Motors with brushes are "incidental radiators" according to the FCC. I
believe PWM or variable frequency drive motors would be considered
"unintentional radiators" in that they intentionally generate a radio
frequency (9 kHz to 3,000,000MHz) but do not intend to radiate it. (see
definitions at http://www.hallikainen.com/FccRules/2007/15/3/).

Incidental radiators must use good engineering practice to minimize
interference (see http://www.hallikainen.com/FccRules/2007/15/13/).

Digital devices (I think motor control systems qualify as digital
devices) in appliances are exempt from the emission limits for
unintentional radiators (see
http://www.hallikainen.com/FccRules/2007/15/103/), though the user must
cease operation if the FCC finds it is causing interference.