Features

Electrical equipment used in medical technology must not place patients or medical staff in danger. This, in turn, requires that designing safe equipment starts at the point where the power is supplied. Power connectors and power entry modules with or without a powerline filter must fulfill the requirements of the base standard for medical electrical equipment, IEC/UL 60601-1.

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Fig. 1 – V-Lock Locking System with hospital grade plug.
Medical technology uses a wide range of electrical equipment. During normal operation and in the event of a malfunction, it is imperative that the equipment does not pose any danger to patients or medical staff. A piece of equipment that causes a short circuit or residual current can trigger a protective system upstream and, in doing so, shut down other, possibly life sustaining equipment. Thus, it is necessary to pay special attention to how each unit is supplied with power.

Connectors and power entry modules used in the equipment are tested to component standards and, if in compliance with these standards, can generally be used in most equipment without additional testing. This is especially true for medical equipment, where extensive requirements regarding safety are in effect, as defined in the base standard for medical electrical equipment, IEC/UL 60601-1. In addition, there are a wide range of specific requirements for each category of equipment according to IEC 60601-x-xx. The IEC standards for medical electrical equipment are harmonized with UL so that the same requirements are also in effect for equipment in North America.

Power Feed

Medical devices can be connected directly to the mains or with a detachable power cord. Such plug connections must meet the requirements of Standard IEC 60320. Depending on the application, it is recommended to include a mechanism to protect against any unintentional removal of the plug from the equipment’s power socket. The most common type of protection against inadvertent disconnection is a cord-retaining bracket. Depending on the type of equipment and because of the many types and shapes of power sockets, it is important to select the correct bracket shape. There are cord-retaining brackets for most power sockets.

In addition, SCHURTER offers a VLock cord retaining solution, a simple alternative system to using brackets. In the V-Lock, the power socket is equipped with a notch that interlocks with a special latch on the connector on the power cord. The system prevents the cord from being pulled out of the socket unintentionally. The advantage of this is that no cord-retaining system specific to a unit’s power socket or retaining bracket must be adapted and attached. A “hospital grade” cord set is available for medical applications in North America. (See Figure 1)

Fuseholders

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Fig. 2 – Power entry module for safepower feeds.
Permanently installed medical electrical equipment comes with its own fuses. If there is a failure in a piece of equipment, a fuse prevents that unit from tripping the circuit breaker and disconnecting other, sometimes life-critical devices, from the mains. Equipment manufacturers must ensure that energized supply leads are protected by a fuse. A few power distribution networks, however, are not polarized. That means that the power plug can be inserted in such a way that the energized conductor can be on either the plug’s left or right pole (e.g., Schuko plugs in Germany). As a result, the equipment fuse could be protecting the neutral conductor, which results in no protection against a short circuit to earth. (See Figure 2)

Therefore, it is recommended that all medical electrical equipment be equipped with a double pole fuse holder. It must further be ensured that only authorized personnel can remove or replace fuses. The basic standard for medical electrical equipment, IEC/UL 60601-1, specifies fuse holders that can only be opened up with the help of a tool.

Switches

The line switch at the power feed has an important function. Just as with fuse holders, it must be ensured that the equipment is completely disconnected from the power network after being turned off. If only one pole in a nonpolarized power distribution network is interrupted, the equipment could still be live. Thus, it is preferable to use a switch that disconnects the power feed on two poles. (IEC 60601-1: 8.11.1)

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