# How To Calculate Transformer and Battery Specsfication On Inverter.

## Calculating Transformer and Battery Specs

While making an inverter, two calculations must be broadly taken into account, viz. the transformer and the battery ratings.

1) The transformer must be approximately rated twice the maximum load that is expected to be used with the inverter. For example if the intended load is 200 watts, then the transformer must be rated at minimum 300 watts. This will ensure a smooth running of the inverter and less heat generating from the transformer.

The voltage rating of the transformer must be slightly lower than the battery voltage for square wave inverters.

However, for concepts involving PWM or SPWM, it should be equal to the average voltage applied at the gates of the MOSFETs. This can be measured by measuring the average DC voltage applied at the gate of the MOSFETs from the oscillator stage. So, suppose your battery voltage is 12 V, but because of PWM your average switching voltage from the oscillator shows 7.5 V DC, that implies your transformer must be a 7.5-0-7.5 V and not 12-0-12 V.

2) And the battery Ah must be rated 10 times more than the maximum current rating of the load. For example if the battery is 12V rated and the load 200 watts, then dividing 200 with 12 gives us 16 amps. Therefore the battery Ah must be 10 times of this amp rating, that is 160 Ah. This will ensure your battery runs with a healthy 0.1C discharge rate and provides a back up of around 8 hours.