motor overloads standards
motor overloads standards
(OP)
I am looking for any standardized information on overloads motors should withstand relatively to their power rating.
Is there any norm or admitted standard about that ?
Thank you
Is there any norm or admitted standard about that ?
Thank you





RE: motor overloads standards
The fact that NEMA also allows the standard motor to operate at a voltage up to 10% low would seem to imply to me that NEMA is suggesting motors contain at least 10% overload capability.
Motor overload protective settings for 49 device are typically in the range of 115%-125%FLA and higher for service-factor rated motors. Some info in IEEEC37.96 section 7.2.9.1. I'm not sure exactly where these numbers originated, it may be the NEC.
The motor purchaser can request from the manufacturer a thermal damage curve IAW IEEE620-1996 which will define exactly how much time is allowed for any given level of overload. Alternatively if the motor is required to have a known short-time duty above rated, the user can make this part of his specification.
RE: motor overloads standards
RE: motor overloads standards
I would also like to add that the report from GAMBICA for vfd's is really good as far as insulation stresses for motors including NEMA MG1 pt 31 and IEC 60034-17 (the other motor standard that I see more and more these days.)
http://www.gambica.org.uk/newsite/public.html#g1
Carl