Question
The line boring machine that I bought is a Detel MV-23P. It is 3hp and 3 phase. I only have single phase power so I need a phase converter and don't know anything at all about them. I don't know what is involved with hooking one up or how big of one to buy. To my understanding you plug a 3 phase motor into the converter and the converter cord into the single phase outlet? I've been looking at some that Grizzly has, but I honestly don't have a clue what I'm looking at. Any help is appreciated.
Forum Responses
(Cabinetmaking Forum)
From contributor L:
I made a homemade rotary converter a long time ago. It worked fine for several years until I moved to a shop space with 3 phase. From what little I know about them I'd get a rotary as opposed to a static (electronic).
A rotary converter uses the single phase 220v input to spin a 3-phase motor that is incorporated into its construction. Just like with the static converter it runs on single phase 220v. However since it is a 3-phase motor the third leg is actually generating power, somewhat like when a generator is running. This third leg is sent to your machine motor along with the 220v that is in your building. Now you have 3 power legs going to your 3-phase machine motor so you have full power. The trick here is to get all three legs balanced in terms of voltage and current draw. In some situations you have to be careful which input terminal on your machine receives that "manufactured" third power leg or the machine won't work properly or at all.
Those are the basics. If you need the full power rating of your line boring machine then you need to go with a rotary converter. If the machine is overpowered for what you are doing then you can get by with the lower HP output you'll get with the static converter. Static converters are much less expensive than rotary converters.
There is one more possibility. I know nothing about line boring machines but if there is a variable speed option on the machine then it might have a variable speed motor. AC motors do not do variable speed (at least economically). Instead they use frequency drives (also called inverters) to adjust the motor speed. Some frequency drives will input single phase and output 3-phase variable speed to the motor. These in effect have static inverter circuitry incorporated into them. So, if your line boring machine has a variable speed option you should look into these specs. They should be listed in the machine manual.
Be sure to allow for eventual machinery exchanges as you will undoubtedly want to do and do locate your converter right next to the main panel rather than running start-up wires some distant away. These things all require a significant kick start.
Coincidentally we were on the phone just this morning talking about frequency drives. I knew they generally operated as AC in, DC in the middle and AC out. However I thought they were like static converters and the output was 2/3 of the motor's rated horsepower if you were inputting single phase.
After five minutes of his explanations about the only things I followed were first that I was wrong about them outputting only 2/3 of a motor's power, and second that the AC to DC and back to AC was generally correct but not operating anything like I thought.
It turns out the power output has nothing to do with the single phase input. If you think of it in terms of wire size and current draw the single phase input wires need to be sized to the full motor power as if it were running on single phase and the 3-phase output is sized to the 3-phase motor requirements. That is your wire TO the frequency drive will be larger than the wires FROM the frequency drive to the motor. This of course applies to frequency drives that are run from a single phase input as vs. those that input from 3-phase.
On the current type I thought the DC in the center of the circuit was there to allow for a variable speed output controlled in the DC circuitry and then converted back to AC on the 3-phase output side. It would seem this is not what is happening and he totally lost me with his explanation of what is actually going on.
