Protecting a power supply from inductive load
A simple series diode would provide considerable protection from an inductive load.  A flyback diode would provide additional protection.







simulate this circuit &ndash; Schematic created using CircuitLab

Edit: the diagram just shows generic 1N4001 diodes.  Make sure the ones you use are rated for the current and voltage you require.  The 1N4001 isn't suitable for large currents.