Why is UL changing its motor standards? This is generally the first reaction when people hear that UL is changing its venerable UL 1004 and UL 2111 standards for electric motors. Part of this reaction is due to the perception in some quarters that UL serves as the “Safety Police.” Another part of the reaction may be due to the comfort level that engineers have with the previous set of requirements that were first printed in 1972 and are well recognized by manufacturers.

The answer begins with the fact that UL envisions its role as symbiotic with the motor and appliance industries. UL serves as a catalyst for bringing safer products to market by keeping our nationally accredited requirements current and responsive to emerging technology. The standards represent one of our tools in being able to do that. Like any tool, to be most effective, it needs to be maintained and kept current with prevailing and emerging technology.

So, the new standards weren’t written with the intent of making requirements restrictive. UL’s ANSI-accredited role requires UL to be responsible for coordinating and assuring consensus in product safety concerns. As part of the standards development process, UL has the ability to propose new requirements, but if the other 38 members don’t agree with the recommendation, the proposal would be voted down.

In addition, everyone recognizes that safety in any product is not an absolute. It often involves trade-offs in order to bring the safer products to market and still best address the end-user’s practical needs.  Unfortunately, certain products involve an inherent level of risk if they are to be functional – such as autos, for example. 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:

• UL 1004-1 – Rotating Machinery: This contains requirements common to all rotating machines.
• UL 1004-2 – Impedance Protected Motors: This contains requirements specific to this design.
• UL 1004-3 – Thermally Protected Motors: This contains requirements specific to motors protected by any one of five different technologies of thermal motor protector devices.
• UL 1004-4 – Electric Generators: This contains requirements for component electric generators, sometimes called generator heads.
• UL 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:
• Electronically Protected Motors: This will address both BLDC (electronically commutated) motors as well as conventional motors protected by electronic circuitry.
• Servo and Stepper Motors: This contains requirements specific to these very specialized motors.
• Inverter 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 over-surface 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.