The V-Lock Cord Retaining System prevents accidental power interruptions.
Electrical equipment in the medical field must not place patients or medical staff in harm’s way. Designing safe equipment starts where power is supplied. New medical devices require that power connectors and power entry modules fulfill the base standard for medical electrical equipment, IEC/UL 60601-1. A short circuit or residual current can trigger a protective system upstream and in doing so possibly shut down other life-sustaining equipment. Thus, it is necessary to pay special attention to how each unit is supplied with power. Recent ideas from our company for connectors and power entry modules comply with these standards and generally can be used in most equipment without additional testing.
Medical equipment is governed by IEC/UL 60601-1 and harmonizes with both North America and Europe safety requirements. An important recent addition to this basic standard for medical devices is IEC/UL 60601-1-11 for protection in a Class II environment.
Shorter hospital stays mean manufacturers of medical devices are being presented with new challenges to minimize the safety risks associated with the use of in-home medical equipment. Because these medical products are operated by laypersons with little medical training, regulatory requirements have been established to provide safety measures specifically for the patients and operators.
SCHURTER’s DC12, Power Entry Module with Filter is approved for Protection Class II.
For instance, the IEC 60601-1-11 safety requirement places several restrictions on in home medical equipment, such as:
♦ Altered ambient conditions (storable at -25 to 70º C and operation at 5 to 40º C with RH at 93%)
♦ Protection Class II (no protective earth connection is permitted)
♦ Enclosure protection from water and dust must be at least IP 21 (light rain)
♦ Stricter shock and vibration tests (30 min random vibration test per axis)
Devices certified to Protection Class II have double insulation between the main circuit and the output voltage or metal enclosure. Even when they have electrically conductive surfaces, they are protected against any contact with other live parts through the double insulation.
Our company offers various combination connectors that satisfy the IEC/UL 60601-1 requirements, as well as connectors that meet the stricter requirements from IEC/UL 60601-1-11 for Protection Class II. One such module, the DC12 power entry module with EMC filter and line switch, provides double insulation between energized components and exposed parts, and complies with equipment level standard 60601-1-11. All company filtered connectors for Protection Class II design have been high-voltage tested to 4,000V. Every one of these manufactured components is tested before leaving the factory.
A must for medical equipment
Protecting equipment operators and patients is paramount, so special attention must be paid to effectively suppress transients on the conductive lines. Most standard devices today are supplied with power by switch-mode power supplies. These are suitable for the various main voltages around the world. Due to the fast-switching capability by ICs, they have a high efficiency.
These switching ICs, however, cause great interferences that can be measured on the power mains. EMC standards specify limits for conducted and radiated interfering voltages for medical equipment. This is a precondition for compliance with the EMC standards, which in turn is necessary for CE conformity marking. The use of a line filter is recommended.
This can be a standalone block filter or a line filter in combination with the connector. Because the ground connection is missing in IEC appliance inlets with Class I, medical M5 filters, and Class II configurations, the filter has to make do without ground capacitors. These so-called Y-capacitors are widely used in most filter circuits because they offer good attenuation in higher frequency ranges (>1 MHz). The attenuation loss can be compensated by more inductivity or by attaching ferrites to the power cable. However, as this is not always practical or even possible it’s recommended to deal with interferences in this frequency range as close as possible to the source of the interference. A power entry module with filter meets this recommendation by providing a line filter directly on the mains.
Asymmetric attenuation curves come from a 1 A filter with Y-capacitors (top line) and without Y-capacitors (bottom line).
Power cord retention for additional safety
Medical devices can be connected directly to the mains or with a detachable power cord. However, mobile devices, such as analytical apparatuses, diagnostic devices, endoscopy equipment, or laboratory equipment work in environs with greater danger of an accidental power-cable disconnect. Detachable plug connections must meet the requirements of IEC standard 60320. Depending on the application, it is recommended to include a mechanism to protect against any unintentional plug removal from the equipment’s power socket.
The most common type of protection against inadvertent disconnection is a cord-retaining bracket. However, it is critical to select the correct bracket shape because there are many variations depending on plug type and size as well as the equipment use.
The application examples are for various mating connectors.
The V-Lock cord retaining solution, a simple attractive and alternative system to brackets, provides a better solution. With the V-Lock solution, the power socket is equipped with a notch that interlocks with a special latch on the power cord connector. Unlike brackets, the system forces the user to lock the cordset to the connector for operation which ensures the cord from being unintentionally removed from the socket. The V-lock solution makes unnecessary an additional cord-retaining system specific to a unit’s power socket or retaining bracket.
