The US National Electrical Code specifies requirements for Class 3 energy
limited circuits. The theory is that the risk of fire is minimal since the
energy is limited to a maximum of 150VA for inherently limited sources. The
voltage is limited to 100 Vrms. The Code makes no mention of a maximum peak
voltage as it does for Class 2; therefore, non-sinusoidal signals are
allowed as long as the rms limits are observed. UL 1012 contains the
requirements for testing a power supply to Class 3 limits, but they have
added a limiting peak voltage of 142 V.
A NRTL is reviewing one of our products and we have a disagreement for the
need for this peak voltage rating. Our argument is that the rms limits are
sufficient since the Code makes no mention of a peak voltage limit. Having
peak voltages greater than 142 V while maintaining the rms VA rating does
not compromise the energy limitation.
Are we missing any critical information that would support the need for a
peak voltage limit in order to limit a fire hazard?
Richard Woods
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
To cancel your subscription, send mail to:
[email protected]
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Jim Bacher: [email protected]
Michael Garretson: [email protected]
For policy questions, send mail to:
Richard Nute: [email protected]
