Greetings experts. This question applies to both North America rules (NEC) keeping in mind the rest of the world including Europe BUT my example will be for a 115Vac 60hz device.
My example product is used in the Workplace but not typically in an industrial environment (if that matters). It's not a home appliance or power tool. Consider an End Product powered by 115Vac 60hz from a standard 16AWG power cord with a NEMA-5-15 plug, from a 15 amp receptacle (15 amp Branch Circuit). Within this product is a 1/2 hp motor with an Full-Load Amp (FLA) rating of 5 amp. The motor can run continuous in this application. The motor does not have integrated over temperature protection. Scenario 1: If this was a single phase AC motor, we would have to provide Overload Protection. According to the NEC, a fuse or circuit breaker no larger than 6.25 amp (FLA x 125%) can be used (lets ignore start up current for now). Can this Overload Protector be a "Supplemental Protector" (UL 1077 circuit breaker) or does it have to be a UL 489 circuit breaker or some other type of device? Scenario 2: If an Inverter, Frequency Drive, PWM Motor Controller, etc. is used to drive an AC or PWM DC motor (1/2hp), the Branch Circuit is not stressed by Motor Start currents since the motor is soft started. So for example, if we have a 1/2hp 90Vdc motor that is driven by a PWM controller, can the Overload Protector be a Supplemental Protector? If not, what does it have to be and why? Scenario 3: If the inverter, frequency drive, PWN motor controller, etc. provides Overload Protection for the motor, do we even need to add an additional Overload protector? Can we use a single Supplemental protector for the entire product and not worry about the motor? In this scenario, I assume the motor controller would have to be Listed by a safety agency and specifically call out the overload protection feature in the datasheet. What other concerns might I need to know about? I'm trying to make sense of the NEC article 430 but it doesn't seem to address motors driven by Motor Controllers. Can I assume that when a motor is driven by a Motor Controller (inverter, freq. drive, PWM, etc.) that the NEC 430 does not apply because the motor is not being directly powered by a Branch Circuit? Thanks to all in advance. The Other Brian ________________________________ LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
