 
 <prompt> Wetin fit cause difference for power inside di building if dem no isolate di elevators? Based on di question wey dey before, write one context wey get di answer. E fit be 1 - 20 sentences. Context: <response>: Historically, AC motors dey use for single or double speed elevator machines sake of cost and lower usage applications where car speed and passenger comfort no too important, but for higher speed, larger capacity elevators, the need for infinitely variable speed control over the traction machine dey important. Therefore, DC machines wey dey powered by an AC/DC motor generator na the preferred solution. The MG set also dey typically power the relay controller of the elevator, wey get the added advantage of electrically isolating the elevators from the rest of a building's electrical system, so e dey eliminate the transient power spikes in the building's electrical supply wey dey caused by the motors starting and stopping (wey dey make lighting dey dim every time the elevators dey used for example), as well as interference to other electrical equipment wey dey caused by the arcing of the relay contactors in the control system. 