Medical safety starts with power input

Medical electrical equipment must not place patients or staff in danger. Schurter steps buyers through some of the safety related considerations. 

Medical devices connected by a detachable power cord must meet the requirements of IEC60320. It is also recommended to protect against unintentionally removing the plug from the socket. For example, with Schurter’s V-Lock cord retaining solution the power socket has a notch that interlocks with a cord connector latch and prevents unintentional removal.

Permanently installed medical electrical equipment comes with its own fuses. It is recommended that all such equipment be equipped with a double-pole fuse holder and that only authorised personnel can remove or replace fuses. The basic standard for medical electrical equipment, IEC/UL 60601-1, specifies fuse holders that can only be accessed with help of a tool. For this, Schurter offers Extra-Safe fuse drawers.

The power feed line switch ensures equipment is completely disconnected from power after being turned off. If only one pole in a non-polarized power distribution network is interrupted, equipment could still be live. It is preferable to use a switch that disconnects power feed on two poles.

The power line filter protects equipment from external HF interference and reduces the HF interference radiated by equipment. They are often necessary to fulfil EMC standards for CE declaration of conformity.

Filter capacitors cause leakage currents which, in medical electrical equipment, may not exceed 100µA under normal conditions (10µA for direct patient contact). Thus, power line filters for medical equipment do not have Y capacitors or only very small ones, resulting in a maximum leakage current of 5µA or 80µA.
Capacitors used are wired directly between the energised conductors (X capacitors) or between the energised conductors and earth (Y capacitors).

If the power cable is removed from the socket, the stored voltage from X capacitors is still present on the power pins and if touched can result in an electrical shock. A bleed resistor is placed inbetween the phase and neutral conductors to discharge the capacitor.