Powering a CNC Router Using a Phase Converter

It works fine, say those who are doing it but there are a few details to consider. November 12, 2005

I am looking into a CNC router option for my shop. Will I run into problems using a phase converter to run the CNC?

Forum Responses
(CNC Forum)
Yup, you can experience brownouts, and low voltage startup. Brownouts are a killer, as the emergency devices run on 110v and the CNC requires 440.

You typically don't want to run your CNC router spindle from a phase converter, but that doesn't mean you can't run a 3-phase CNC spindle on single phase. We have single phase in the shop and run a 10hp HSD 3-phase spindle just fine. The trick is to use a single phase input inverter to run the spindle. These are readily available.

However, if you are going to have a 10hp spindle, then to get full power you'll need a 20hp inverter. On our system, we never push our 10hp spindle past a 5hp demand load. As such, we get by with a 10hp single phase input inverter. I've been running this way for over 2 years on my current router, and did the same with a 7 1/2hp inverter and a 5hp spindle on my previous router.

If you are purchasing a light to medium duty router (Techno Isel, Multicam, CNT Motion, Axys, etc.), then that is your only 3 phase issue. Most of those machines probably only need 3-phase to run the spindle, as the balance of the system runs on 110v or single phase 220v input.

Larger, very heavy duty machines that cost $100k plus might be a different story. I don't know that I would want to get into that class of machine without 3-phase.

Our shop is run completely on phase converters. They include CNC panel saw, router, boring-dowel insertion machine, widebelt sander, dust collection system and bander.

Our shop is also completely run on 3 phase converter. CNC routers, etc. - no problem. Just buy a good converter, as there is a lot of crap out there on the market. Brownouts? Low voltage at startup? Don't know what that is all about, but we have been on a converter for 18 years and never a problem.

We use Arco 150 hp phase converters. Run Komo 16 hp, moulders, CNC panel saws, CNC shape and sand, etc. Never had an outage of any color because of it. The main thing you must remember is that the generated leg will always produce higher voltage in an unloaded state. This leg should never go to the control side of equipment! Also, this will throw the 120 degree phased out unloaded.

From the original questioner:
Thank you. Is 200 amp service line enough to run a converter for one CNC router such as Komo or Hein, an edgebander, a panel router, a line boring machine, a dowel machine, and dust collection?

Just need to add up the amp load and see. Should not be more than 80% of nameplate amp draw. Call Arco Electric, Shelbyville, Indiana. They have been very helpful to us over the years in our power needs. Arco's Roto-Phase converters are the top in the industry. They make many different converters for CNC machines. We have converters that have run every work day for 21 years.

We have 3 phase power about 2000 ft. from our shop and the power company wants about $70k a mile to run the lines, plus to put us on a demand meter.

We got estimates for our 3 phase service just down the road at $40K plus demand. I have just bought my second phase converter in 18 years. We worked with Kay Industries, the Phasemaster people, on our latest purchase. They were recommended by our CNC manufacturer, Multicam. Very good unit so far. Be aware that there is a lot of crap out there on the market. ARCO and Kay have been around for a long time. Shop wisely. We also have a 200 amp service and run with no problem. With only a 5 man shop, we never have all equipment running at the same time.

My shop is all phase converters as well, with CNC equipment. Try Gen Tec - they make a CNC balanced converter. I also recommend running the CNC on a dedicated converter (no other machines hooked up). That way you will not experience any voltage drop if other machines are starting up. It is mainly for the stability of the voltage to the computer and inverter.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor J:
We run most of our equipment on phase converters. The biggest problem with phase converters is that they are only 78% efficient, meaning you pay 22% in your electrical bill and get nothing for it. We just switched to an VFD (variable frequency drive) and this will provide the third leg needed for your 3 phase machinery. The VFD is 98% efficient, and when your machinery is not running the VFD is not running.

Comment from contributor A:
Phase Converters work great - just be sure you get one large enough without overloading it. We have been using Desco Phase Converters for years on our CNC equipment without a problem, so phase converters will do the job.