What is the name for unidirectional arches coming out from a bridge rectifier?

If you're filtering an unregulated power supply, huge capacitors won't hurt. But large capacitance on the output of an active supply will slow the response time. There is a trade off with regulation response time and how much ripple you get.
 
90 or 180v dc motors used in equipment like treadmill relies in the zero crossing to be able to control speed.
https://www.grainger.com/product/5X412 devices like this essentially work like a wall light dimmer.

Also, switch and fuse rating for unidirectional arches are comparable to AC rating.

A steady 90v DC can't be controlled with a simple SCR and switches and fuses are completely different as well.
 
Top