Mains transformers that are used in medical applications require a protective device to ensure the insulation does not overheat in the event of an overload or short circuit condition. All VPM series transformers have an integrated thermal switch within the windings. Depending on the voltage range, there are some important differences between the 25VA and 1kVA range and the 1kVA and higher range. This slide details the differences here to show the user how these protective devices are applied depending on the voltage range.