Longer electrical cords tend to have antennalike qualities by attracting the wavelengths of certain signals. This Electromagnetic or Radio Frequency Interference (EMI/RFI) can be troublesome in applications where EMI must be measured in microamps vs. milliamps for safety purposes, which is often the case in sensitive medical applications use.
“In regard to medical equipment,” said Dan Ford, Interpower® Technical Support Specialist, “if you go beyond the 12–15 feet length for medical cords, it becomes much more difficult to meet the equipment standard requirements for resistance and leakage current for the entire system. You don’t want high levels of EMI/RFI in equipment attached to the patient.”
While medical applications standards allow minute leakage current in proximity of the patient, many cords in hospital applications are not “patient connected,” and can therefore be measured in milliamps if the medical equipment is a safe distance from the patient. They can also be used safely in medical office applications.
“Currently there is no UL standard for Hospital Grade cord length,” Ford said, “which is likely due to there being hundreds of standards covering a host of medical equipment with differing requirements.”
Still, cutting back on the length of the cord connected to the power main may not solve your EMI issues. Let’s say you even add an EMI/RFI filter. Now you’ve added a layer of redundancy to lower your interference. You should be good to go, right? Maybe. Ford presses home the point of “cord calculation” for every electrical design.
“If you plug your main power cord into an Accessory Power System (APS), then plug additional accessory cords into peripheral equipment, you must calculate total cord length (not just the main power cord) to get total resistance and leakage current,” Ford said. That is, a 50-foot cord, plus four 10-foot cords into the same system would calculate to 90 feet of resistance and current leakage. This may affect equipment performance, or take you beyond the limits of the specific standards you are complying with.
Interpower manufactures electrical cords, cord sets, and cable with its industry-unique 1-week lead-times! Since 2008, Interpower has maintained its 1-week lead-times until briefly interrupted by material shortages and port lockdowns affecting the supply chain—1-week lead-times are back! Order 1 cord or 5,000 cords. Customized lengths, colors, packaging, and scheduled and blanket orders are available.
