Question
I am trying to find a site to set up an electric sawmill and was wondering if electricity that comes through a phase converter is the same as straight 3-Phase electricity.
Will I have the same power?
Will there be any adverse effects on the motor?
Will it cost more or less to run?
Forum Responses
I have had good service out of the static converters I purchased from Gerhard Werner Motor Werke. They are very eager to help. The information they gave me was straight forward and easy to follow. I don't have experience with the larger rotary units they sell. But I do know if the rotary unit is sized correctly and the hard to start motors on the system balanced with boosting capacitors, everything will be equal with power company service.
The expense is the thing to deal with, not the lack of technology. Their lower priced products may be seen in Grizzly catalogs. They also make custom systems to order.
I have a rotary phase convertor that is rated to start a 5 hp motor which is under load, and 15 hp total once each motor is started, i.e. it will run any number of motors up to a total of 15 hp as long as you don't exceed the load of a 5 hp motor on each startup. However, I can easily start and run my 7 1/2 hp tablesaw even though it exceeds the 5 hp startup rating. The reason for this is that a tablesaw motor starts under a very low load and is only taxed for a short duration.
Three phase motors draw higher amperages to start and when under load than when running under little or no load. A rotary phase converter is a good investment if you are running multiple machines or the cost of replacing a 3 phase motor with a 1 phase is prohibitive. The big advantage is that 3 phase motors are cheaper to buy, require less maintanence and are more efficient to run.
From the original questioner:
I'm looking at a 25-30 HP 3-phase electric mill with possible additions of a 15 HP 3-phase edger, a dust collection system, etc.
What is a genset?
Another thing about generator sets is that when they go belly up you are all done working until you get it fixed or rent another. Commercial power is quite reliable. I know this can happen as a friend of mine had his genset go south and he was down for just about a month.
Comment from contributor A:
You should have seen the first phase converter I built. I had pulleys, ropes, pony motors all over the floor, not to mention the switches and wires and capacitors that took up about half my garage, but it worked and I was proud.
It all started when I bought a lathe and was in the same quandry that you guys are in. I met an old man who knew how to make a backyard converter and that got me interested - so much that I sold the lathe with its converter and started building phase converters for all of my friends. As I got better and better, the converters got better and smaller. The biggest one so far was a 40 hp for a man who had a wood shop, and maybe 4 15s and about 12 10s, but as far as the 5hps and 3hps, I lost count how many I have built in the last 15 years.
All I know is that once you get fascinated, it's easy. Now I have the capacitors and stuff shipped UPS and I have a lot of testing meters and tools that make it easy, no guessing.
Can a converter deliver the same exact 3 phase as the power company? No, but if you take your time putting the right amount of capacitors between line 1 and line 3 and also between line 2 and line 3, you can get it so close that your motor won't know the difference. Some converters that you buy will have 3 phases alright, but the voltage will be 240--223--216 and guess what, the motor runs just fine. The only bad thing is when you work the motor hard, it gets hot. My converters 3 phases will read 240--239--241 or so, because I take my time.
How long will a converter last? Forever.
Is it cheaper than 3 phase from the power company? Yes. I won't even mention the cost of having it brought to you, because even if 3 phase was right there, it would be cheaper for you to have a well-tuned phase converter. If you have a dozen large 10 - 15hp machines, that's different, but the people that I build converters for are much better off investing in a lifetime tool that they can take with them.
