UPS Supply and Raw Power

1) use static switch. google it.

2) use a contactor with input from an undervoltage relay, so that when ups power goes down, raw power comes in line.

It can be done with two power contactors and two control transformers , wired in proper combination . Care is to be taken so that when the contactor for UPS power is energised , its auxilary contact ( NC ) should prevent the RAW power contactor from energising . When the UPS power fails the auxiliary contact of UPS power contactor would make the RAW power contactor to pick up. Here the hitch is a bumpless change -over is very difficult to achieve .

Sounds good to me. Consider a mg-set to smooth out the bump. The various supplies spin the mg-set's motor, and its gen side drives the final output.

1) A UPS Supply can be given as a redundancy for a raw supply .

2) Since you are not going to syncornise both source frequency is not a issue .

3) use a NC interlock between two source .

This depends on the nature of loads you are using from the UPS power. Is the momentary loss of power allowed for the load? If the answer is 'No', use Static Transfer Switch (STS) which works like make-before-break or close transition, otherwise use a regular transfer mechanism, break-before-make or open transition.

Static Transfer Switch (STS) transfers power from a failure (or faulty) source to another standby source (from UPS to Bypass for Online UPS and Bypass to UPS for Offline UPS system). STS constantly monitors the condition of both sources and it transfers the load from failure (or faulty) source to the healthy source within few milliseconds (almost zero-break time) and thus the load doesn't experience the power loss during the transfer.

- MS