Appliance Design - May 2008 - (Page 31)

QUALITY & STANDARDS No one would ever buy a car that was absolutely safe. It would be so expensive that no one could afford it. It would be so big and heavy that it would no longer serve its functional purpose. And no one would want it because of what it would look like. So when addressing safety, there is a balance that needs to be achieved that addresses functionality and usability. With this in mind, UL did not write the new standards to be more stringent, but instead to accomplish three tasks: 1. To address new and emerging motor and motor-control technologies that were either not addressed or envisioned when the requirements were first written. 2. To clarify and to remove identified ambiguities from the existing standards so that manufacturers more clearly understand all of the requirements and their intent. 3. To provide alternatives. There is not just one way to build a motor, and, similarly, there should not be just a single way to meet the intent of a safety requirement. Where the legacy of standards consisted simply of UL 1004 – Electric Motors and UL 2111 – Overheating Protection for Motors, the new standards are written as a more functional family that better categorize and organize requirements for specific types of rotating machines. This family scheme should be very familiar to those who are accustomed to IEC Standards. The new motor series of standards now has the following: 4UL 1004-1 – Rotating Machinery: This contains requirements common to all rotating machines. 4UL 1004-2 – Impedance Protected Motors: This contains requirements specific to this design. 4UL 1004-3 – Thermally Protected Motors: This contains requirements specific to motors protected by any one of five different technologies of thermal motor protector devices. 4UL 1004-4 – Electric Generators: This contains requirements for component electric generators, sometimes called generator heads. 4UL 1004-5 – Fire Pump Motors: This contains requirements unique to that specific application. In addition, there are three pending standards to further define requirements and further expand the family of motor standards. These include: 4Electronically Protected Motors: This will address both BLDC (electronically commutated) motors as well as conventional motors protected by electronic circuitry. 4Servo and Stepper Motors: This contains requirements specific to these very specialized motors. 4Inverter Duty Motors: This contains requirements specific to the evaluation of motors intended for variable-speed drives or other non-sinusoidal AC supplies. This family of standards architecture enables UL to build on a continuum of more focused requirements for the various types of rotating machinery. The segregation of the various standards also avoids the result of an enormous, unintelligible document. All of that should shed some light on how UL is addressing the first of the three reasons for introducing a family of standards. Regarding the second goal, it is a given that everyone tries to write standards that are crystal clear and intuitive. Unfortunately, as standards age and numerous revisions are appended, rearranged and tacked on, the original intended clarity inevitably suffers. Eventually, a complete rewrite is required to restore the intended precision, transparency, and user friendliness. As for the third goal, it remains important to understand that the intent of any requirement should be to provide more than one solution to a problem. Inflexibility in the consideration of alternatives simply stifles innovation and creativity in both motor design and appliance design. As noted, UL does not envision its role as the “Safety Police” throwing up barriers, but rather as colleagues of manufacturers desiring to bring safer products to market faster. One example of the alternatives provided in the new standards concerns spacing requirements. Minimum spacing requirements are intended to provide adequate isolation between electrically live parts and dead metal or opposite polarity parts and, in doing so, to reduce the potential for electric shock and/or fire hazard. Historically, this was accomplished through a table of hard and fast spacing requirements. With this approach, if a motor was 1/3 HP, 120 V and 7 in. in diameter, it needed to maintain a minimum of 1/16 in. spacing between live parts and dead metal or opposite polarity parts. Under the new requirements, a motor (or generator) may be designed and built with spacings smaller than 1/16 in. if the equivalent safety can be demonstrated through the use of better materials; demonstrated by test – impulse or dielectric withstand; or by some combination of the two. For example, using the newer requirements, a motor requiring 1/16 in. spacing may be able to utilize lower spacings if the construction passed a dielectric/impulse test of up to 3,300 V. Degrees of expected pollution also can impact certain spacings. At 125 V, an oversurface spacing of as little as 0.28 mm could be allowed if the motor would be used in an environment with no pollution. This spacing would jump up to more than 3 mm if the spacing in question were in a high pollution area with conductive precipitate such as residue from normal wear of motor brushes. This not only results in greater design flexibility for manufacturers, but also results in the possibility of designing motors with much greater efficiency without any compromise in safety. The engineering staff at UL is excited about the release of this new family of standards, and the major motor and appliance manufacturers contacted thus far are equally excited about the potential in the new standards. They are excited about the potential for greater freedom and flexibility of design, the potential for greater motor and appliance efficiency, and the potential for an improved certification experience that is responsive to industry’s desire to bring more efficient and innovative products to market. < For more information, enter . . . . . . . . . . . . . . . . . . 309 www.applianceDESIGN.com applianceDESIGN May 2008 31 http://www.appliancedesign.com

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Appliance Design - May 2008 Contents Editorial Shipments/Forecasts News Watch New and Notable Displays & Indicators Elastomers Quality & Standards Indoor Air Quality IHHS Highlights New Products Classifieds Design Marts Advertiser’s Index Association Report: PSMA

Appliance Design - May 2008

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