Hello,

In my mind, there are two ways to do this. However, I don't know pros, cons, and cost-effectiveness of each.

http://lh6.ggpht.com/_X6JnoL0U4BY/S26tzJ3HCtI/AAAAAAAASCI/p_k2WzgjVb4/tmp166_thumb.jpg?imgmax=800
The link above presents driving one from SCRs. The 4 SCRs can't reverse the motor's direction, thereby requiring another four to do so. However, as shown, the topology is work best with 3 phase.

The other way is using a bridge rectifier and a dc-dc converter to convert 220V to 48Vdc. Subsequently, a h-bridge mosfet driver is conneted to 48Vdc to drive my motor. This allow me to control both speed and direction. However, the converter requires a transformer for safety. I'm afraid that the transformer will dump the overall efficiency down.

Which way should I take? Is this a trading off between smoothness of dc voltage across the motor and the overall efficiency?

Thanks
BlackMelon

 

A 400Va transformer is not that large and will allow PWM H bridge which is more efficient than SCR control on 1ph.
A 48vac secondary will give you ~60vDC after smoothing.
This is no problem with PWM as the recommended DCV is +10% of motor rating, minimum.
The rpm can be controlled by the drive.
http://tahmidmc.blogspot.ca/2013/01/using-high-low-side-driver-ir2110-with.html
Max.