The whole European S ratings are a gimmick for marketing, but they can sell a motor that¡¯s S6 on the saw because saws are very rarely running at full load unless it was some automated rip saw that was being power fed continuously. Dust collectors and compressors run at full load all the time, so they get S1 motors.
Here in the US, we rate motors at HP and then give them a duty rating. A 4hp 100% duty rating motor will put out 4hp continuous without overheating and toasting the windings. If you have an occasionally intermittent overload, you might want to spec a 4hp motor with a 135% duty rating, which means it can effectively run at 35% over 4hp continuously without toasting the windings. It¡¯s all about heat dissipation without breaking down the insulation on the windings.
It¡¯s kind of a six of one, half dozen of the other way of looking at things. It just seems a little more upfront with the US ratings because your motor will never be less than the stated hp regardless of the duty rating, where the European standard allows them to call a motor 5hp but you can only fun it at that 60% of the time and it¡¯s actually only a 4hp continuous motor.
Brian Lamb
blamb11@...
www.lambtoolworks.com
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On Aug 17, 2020, at 8:41 AM, imranindiana via groups.io <imranindiana@...> wrote:
Brian,
¡°the S1 3hp motor is the same as a S6 4hp motor¡±
i have read this before. i believe this means that a 4hp motor can be sold as s6 or as derated 3hp-s1.
i can see the 3hp-s1 derating work in an application like a compressor where the manufacturer knows that load will not exceed 3hp but how does it work when load is user controlled and in many cases impossible to know, e.g. sawing.
maybe, the derating of motors is only done in applications with known load. i would think dust collector is such application. max load of unrestricted operation is hard to exceed.
just thinking.
imran
