high voltage driver

 |                                           >             
gnd                                          >R1        
                                             >              
                                             |   
                                             |B        
                                            ---      GND 
           T1:NPN Power Transistor:2N3055  C/ \E     | 
                                           /   \     |
                                          | TVS |    |
                                      ----+->|<--+----+

TVS: This is a back EMF snubber. It may composed of a variety of components to suit. Sometimes you see zeners, or RC circuits, or transorbs (transient voltage suppression diode). Transil diodes provide high overvoltage protection by clamping action -- Part number 1.5KE15CA

A neon indicator bulb with a resistor in place of the TVS can be used to indicate when EMF is over 100 V.

Designing RC Snubber Networks

media:igbtAPPguide.pdf

Misc notes

L = N² * p * A / l

• L = inductance in Henrys
• N = number of turns of wire (straight wire = 1)
• p = permeability of the core material
• A = are of the coil in square meters
• l = average length of coil in meters.

Determine saturation by noting curve of values at different power levels. For example, determine when temperature sharply swings up as voltage or load increases.

More information

Samuel M. Goldwasser's Gadget FAQ with info on High Voltage