10.5 Inverter

In general inverter system shall be provided for house lighting, shop lighting, etc, with the following provisions:

a) Adequate rating of protective devices such as MCB, MCCB, fuses, ELCB, etc, shall be provided at both incoming and outgoing sides.

b) Earthing shall be done properly.

c) Adequate ventilation space shall be provided around the battery section of the inverter.

d) Care in circuit design to keep the connected load in such a manner that the demand at the time of mains failure is within the capability of the inverter. (If the inverter fails to take over the load at the time of the mains failure, the purpose of providing the inverter and battery back up is defeated.)

e) Circuits which are fed by the UPS or Inverter systems should have suitable marking to ensure that a workman does not assume that the power is off, once he has switched off the mains from the DB for maintenance.

f) UPS systems and Inverter systems have a very limited fault feeding capacity in comparison to the mains supply from the licensee’s network. The low fault current feed may cause loss of discrimination in the operation of MCB’s, if the Inverter or UPS system feeds a number of circuits with more than one over current protective device in series (such as incoming MCB at the DB and a few outgoing MCB’s). The choice of MCB’s in such cases has to be done keeping the circuit operating and fault condition parameters under both (mains operation and UPS operation) conditions.