if its a bench top demo you wont be loading it hard, it'll be fine - if it was 1 HP or so, get 3 or 4  22uF caps
for example some light switches  will allow you to vary the C value and bolt it all securely to a block of  wood- actually for any  motor demo clamping it down  is by far the most important part - avoids it  rolling off, taking the mains leads with it and hurting someone. Its also a good idea not to use anything too  big on a bench any way - imagine it going for a spin at near synchronous speed if the supply is accidentally shorted so the rotor locks up.  ?


If you can muster an oscilloscope and some mains rated probes you can also look at the phase voltage varying as it spins up. An isolation transformer may be a good idea, as well as a supply side RCD.



totally unloaded, you may be able to run it single phase and decide it which way to start by pulling on the belt  to give it some pre-spin one way or the other before energising.


Don't do so many starts and stops in a short time that it smells of burning though.



You don't mention the motor rating, but again I caution demos of anything too big unmounted.

if its a bench top demo you wont be loading it hard, it'll be fine - if it was 1 HP or so, get 3 or 4  22uF caps
for example some light switches  will allow you to vary the C value and bolt it all securely to a block of  wood- actually for any  motor demo clamping it down  is by far the most important part - avoids it  rolling off, taking the mains leads with it and hurting someone. Its also a good idea not to use anything too  big on a bench any way - imagine it going for a spin at near synchronous speed if the supply is accidentally shorted so the rotor locks up.  ?


If you can muster an oscilloscope and some mains rated probes you can also look at the phase voltage varying as it spins up. An isolation transformer may be a good idea, as well as a supply side RCD.



totally unloaded, you may be able to run it single phase and decide it which way to start by pulling on the belt  to give it some pre-spin one way or the other before energising.


Don't do so many starts and stops in a short time that it smells of burning though.



You don't mention the motor rating, but again I caution demos of anything too big unmounted.