What role do transformers play in ignition circuits for oil furnaces?

In oil furnace ignition circuits, transformers are used to step up standard line voltage to a high voltage level required to create a spark at the burner electrodes. This spark ignites the oil-air mixture during startup. The ignition transformer ensures reliable, repeatable ignition by delivering stable high-voltage output under varying load and temperature conditions. Without the transformer, sufficient voltage could not be generated safely or consistently, making combustion unreliable and increasing the risk of failed starts.