can DG's be used as a backup for single phase and three phase ac?
Of course diesel-fueled engine generators can be used a backup, i.e. standby or emergency power. They can also be used as prime power (on all the time). If you need to supply a single phase load, either use a single phase generator (only available for small loads), or use a larger three-phase generator and make sure it has a Y-grounded connection. Even better, get an electrician or electrical engineer to choose the right device for your system.
Yes but they need to match the power source they are replacing.
