Ans. Usually from five to ten seconds.
Ques. How is the starting lever operated?
Ans. It is moved progressively from contact to contact, pausing long enough on each contact for the motor to accelerate its speed before passing to the next.
Ques. What are the conditions at starting in a series motor?
Ans. There is a rush of current, the magnitude of which depends on the amount of resistance cut out at each movement of the starting lever.
Figs. 737 and 738.--Sliding contact starters. [Fig. 737], starter with button contacts; [fig. 738], starter with renewable contacts. Motor starters in which the successive steps of resistance are cut out by a pivoted lever carrying a contact shoe which slides over button contacts or over contact segments, are known as sliding contact starters. Button contacts are usually furnished with motor starting rheostats of small size while contact segments are used on those of greater capacity. The contact segment being held in position by two screws, is readily renewable when worn by long service or damaged by arcing. The fixed button contact is not so easily renewed but being used only on small size starters is never likely to be subjected to severe service. Some starters, however, have renewable button contacts.
Ques. How are small series motors started on battery circuits?
Ans. By simply closing a switch to complete the circuit, the resistance of the battery being sufficient to prevent a great rush of current while starting.