 
 <prompt> Wetin be di ideal source of power? Based on di previous question, write a context wey contain di answer. E fit be 1 - 20 sentences. Context: <response>: "A PM motor no get field winding for the stator frame, instead e dey rely on PMs to provide the magnetic field wey the rotor field go interact with to produce torque. Compensating windings wey dey in series with the armature fit dey used for big motors to improve commutation under load. Because this field dey fixed, e no fit adjust for speed control. PM fields (stators) dey useful for small motors to eliminate the power wey the field winding dey consume. Most big DC motors na "dynamo" type, wey get stator windings. Historically, PMs no fit retain high flux if dem disassemble; field windings dey more practical to get the amount of flux wey dey needed. However, big PMs dey expensive, as well as dangerous and difficult to assemble; this dey make wound fields dey preferable for big machines." 