Oil boiler igntion transformer.

[Murphyv310]

Nasty belt off them. Had one on a diesel hot water pressure washer a few years back. There are different types, mains transformer and inverter. Some for single and others for two electrode spark electrodes. Volts between 6 to 12kv

Here's one. http://www.abb-furnace.com/furnace-acces...t11-m.html

https://www.anglonordic.co.uk/burner-spa...rahma.html