Safety and Regulatory Standards Safety and Regulatory Standards When creating a particular product or system, the designer must take into account the fact that the final product will most likely be sold and used worldwide, and may need to be compliant to international safety standards. Electrical safety specifications in general, and particularly those related to power conversion devices, are defined at various product application and functional levels. Once consisting of a myriad of country-specific and sometimes conflicting requirements and definitions, there has been a common consolidation or “harmonization” of these specifications in recent years into those of a more standardized and understandable set as defined by IEC internationally-accepted governing bodies. This guide outlines these commonly used specifications to give the designer a reference point for safety compliant design practice. While the individual power conversion device may carry full safety approvals itself, the incorporation of the converter into the final product or system may often require safety approval itself. Astrodyne’s technical support department can provide guidance to the user concerning their power converter product safety approval specifications and best practice design procedures to help the designer meet overall system safety approval. Because of the breadth and depth of safety specification levels and their continual update and revision, it is highly recommended that a recognized safety agency such as UL or TUV be consulted as to the exact implementation and final acceptance testing of any product using power converters. Common Power-Related Safety Specifications USA UL 60950-1: 2001, 1st Edition 2007-10-31 (Information Technology Equipment- Safety-Part 1:General Requirements) UL 60601-1, 1st Edition 2006-04-26 (Medical Electrical Equipment Part 1: General Requirements for Safety) UL 1310 and CSA C22.2 No. 223 (Class 2 Equipment: Power supply with Extra Low Voltage and limited output power, North America only) CANADA CSA C22.2 No. 60950-1-03 1st Edition, 2006-07 (Information Technology Equipment- Safety-Part 1: General Requirements) CSA-C22.2 No.601.1 M90, 2005 (Medical Electrical Equipment- Part 1: General Requirements for Safety) GERMANY IEC 60950-1:2001, First Edition inclusive of CENLEC Common Modifications. IEC 60601-1: 1988, Second Edition TUV: EN 60950-1 & EN 60601 Essential Safety Specification Definitions The above safety specifications define the requirements that must be met for four basic concepts: Isolation, Spacing, Insulation, and Leakage Current. Isolation/Electrical Strength Isolation strength, commonly referred to as High Potential (HiPot) testing is done to verify the insulation materials used will prevent electrical arcing or breakdown within the circuit paths during a 1 minute duration test. Max Input V. EN60950 IT Equip EN60601 Medical UL1310 125V 125V 250V 250V 2000VAC/2828VDC 1000VAC/1414VDC 3000VAC/4242VDC 1500VAC/2121VDC 3000VAC 1000VAC 4000VAC 1500VAC 1500VAC, P-S 1500VAC, P-Encl. P-S P-G P-S P-G P=Primary Side, S=Secondary Side, G=Earth Ground, Encl=Enclosure 26 Safety and Regulatory Standards Creepage and Clearance Spacing Requirements Creepage and clearance distance specifications are physical spacing requirements that isolate the user from harzardous voltage levels within the system. Creepage: Defined as the shortest allowable distance between two conductive elements or a conductive element and the outer boundary (ie: case) of the system, as measured along the surface of the insulation. Clearance: The shortest distance between two conductive elements, or conductive and bounding surfaces, as measured through air. Max Input V. 125V 125V 250V 250V EN60950 IT Equip Basic Reinforce Clearance, Air 1.3mm 2.6mm Creepage, Distance 1.5mm 3.0mm Clearance, Air 2.0mm 4.0mm Creepage, Distance 2.5mm 5.0mm EN60601 Medical Basic Reinforce 1.6mm 3.2mm 3.0mm 6.0mm 2.5mm 5.0mm 4.0mm 8.0mm Insulation Strength Insulation can take several forms: - Solid insulating material with adequate thickness and creepage distance over the surface of the conductor itself, as in wire jacket insulation - Adequate clearance through air spacing - A combination of both methods Insulation levels fall into 5 basic catagories: Operational Insulation: Minimum level of insulation required for equipment operation. Basic Insulation: Provides basic insulation from electrical shock. Supplementary Insulation: Additional insulation applied to increase protection against shock in case of basic insulation failure. Double Insulation: Construction that uses both basic and supplemental insulation. Reinforced Insulation: A single applied insulation system that provides shock protection equivalent to double insulation. Leakage Current Leakage current is defined as the amount of current that flows from the product or system to earth ground. In cases where system grounding is insufficient or the earth ground connection is interrupted, potentially hazardous levels of leakage current may occur. In patient connected medical equipment applications, such leakage current specifications are more stringent, owing to the direct-connect nature of such systems. There are three major classes of considered equipment for leakage specifications: Class I: Protection of electrical shock is provided through the use of basic insulation and protective earth ground connection to the case of the product or system. Class II: Assumes there is no protective earth ground connection, and relies upon double or reinforced insulation for shock protection. Class III: Relies upon a power source supply from an SELV (Safety Extra Low Voltage) source where hazardous voltages are not presented. Maximum Leakage Current Specifications EN60950 IT Equipment Class I 0.75mA (hand held equipment) 3.5mA (all other types) Class II 0.25mA (all) EN60601-1 Medical Equipment Condition Non-patient contact Direct patient contact (isolated) Non-direct patient contact (isolated) Grounded enclosure Spec. 500A 10A 50A 100A As used with: Printer, peripherals Direct electrode or pads Blood pressure cuff Bedframe, dental chair 27