If a UPS is being approved to UL1778, the backfeed test can be conducted with a linear load if the UPS is specified for use with linear loads. With a linear load the UPS will not have any voltage on the plug pins when running off batteries, but if a non-linear load (such as a computer)is used, there is a voltage on the plug pins (around 60 volts peak).
This creates a problem if your product is being approved to UL1950 and incorporates a UPS. It will not pass the capacitor discharge test and you are responsible for fixing the problem in your unit in order to obtain approval. Berri Remenick Safety Compliance Engineer Washington Laboratories, Ltd. -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of [email protected] Sent: Tuesday, August 17, 1999 1:43 PM To: [email protected] Subject: UPS Hello all, I was wondering if anyone had a comment on the following: Most uninterruptible power sources (UPS) have a unique characteristic. There exists an "energy" (albeit small) on the outlet plug prongs even when the unit is not connected to the mains supply. I have been told that it won't "Bite" you (~3ma @ 30-60vac) and that this is "caused by the continuous neutral incorporated in the unit which is required by UL". Although it may not be "dangerous" by the letter of the law, my concern is that if someone should unknowingly receive this "tingle" the natural reaction is to pull away which has potential for injury. First, is this the "norm"? and How should a manufacturer of a piece of equipment which incorporates a UPS warn their customers of this? Anyone have experience with this? Thank you in advance, Lisa --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
