(08-07-2017, 11:18 PM)artistwantab Wrote: Some have said that the Phase Convertor will be cheaper then then a motor. I googled and found the opposite to be true. Making not finding the right thing.
Anyone have some brand names of links for the phase convertor and/or motor. I would like start saving my pennies.
In no particular order, there are unbalanced static converters, balanced (somewhat) static converters, rotary converters, solid state phase converters, and VFD's.
Unbalanced converters are just motor starters, which create a third phase using some capacitors and a relay, and only work to start the motor. After that, the capacitors are cut out and the motor runs on single phase power, at much reduced max output power.
Balanced static converters may or may not have a relay for starting capacitors, but they have run capacitors that stay in the circuit and create something of a third phase while the motor is running.
Rotary converters are really balanced static converters with an added 3-phase motor which acts as a rotary transformer. They're better at creating that third phase, and would normally be sized for the FLA of the load motor, if max output power is required for extended duration or continously, as under varying load the current will be unbalanced. But it's at full load where it most matters since current draw and therefore heating is highest.
Solid-state converters convert the single-phase mains AC power to DC current, charge and maintain a bank of capacitors, then create a 3-phase 60Hz AC waveform from that DC by rapidly switching power on and off in narrow slices (many thousands of times per second), with the ratio of 'on' time to 'off' time in each slice varied to make an effective voltage that follows a sine wave (well, three of them, since it's 3-phase output) - the higher the on to off ratio, the higher the effective voltage is at that instant along the wave.
A VFD is the same thing as the solid-state converter, but with the ability to adjust the the output frequency of the waveforms. An AC induction motor runs at a speed proportional to the frequency of the power, so to slow one down, you slow down the power frequency. For a table saw that's not usually an advantage, but it does allow you to start it (or any such machine) slowly, and even stop it slowly. Or quickly (with additional braking resistors). And do some other things that aren't really germain to your application.
Twice before I posted info on static converters, in part because you have a lot more motor than you really need, but then deleted that part because it hurts my sense of propriety to talk about them. But they're cheap, and may be something to consider. [Dr. Smith voice]Oh, the pain, the pain.[/DSv]
A VFD is, IMO at least, probably your best bet for a turnkey fix here. Replacing the motor means you'd have to buy a, or reconfigure your existing 3-phase (if it's even there), motor control. A VFD
is a motor control. Add an external start/stop station, which you may be able to salvage from the existing control (again, if it's even there - haven't seen it in any pics), or buy one with decent buttons, wire it up, and go to work, while keeping the extraordinarily smooth operation of the three-phase motor.*
*3-phase power, and motors, and generators, are constant-power, meaning the total power combined between the three phases is a constant at any point along the wave form. Single-phase power, on the other hand, is a series of pulses, going to zero as the wave form crosses zero, which it does twice per cycle, so you get 120Hz pulsing which you can feel in a large single-phase motor. A large three-phase motor has very little ripple in its output, vanishingly small compared to single-phase equivalent. Which is why folks like them on machines that need to run smoothly, like wood machines. Not so important in a fan, for instance. Most of the vibration in my 3 hp single-phase Unisaw is from the motor, in fact, and only when it's under power (with the belts off). Shut it off and that vibration instantly goes away.
