single and 3 phase motor sizing and mounting ?

[m_c]

I'm going to guess it was one of the standard/non-rotary phase converters he used, and the motor has burnt out because you have to derate them when running on a static converter.

What you can replace it with depends on how much starting torque is needed. You can get high starting torque single phase motors, but they are quite a bit more expensive (search for capacitor start motors).

[birchy]

If it's 1400RPM, then it's most likely a 4-pole motor - the question is: have the manufacturers used a 4-pole for the extra torque or was it purely a speed related thing? Most single phase motors will have a capacitor start. Basically, the bigger the capacitor, the greater the starting torque.

You'll probably need to match the motor frame size and mounting type, but I see no reason why a single phase motor can't be used. The other option is to go for a 3-phase motor but use a VFD (Variable Frequency Drive) inverter to drive it. You can get some decent single phase in/ three phase out drives nowadays for around £100. TEC motors are decent and usually a bit cheaper than the Italian ones. Another option is to get a used 3-phase motor from a scrapyard. They're usually good motors which have been removed from industrial machinery. More importantly, they're about £5 each and can be driven by a VFD...

[m_c]

Capacitor start motors (I think officialy they should be called capacitor start/capacitor run) use a centrifugal switch to disconnect the start capacitor once upto speed, otherwise the motor will cook itself pretty quickly.

Having said that, a 3phase and VFD is probably a more practical option. If a high startup load is involved, you might need to oversize the VFD a bit to give a bit more current for startup purposes.

[EddyCurrent]

According to the data sheets the 0.75kw 3 phase 4 pole motor produces about 5.1Nm torque but you have to go to a 1.5kw single phase 4 pole motor for that same torque.