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3-phase converters - reliability?

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MusicMan

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I'd like other people's experience on the reliability of 3-phase 415V converters.

I've had three machines set up for 4 - 7 years on DrivesDirect 240v 1p to 415V 3p converters and they have worked very well, including soft start and rapid stop: a Boley metal lathe, an Arboga miller and a Wadkin AGS10 saw. They were expensive, £400+ but the firm was very helpful in setting everything up. They have had relatively light hobby use.

This week I set up quite a complicated cut on the miller, spending a couple of hours aligning it, switched on the miller and - nothing!
Communication with DrivesDirect elicited that 7 years was a pretty good life for a consumer electronics component these days, it was most likely the output unit that was shot, the components were very hard to get and anyway the unit is obsolete. Buy a new one at £400.

I was a bit shocked at this, especially as I have two others of similar life. A new output board at £50 - £100, fair enough. I know the poor electronics does not have the longevity of logic components, hence the poor lifetime of inverters for solar energy systems, but not making the replacement backwards compatible is sinful!

So before I sign the cheque, what is the general experience of reliability of converters, especially the 415V ones? (I can't rewire this particular motor to delta, before you ask, it's all buried). Two of the machines are in the same workshop. Would it be sensible to think of a rotary converter to drive them both (which you can't do with the electronic models, they are one per machine). Are they any more reliable?

Keith
 

Myfordman

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I've been supplying hobbyists with inverters for about the last 15 years and only a couple of problem ones out of 50 or more.
Electronic converters (more accurately inverters) are generally more reliable than static or rotary converters but when they fail it is usually catastrophic. Dave at DD is correct, replacement IGBT modules are very difficult to obtain and usually so deeply embedded that a new unit is the only realistic answer.
Converters, static or rotary suffer from both capacitor and contactor failure but they are much simpler to work on and with sound electric/electronic understanding are simple to fix. You can usually get circuit diagrams for Transwave ones and they are the market leader with good support. I've had one rotary in for repair where the motor had burned out and rewinding was not economic so that was a right-off.
One important advantage with an inverter is the gentle loading imposed on the electrical supply into the workshop. Rotary converters are reasonably gentle but static ones are beasts and you must have a low impedance, overload tolerant supply into the workshop with a type D breaker.
Also static converterswill only give you say 75% of the power from the motor as the third phase is an approximation whereas from and inverter it is near perfect.

Given your experience with inverters, provided you don't need variable speed or controlled acceleration/deceleration then maybe try a rotary - maybe a used one and learn about refurbishing them if needed
 

topchippytom

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I have a transwave converter in my shop and its been faultless up to now but you are talking over two grand for one as its a 15 hp,I moved up from a 5.5hp clark inverter about 18 months ago,What size motor is on the one machine that need a replacement one.
 

deema

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Well, if it were me I would convert the AGS10 by replacing the motor and DOL to a 2.2KW single phase motor. The conversion will cost c£150 for the bits. Don’t ask me why by 2.2KW Motors are cheaper than any other power. A 90L frame will fit perfectly.....with a set of new mounting holes. It will give your saw more umph which is always beneficial. This will also increase the value of your saw and free up an inverter for the Mill.

Just an aside, do you need 415V or have you changed the motors from star to Delta to allow you to buy a far cheaper 1ph to 3ph 240V? An inverter of c 1.2Kw is around £150.
 

MusicMan

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Thanks all for the helpful comments. Very good points about the loading on the power supply, and good food for thought on other matters.

Variable speed is perhaps not essential, but I use it a lot on the miller and lathe. Not on the saw, but I do like the 8s electronic stop. I suppose the miller does have harder use. I use the lathe and saw more often, but rarely for more than minutes or tens of minutes in a day. Whereas when running the miller it is usually going all day.

The miller motor (415V) is well buried inside. I don't think rewiring is realistic without a lot of hassle. Though if starting from new, as I may do with another lathe, it will be a 240V motor.

Keith
 
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