Need for multiple transfer switches for emergency and standby power generation systems

Automatic multiple transfer switches are widely used in most emergency and standby power generating systems, because of their reliability.
Some of these automatic multiple transfer switches also support over current protection and are designed as per the guidelines stated in NEC, which are deemed as yardsticks, as far as measuring the standards within the electrical industry is concerned.
These transfer switches are held mechanically, and are operated electrically, directly from the power source. They are known to transfer the load to the electrical equipment with greater reliability and accuracy when compared to the conventional switches. These switches are normally placed at the mains or at the secondary bus distribution terminal, and are responsible to feed the load to various branch circuits.

Depending on their placement, automatic multiple transfer switches are designed as per the individual requirements of the circuit and the equipment being served. There are a wide variety of automatic multiple transfer switches available in the market to choose from. Depending on their functionality, one can choose the right switch depending on its ability to perform a particular duty.


Following are some of the parameters you might want to look at, before zeroing on a particular automatic multiple transfer switch:

• Its capability to lock strong inrush currents


• Its capability to continuously carry full-rated current from normal as well as emergency power sources


• Its capability to rebound fault currents


• Its capability to close on currents carrying full load, for a given number of times, as per NEC and other international standards


• Its capability to accommodate electrical spacing, as well as insulation, for two power sources that run unsynchronized

The photograph above depicts an automatic multiple transfer switch being used for a double-throw circuit, in order to minimize losses in one of the power sources, by providing ‘locking’ protection.


Apart from power outage, power supply to the most critical equipment in an emergency locality, such as a medical facility, can be interrupted by:

• Any open circuit on the load side in the premises of a medical facility or a building that can interrupt the incoming power supply. (This kind of power interruption generally happens in cases where single switch transfer system is deployed even in emergency areas. Using single switch operating systems in emergency areas may lead to valuable data loss, irreversible property damage and sometimes, may even cost lives).


• High inrush or fault currents


• Overloaded circuits


• Failure of the power generating system within the premises of the building due to mechanical and/or electrical malfunctions

Therefore, in places where continuous power supply is deemed necessary, it is inevitable that you use automatic multiple transfer switches, which are capable of supplying power continuously with the help of alternate switches (even when the switch connected to the actual supply fails, or the circuit is open), without causing any potential damage.

Conclusion

In conclusion, I would like to say that this is the most important reason why electrical engineers demand using automatic multiple transfer switches at places that require uninterrupted power supply.
If you are low on budget, but want optimum safety in your premises, then it is recommended that you use lower current rated switches at the load ends, and use one higher rated automatic multiple transfer switch at the mains (incoming end).

This combination can be very economical and safe at the same time, without being heavy on the pocket.