The air-core auto-transformer in a 66 kV fault ride through test setup for wind turbines is prone to discharges. Their root-cause is identified as switching overvoltages (OV) due to current chopping (CC). The coil is modelled as an equivalent circuit using analytically calculated parameters. A simulation in the time domain shows significant OV with a magnitude of up to 11 p.u.. A comprehensive discussion on potential counter-measures proposes a snubber circuit as a feasible solution to mitigate the discharges. The OV is defined by the snubber's RC component and the magnitude of CC. The simulation results show that the OV is reduced to less than 2 p.u. by including the snubber circuit. As future work, a measurement campaign to determine the value of the chopping current is suggested.