The Off-Line Tesla Coil

Tesla Coil Number 2...still a work in progress

An off-line Tesla coil is a coil that is powered directly off the AC mains voltage (no need for the 15kV neon sign transformer). The lossy and inefficient spark gap is replaced by a solid state switch. I will be using an IGBT that I had acquired from salvage at work.

The IGBT I will be using is a 2500V 1200A (2400A peak!) monster. I have it attached to a test capacitor bank in the picture on the left. The white boxes are snubber capacitors, (also compliments of GE salvage). I'm using double sided copper clad circuit boards as a makeshift bus-bar to minimize the stray inductance.

  This is the basic schematic of an OLTC. When the IGBT is off, the Cap bank is charged up to 1000VDC. Once the IGBT is turned on, it shorts the capactors causing a large current through the Primary coil. This creates a large voltage in the secondary.

  Here's a video of it in action. (or here if the embedded video doesnt work tc_1_10_07019.mpg)