I've had a few folks ask me about this subject, so here's a thread devoted to it!
There are a few ways to power 3-phase tools from a common household single-phase supply... some are simpler than others, some are more expensive, some are more versatile. Each has it's downfalls, as well as strenghths.
In each scenario, you'll need to be very aware of the type of electrical load which the machine presents. this includes the voltage required, the max run current, the start current, the amount of time required for the machine to get up to speed, and wether the machine will be starting under load, or unloaded.
The three most common methods of operating 3-phase machines on single-phase power are:
1) AC drive, or 3-phase inverter. These are commercially-available devices manufactured by a wide variety of suppliers. Typically they are designed to accept 3-phase 60hz in, and generate 3-phase variable-frequency out. Most of these devices can do the same off of single-phase input, albeit at about a 33% derate in performance. They also typically do 'soft starting' operations, dynamic braking, overload protection, and other neat functions. Fancy ones are expensive, while inexpensive ones, with less features, etc., are cheaper. I recently had the opportunity to install and test a very compact 4A output AC drive... the KB Electronics KBVF... on a Bridgeport BRJ 1hp mill, and found it to be an excellent device for the application. Cost of the KBVF used was about $225.
2) Another method is to drive the machine's 3-phase motor off of single phase (connect the two 'hot' wires to two of the motor leads) and use motor run capacitors (from each 'hot' lead, to the remaining motor leg) to 'simulate' the presence of a 3rd phase. In this situation, the run capacitors need to be selected to match the motor HP rating, and capacitance on one leg needs to be higher than the other by about a factor of 2. Also, to get the motor to 'start', either a pony motor needs to be connected (to get it spinning), or a rip-cord wrapped around the motor shaft and pulled (Not reccommended by me), or an additional 'start' capacitance can be temporarily placed across the larger RUN capacitor bank (like... about 7x the larger of the RUN cap banks) to kick the motor in the right direction... once the motor is up to speed, the START caps can be removed, and the motor will continue to run. This is referred to as a 'static converter'.
3) The last method, is to make a 'rotary converter'. The rotary converter is essentially a single-phase to 3-phase transformer... it uses a surplus 3-phase electric motor, rigged up with a 'static converter' (described above) to start and run. Once running, the electric motor's A, B, and C phases will provide 3-phase AC out to operate another tool. To clarify how this works, the 3-phase motor is actually used as a rotating transformer... the motor's windings GENERATE the 3'rd phase. The 180-degree single-phase power is fed across two (120 degrees) of the 3-phase 'idler' motor's windings, and the result is a 3rd phase of power out. In a rotary-converter, the converter's idler-motor must be about 25% larger than the load you plan on running.
There are a few ways to power 3-phase tools from a common household single-phase supply... some are simpler than others, some are more expensive, some are more versatile. Each has it's downfalls, as well as strenghths.
In each scenario, you'll need to be very aware of the type of electrical load which the machine presents. this includes the voltage required, the max run current, the start current, the amount of time required for the machine to get up to speed, and wether the machine will be starting under load, or unloaded.
The three most common methods of operating 3-phase machines on single-phase power are:
1) AC drive, or 3-phase inverter. These are commercially-available devices manufactured by a wide variety of suppliers. Typically they are designed to accept 3-phase 60hz in, and generate 3-phase variable-frequency out. Most of these devices can do the same off of single-phase input, albeit at about a 33% derate in performance. They also typically do 'soft starting' operations, dynamic braking, overload protection, and other neat functions. Fancy ones are expensive, while inexpensive ones, with less features, etc., are cheaper. I recently had the opportunity to install and test a very compact 4A output AC drive... the KB Electronics KBVF... on a Bridgeport BRJ 1hp mill, and found it to be an excellent device for the application. Cost of the KBVF used was about $225.
2) Another method is to drive the machine's 3-phase motor off of single phase (connect the two 'hot' wires to two of the motor leads) and use motor run capacitors (from each 'hot' lead, to the remaining motor leg) to 'simulate' the presence of a 3rd phase. In this situation, the run capacitors need to be selected to match the motor HP rating, and capacitance on one leg needs to be higher than the other by about a factor of 2. Also, to get the motor to 'start', either a pony motor needs to be connected (to get it spinning), or a rip-cord wrapped around the motor shaft and pulled (Not reccommended by me), or an additional 'start' capacitance can be temporarily placed across the larger RUN capacitor bank (like... about 7x the larger of the RUN cap banks) to kick the motor in the right direction... once the motor is up to speed, the START caps can be removed, and the motor will continue to run. This is referred to as a 'static converter'.
3) The last method, is to make a 'rotary converter'. The rotary converter is essentially a single-phase to 3-phase transformer... it uses a surplus 3-phase electric motor, rigged up with a 'static converter' (described above) to start and run. Once running, the electric motor's A, B, and C phases will provide 3-phase AC out to operate another tool. To clarify how this works, the 3-phase motor is actually used as a rotating transformer... the motor's windings GENERATE the 3'rd phase. The 180-degree single-phase power is fed across two (120 degrees) of the 3-phase 'idler' motor's windings, and the result is a 3rd phase of power out. In a rotary-converter, the converter's idler-motor must be about 25% larger than the load you plan on running.
