Variable Frequency Inverters
Three-phase induction motors have several advantages but energy conversion efficiency isn't one of them. The biggest advantage is starting torque and lack of extra required start components. They also tend to be smaller for a given horsepower as compared to single phase motors and have smoother torque curves over a wider frequency range.
The big game changer is that of variable frequency inverters. One of these coupled to a 3 phase motor allows for amazing control of speed, torque and direction. The use of a VFI can in many cases replace change gears and transmissions. We recently bought a new mid size CNC lathe at work, there is no variable gearing in the spindle drive at all. Just a 25 HP 3-phase motor and a variable frequency inverter drive. The lathe can run in either direction from 300-4000 RPM with almost no change in torque. It even ramps speed dynamically with changes in diameter and can reverse almost instantly for cutting with left-hand tooling!
One added advantage of the variable frequency inverter is that they can supply 3 phases from a single phase power. This can make for a economical way to run 3 phase motors in a home shop environment and additionally you can get some degree of speed control to boot!
Three-phase induction motors have several advantages but energy conversion efficiency isn't one of them. The biggest advantage is starting torque and lack of extra required start components. They also tend to be smaller for a given horsepower as compared to single phase motors and have smoother torque curves over a wider frequency range.
The big game changer is that of variable frequency inverters. One of these coupled to a 3 phase motor allows for amazing control of speed, torque and direction. The use of a VFI can in many cases replace change gears and transmissions. We recently bought a new mid size CNC lathe at work, there is no variable gearing in the spindle drive at all. Just a 25 HP 3-phase motor and a variable frequency inverter drive. The lathe can run in either direction from 300-4000 RPM with almost no change in torque. It even ramps speed dynamically with changes in diameter and can reverse almost instantly for cutting with left-hand tooling!
One added advantage of the variable frequency inverter is that they can supply 3 phases from a single phase power. This can make for a economical way to run 3 phase motors in a home shop environment and additionally you can get some degree of speed control to boot!