the above inverters was not man enough for my lathe, cant get spindle to slow with 1/2″ cut whereas Transwave 4KW? might be more below limited to 1/8″ and serious groans.

Likewise above 4KW inverter with 3hp motor (2.2KW) you can get spindle to slow with around 1/4″ cut. All fed from same power supply.

Think a rotary Transwave 4KW s/h would knock you £300 to £350, believe me they are massive and heavy with a lifting eye attached to motor. We wont mention the noise, got good neighbours, that bad!

Statics are frowned upon dont ask the above two companies

Ideally you need to at least double even approach three times the motor capacity unless wired to motor. I learnt the hard way cost me a wasted £650 for 1 1/2hrs use. Killed me to fork out £1100 for 7.5kw. Had i have known from the start , it would have been cheaper to buy another 3ph 3hp motor and a conventional 3ph 220V output inverter, but the hassle of sorting the wiring with no help from sellers.

Where abouts are you Mike?
6 February 2012 at 18:36 #84053
MAC
Participant
@mac53652
Hi Jon,

The motor is 1hp – but I don’t have the machine here yet. Part of the reason I wanted some form of plug and play inverter was so that I could see the mill working before the seller left. The original user used a static, and this last user used a static before moving to a workshop with a 3 phase supply, so I can’t see any major problem. My main reason for wanting a digital unit was the variable speed and soft start.

I imagine the MA7200 4kW you mention would be ideal, but it’s more than I wanted to pay really. I’d more or less decided on a static which worked out at around £270, if it was £350 I’d probably have it.

I never tax my machines, so not being able to run at full beans will never be an issue – if it’s that simple. Rotary inverters have never really been on the list for me.

If I got a static, it would be supplied by one of the above companies – from their eBay shop. Are you saying they’re selling products they don’t approve of?

I agree with you that in the longterm it would be best to re-motor.

I am in Lancashire.

Many thanks,

Mike.
6 February 2012 at 18:41 #84055
Nick Hopwood
Participant
@nickhopwood71702
Hi Mike

I went for the converter because I wanted to run a lathe, mill and surface grinder and at the time I thought I would need an inverter for each of them plus the coolant pumps and mill table feed. I don’t know if that is the case but I certainly couldn’t afford to do that. As far as I was concerned the only answer was a second hand converter or change the motors. Inverters seem to be very expensive for the large ones. My mill and lathe both have 2hp motors and the surface grinder is 3hp. My converter is 5.5kw and runs them all (seperately) without problems although my lathe does not like going up to full speed, especially in cold weather.

Nick
7 February 2012 at 01:23 #84089
Jon
Participant
@jon
If you do go for a static make sure the cooant and power feed are rewired to come on with main motor.

Unused motors have a habit of burning out with statics.

Also think 1.5kw/2hp might be a bit too tight for comfort.

Tell me about it Nick, i thought i was gonna get lathe up and running for £340 with pod, turned out no dual voltage motor and got a refund.
8 February 2012 at 20:47 #84198
frank brown
Participant
@frankbrown22225
I bought a mill with a non functioning static converter ?(burn’t out contactor coil). Once fixed it would not run the mill on hi-speed (2.2 KW) and the motor smelt hot on low-speed (1.5 KW). So I dived in. By selecting the run capacitors I got the low speed working on a much better (and lower) current match. Totally re-jigged the hi-sped circuitry – new start cap and new run caps, which mean’t a second start contactor. It was all working beautifully, now the hi-speed bits gone AWOL. By now I think you might have guessed, I am not a fan of static converters, they need tuning for specific motors.

If you look at the circuit of a rotary converter,its the same as static converter with a motor on it. So what should I do???

Frank
8 February 2012 at 23:11 #84208
Jon
Participant
@jon
If you were local you could have borrowed my Rotary convertor, sure its the 5.5hp jobby.
8 February 2012 at 23:16 #84209
MAC
Participant
@mac53652
Hi.

Thanks for replies.

I might just ask about the digital plug and play – but fear it’s out of my budget.

That would have been very kind Jon, but I’d crossed rotary off my list as I’ve read they’re noisy. Which leaves the old favourite (static)! Seems a lot of money to spend given the negative views though.

Will sleep on it.

Cheers,

Mike.

Edited By MAC on 08/02/2012 23:17:20
9 February 2012 at 08:37 #84213
Swarf Maker
Participant
@swarfmaker85383
Don’t get too hung up about the noise of a rotary – it’s only the sound of a motor! Take some steps to prevent vibration transmitting to the floor and provide a bit of acoustic baffling. You can always seperate the electical box from the motor and put the motor outside of the workshop – suitably protected of course.
9 February 2012 at 20:56 #84267
Jon
Participant
@jon
If i put mine outside in a box the neighbours would complain, the council would soon be round.

Admitedly mine was on a concrete floor but no joke couldnt hear yourself think. Couldnt hear what was going on with the geared head lathe, drounded out the DAB radio on very very loud.

As noisy as a 3hp compressor putting a cut on.

Exactly the same as this 230740255611 on that site.
11 February 2012 at 20:17 #84465
Swarf Maker
Participant
@swarfmaker85383
Well, I’m not pretending that they are quiet but my rotary is the same as the one you have/had. My motor has been seperated from the control box as the box amplified the noise, and sits on a piece of construction (high density) foam. However, it is still inside the workshop sat alongside the Colchester Master 2500, and also powers the Centec and Beaver mills. The (portable) radio is perfectly audible when these machines are running and when I have visitors in the workshop, conversation is not a problem.

Clearly, we have different experience in this regard so perhaps I am particularly lucky in having a quiet motor!
19 February 2012 at 22:53 #85288
MAC
Participant
@mac53652
Hi All.

I thought it was only right to conclude this thread now that I'm up and running.

After all the kind and helpful advice, I narrowed my options down to a "Plug and Play" digital and a static. I couldn't stretch to the digital option, as nice as it would have been – I want to fit the mill out with DRO too so there's a limit I want invested in the machine.

I bought a static converter and it works perfectly. Would recommend them – not sure if we're allowed to mention suppliers on here or not, but the firm I bought from are a sponsor – and also have a shop on the famous auction website we all love to hate (or is it hate to love?).

Thanks again,

Mike.
20 February 2012 at 01:15 #85296
Jon
Participant
@jon
Glad your sorted, just take note of coolant pump mentioned above. A mate uses a 3kw daily but pump disconnected.

Let us know what happens when you put a cut on

DRO are a nice adition when mounted rigid. I wouldnt be without all three of mine. The cheap Sino will require periodic cleaning and a bit of a pain to do with the 45 degree flat glass you cant get at to clean. Swapping two of the three on larger mill for the magnetic i use on the lathe.
20 February 2012 at 09:17 #85303
Nick Hopwood
Participant
@nickhopwood71702
Hi Mike

Glad you are sorted. I've been very happy with my static but I have just seen a 2hp digital from our chinese friends at a very reasonable price (£99.99) which I have bought to try on my lathe. If I used the coolant on the lathe I wouldn't have bothered as it would cause problems trying to sort. Just remember if you do use other small motors like the coolant pump make sure the main motor is running.

Nick
20 February 2012 at 22:22 #85366
MAC
Participant
@mac53652
Hi both,

The machine has actually had its wiring updated at some point fairly recently – and as such the suds pump and power feed motor can't be operated without the main motor running. But on top of this I already automatically turn the feed motor on last and off first.

I agree – DRO is a Godsend, my last mill had 3 axis…….so there's no way I can live without it now! Magnetic ones do look good, although my last were Sino glass and never had a problem.

Good luck with the digital – they certainly do offer many benefits.

Cheers,

Mike.
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