Power supplies and cords for medical equipment
Helpful steps on meeting IEC Standards
Whether you’re traveling for business or pleasure, it’s important to know the rules and customs of the places you’re visiting. The same holds true when it comes to power cords and power supplies: Many countries have hospital-grade or medical applications standards for these supplies, and the safety of patients and equipment is at risk when these standards are not met.
This includes meeting IEC medical equipment standards, including IEC 60601-1 approval. In this article, we’ll look at some of the criteria for selecting power cord supplies to adhere to these standards.
Medical-grade power supplies are required to meet IEC 60601-1 safety standards as set forth in regional versions such as EN60601-1 and UL60601-1. These standards levy additional safety regulations on issues such as creepage and clearing space, leakage current and isolation voltage. UL60601-1 limits leakage to 0.3 mA of leakage current from input to output on Class 1 equipment.
Patient vicinity and patient connect
Patient vicinity – as defined by UL60601-1 standards – refers to electrical equipment based within six feet of a patient. When equipment comes in direct contact with a patient, this is what is known as patient connect, requiring another level of isolation. Medical grade power supplies typically carry patient vicinity certification as they do not come in direct contact with patients.
Also known as touch current, these are the leakage paths from an enclosure that may come in contact with a patient or operator. As patients under medical care are often in a weakened state, a tiny amount of leakage current can be harmful to their health. The standard mandates a maximum level of 100µA for normal operation and 500µA for a single fault condition.
Output voltage, current and power rating
To meet the application requirement for supply voltage, medical power supplies offer single or multiple output voltage, ranging from 3.3 to 48Vdc. When establishing the supply-voltage level your application needs, look to the current levels required at each voltage. When only one supply voltage is needed, the power rating is the supply voltage multiplied by the maximum current required. When multiple outputs are required, add the voltage-times-current products for all supply voltages to find the power rating.
This refers to the type of cooling required, and is determined by looking at the ambient temperature range expected from the application, along with the thermal specifications of the power supply. Convection cooling may be satisfactory, but forced air cooling may be required.
In addition to the IEC medical equipment standards we’ve already mentioned, equipment may also need to comply with related medical equipment regulations such as IEC 60601-1-2, which deals with electromagnetic compatibility. Aside from these international regulations, it’s important to remember that many countries – including Japan, Australia and Denmark – have specific component requirements for power cords.