E = -L(dI/dt)
Both posts make good points, but lavenatti's right, it's the lack of a protection diode that's blowing your parts. It's a common mistake. Are you finding that your 2N3055s are blowing up as well?
When the current through a coil changes with time, an electromotive force is induced in the coil. Faraday's law says that an instantaneous change in current will produce an infinite voltage. Instead of that happening, the silicon junctions in the coils' path break down and provide a path to ground. You can bypass the coil with a diode, zener, or a snubber (RC); power supply rectifiers like the 1N400x are often used. You'll often see the diode wired across the coil in a reverse-biased manner, this basically provides a short circuit for the transient (notice the minus sign in the equation...).