John, Heating of the contacts is one area of concern, but others come to mind readily namely heating of the branch circuit conductors and tripping of the branch circuit protector. There are other applications which operate with the same concept,, such as motors and incandescent lamps which have a high inrush currents at startup. The inrush in a motor is considered to be 6 times running current, and the circuit to which it is connected is developed to take this into account, I believe by using protection with time delay characteristics. The inrush in incandescent lamps can be 15 times steady state, which is taken into account while testing the devices which are used to control that load. I believe that the end use standard will govern the requirements (such as UL1950) rather than the standard for receptacles, because this is a problem of the end use situation. In my opinion, the duty factor will be the deciding factor on how the issue is resolved. "A few minutes per hour" does not give sufficient information. The chances are that the branch circuit protector will trip, to protect the branch circuit wiring, if the minutes all bunched up together, On the other hand, a second or two of high current, occurring at relatively large intervals, might be tolerated. I do believe that your best course will be to contact your friendly local certifying agency for a definitive opinion on this.
Gabriel Roy Hughes Network Systems The opinions expressed above are really off the cuff, may not be helpful at all, and are certainly not those of Hughes Network Systems. --------------- snip --------------------------------------------------------- I am testing a semi-portable instrument which is intended for sales into the international market. It uses an IEC320 high-current (cold) appliance inlet. When powered by 230Vac, the instrument always draws less than 15A from the mains. When powered by 120Vac, however, it normally draws 10A, but for short periods (a few minutes per hour of operation) will draw as much as 30A. Can anybody tell me which UL/CSA standards specify the current limits of appliance inlets? Do these standards preclude operation in excess of the 20A/125Vac limits, even for low duty cycles (I presume the limiting factor is heating of the contacts)? If so, can anybody suggest practical alternatives other than a bulky IEC309 connector or hard-wiring? Regards, John Quinlan [email protected]
