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mikep379
07-18-2009, 11:19 PM
I was wondering if anyone on here has an Acer Ultima 3VS milling machine with a 3hp motor running on a static phase converter, if so what kind? Thanks

SGW
07-19-2009, 10:05 AM
Not an Acer 3hp, but I ran my 1hp Jet mill on a Cedarburg static phase converter for a few years. It worked, sort of, but the lack of power was a problem when drilling large holes and the motor never sounded very happy. Eventually I switched to a VFD. It works SO much better, there is hardly a comparison, and it gives the added benefit of variable speed.

If you're thinking about buying a static phase converter, I'd urge you to find the extra money for a VFD.

gnm109
07-19-2009, 10:10 AM
Not an Acer 3hp, but I ran my 1hp Jet mill on a Cedarburg static phase converter for a few years. It worked, sort of, but the lack of power was a problem when drilling large holes and the motor never sounded very happy. Eventually I switched to a VFD. It works SO much better, there is hardly a comparison, and it gives the added benefit of variable speed.

If you're thinking about buying a static phase converter, I'd urge you to find the extra money for a VFD.


I certainly agree. From what I've read, static converters only provide about 60-65% of the rated power. If you want ful power, you will be needing a Rotary Phase Converter (RPC) or an VFD.

I have a 3hp Webb on an RPC and I get full power.

datsun280zxt
07-19-2009, 11:45 AM
I'm running a 3hp comet on a static converted and have no complaints. I have nothing to compare it to either. I think a lot of it depends on how the mill is being used. I'm working almost entirely with aluminum.

lakeside53
07-19-2009, 12:09 PM
The problems with static converters appears more on lower powered motors than higher. If all you start with is 1hp, and you get a max of 0.6 with static conversion, it's much easier to overload that motor on a machine tool than with 3hp.

Unless protected by a motor starter (as with a direct coupled static converter), little stops a motor from attempting to produce more power then it's rated for. Push the motor hard so it's developing say 1hp again, you've overloaded the active field windings and it will eventually burn out.

I see posts on many boards "the static converter burned out my motor".. well.. not true... the user burned it out by exceeding the capability of the motor to produce power. On a mill you have choices as to the power developed - not so easy with compressors, pumps and other full load devices.

mikep379
07-19-2009, 01:25 PM
I'm running a 3hp comet on a static converted and have no complaints. I have nothing to compare it to either. I think a lot of it depends on how the mill is being used. I'm working almost entirely with aluminum.
Is the motor on the Comet foreign made? What brand and hp rating is the static converter being used?

Uncle O
07-19-2009, 05:20 PM
I used to use a static convertor with my "Modern" Mill.
Tiawan import from the late 80's, looks almost the same as a "Comet",
or a "Birminham" .
Is a 3 HP, used a Phase-a-Matic, 1-3 hp convertor.
I switched over to a rotary model as soon as I got the chance.

mikep379
07-19-2009, 05:38 PM
I am familiar with the Phase A Matic but was also looking at the American Rotary Gentec static converters.Which company would be best to use or does it make any difference? What size of circuit breaker would you use in the breaker box for this application?

lane
07-19-2009, 07:06 PM
I run my Birmingham mill 3 Hp with a 3-5 static and have no problem . Ran my 2 HP Bridgeport on a 1-3 static Never a problem for over 10 years. i have yet to understand what every one is so concerned about. You never are very seldom need full HP any way . Been running all kinds of mills on true 3 phase at work for 40 years and their is no difference.
What they do not tell you Is a foreign made mill 3 HP motor needs is a 3-5 converter NOT a 1-3. Foreign motors pull more amps.

gnm109
07-19-2009, 07:30 PM
The problems with static converters appears more on lower powered motors than higher. If all you start with is 1hp, and you get a max of 0.6 with static conversion, it's much easier to overload that motor on a machine tool than with 3hp.

Unless protected by a motor starter (as with a direct coupled static converter), little stops a motor from attempting to produce more power then it's rated for. Push the motor hard so it's developing say 1hp again, you've overloaded the active field windings and it will eventually burn out.

I see posts on many boards "the static converter burned out my motor".. well.. not true... the user burned it out by exceeding the capability of the motor to produce power. On a mill you have choices as to the power developed - not so easy with compressors, pumps and other full load devices.


So you are saying that a static converter will provide 100% power on a larger motor........that's interesting.

.

lakeside53
07-19-2009, 09:59 PM
It would be interesting, but it's not what I said. The static converter has nothing to do with the load the USER can apply to a motor. A motor does not put out "rated" or "derated" power - it "responds" to the load applied.

What I said (in other words) was that it's easier for the user to overload (i.e. draw more than the rated current though the active windings) a low HP motor that's unable to provide more than 60% (+/-) of it's rated power and stay within its safe operating zone, than a larger motor. The 3 hp motor will still only be safe up to about 1.9-2hp.

You can protect a motor supplied by a static converter with a conventional motor starter - heaters set for the name plate FLA - but few do. An overload on any one one of the legs will trip the supply.

Uncle O
07-20-2009, 09:38 AM
In my case the static box was included with the mill when I bought it.
On the static box it says Full load Single Phase amps 9.6
I'm sure I had a 20 amp breaker and fused down to 15 at the disconnect.
I was using the mill to do work from home and could tell that I was unable to take as much as compared to the machines at work on 3-phase.
I had a DOA rotary given to me and made some repairs to get it running,
and switched over to that.

gnm109
07-20-2009, 12:33 PM
http://www.phase-a-matic.com/StaticDescription.htm

lakeside53
07-20-2009, 12:48 PM
I'm not sure what you are getting at.. but if your are referring to the quote "Using the PHASE-A-MATIC™ Static Converter only will produce approximately 2/3 normal HP." then it's being misread.

A SPC does not produce any power or limit the power to the motor. The motor produces power in response to a load.

Take a fictitious example that isn't 100% accurate, but close enough for explanation. : Load up a mill 1 hp 3 phase motor on a 3 phase supply with a face mill so the current draw is the rated FLA, and your motor is producing 1hp. Put on a static converter and use the same DOC and feed you used before. If the motor doesn't stall it may well produce 1 hp again, but at significantly increased current in the active field windings, which will overheat and likely burn out. Most motors can produce more power than they are "rated" for, but not last. My BP motor is "rated" at 2hp, but as it's built like a tank, it's also rated for 3hp up to 30 minutes. I bet I can pull more than 3 for short periods.

Another example -take a hard working compressor with a 3hp motor. Put on a static converter without changing pulley sizes... see how long it will last (if it's even able to get up to speed). Change the pulley so the required power is say 2hp, the compressor will charge slower but will likely be o.k. Also... If it has the recommended motor starter, it would pop the thermal trips in the first case.

Edit: look like they cover this in the Technical Documentation:

WHAT TYPE CONVERTER SHOULD BE USED?
The most important question for your customer is whether or not the motor is heavily loaded. You must keep in mind that wye-wound motors will produce approximately 2/3* of its rated HP when running on the Static Converter. If the motor is loaded beyond that point, you must use our Rotary Converter or use method Number 2 as explained on our literature. Otherwise you must unload the motor by reducing the motor pulley diameter by 1/3 or increase the horsepower by 50% to accommodate the loss of power.

gnm109
07-20-2009, 08:05 PM
I'm not getting at anything. I posted that to show you where the information came from regarding an SPC producing less than full rated power on a given motor. It is similar to the information posted with other manufacturers of SPC's. The information did not come from me.

Suffice it to say that I certainly won't be buying an SPC. Either an RPC or a VFD would be the best unit for converting single phase to three phase, to use a few acronyms. LOL

Nothng you have said so far convinces me otherwise. I presume everything that you say is correct but it sounds like a semantic issue to me in any case.


Regards. :)

lakeside53
07-20-2009, 10:38 PM
Yes, it may be semantics, but... if that's true.. it just means I'm not expressing myself clearly. And.. I hate to leave things muddied. ;)

Simply... An SPC doesn't produce any power or "limit" the power that a motor may try to consume in response to the load. Taking it one step further, neither does an RPC. Heck, neither does connection to the utility. Add a motor starter with correctly sized thermal limiters (or a more modern electronic version) to any of the above will provide protection.

What I'm really saying in all this technical mumbo-jumbo is that a great way to fry a motor when you knock 40-50% of its capability off...is to be oblivious of the issues outlined.

The other hand, a vfd (if programmed correctly) on has an integral (and often better) equivalent of the motor starter functions to protect the motor. Sadly, I see many installations where the nameplate FLA have not been programmed into the vfd.


Personally.. I'm not a fan of static converters at all. I'll use a VFD as first choice anyday.