Canadian Standards Association Certification Requirements for Telephone Equipment Power Supplies

The Canadian Standards Association is a non-profit organization dedicated to the writing of Standards, and Certification of products to these Standards. Although CSA Standards are voluntary, with reference to telephone equipment power supplies compliance to the applicable Standards is made mandatory by the Canadian Federal and Provincial Governments. These are electrical safety Standards addressing fire and shock hazards. The Canadian Electrical Code Part I contains requirements for the installation of electrical equipment, and in U.S.A. this corresponds to the National Electrical Code. There are CSA Standards which contain construction and test requirements for the telephone power supplies. Some of the items that are covered by the Standard are: - Enclosure: Openings permitting access to live electrical parts, openings permitting material to fall out of the enclosure, material flammability, mechanical strength. - Mounting method. - Wiring methods. - Creepage and clearance distances between live parts of opposite polarity. There are additional requirements of uninterruptible power supplies that incorporate a static transfer switch. Since these devices contain two ac power sources (i.e. ac line and an inverter) there is a danger that the two sources may inadvertently be interconnected due to a component failure. Tests are performed to verify that should a static switch leg fail "ON" power cannot backfeed and energize circuits which are not supposed to be live. There are also requirements unique to inverters specifying the waveshape and output voltage.