The alternator rotor could be considered the heart of the alternator. Without it functioning properly the alternator would not operate correctly. The rotor has a very important role as a component of the alternator. Therefore, for the most part this article will examine the alternator rotor.
The alternator rotor consists of the:
- rotor shaft,
- rotor winding,
- two claw-shaped finger north and south magnetic poles,
- two slip rings,
- and, in some applications, the internal cooling fan and support bearings.
The rotor shaft is a machined and balanced steel rod which accommodates the rotor winding, two claw-shaped finger north and south magnetic iron poles, slip rings, and, in some applications, the internal cooling fan and support bearings. The rotor shaft is supported by the front and rear alternator housings by means of bearings or bushings. The shaft also allows for installing internal or external cooling fans and the alternator pulley. Rotor shaft failures could be mushroomed ends, and bent or broken shafts.
The rotor winding is a small gauge copper wire wound in several loops around an iron core which is usually part of the two claw-shaped finger north and south magnetic iron poles. Or, the winding may be wound on a separate iron core which would then be sandwiched between the magnetic pole halves and
press fit on the rotor shaft. The ends of the rotor winding are attached to the slip rings by soldering. The rotor winding is sealed and insulated from the iron core using usually epoxy glass resin. Rotor winding failures could be burnt windings, windings shorted to metal or broken windings.
The pole pieces can either be cylindrical, oval, or ball shaped malleable iron cut in half in a zigzag pattern creating usually six or more fingers and hallowed out to accommodate the rotor winding. The pole pieces are press fit onto the rotor shaft on each side of the rotor winding with the fingers meshing but not touching creating north and south poles. Pole failures could be looseness on the shaft or unwanted contact to another component.
The slip rings are copper collar shaped rings that are press fit on the rear portion of the rotor shaft behind the rear pole piece. Each ring is soldered to one end of the rotor winding. The slip rings provide a means for a moving electrical circuit to connect to a stationary electrical circuit. The slip rings are insulated from each other, the rotor shaft, and pole pieces. Slip ring failure could be pitted, burnt, or glazed contact surfaces.
The alternator rotor, depending on application, may have support bearings and cooling fans on the rotor shaft.
As always, if any procedure in this series of articles appears to be beyond the capabilities of the vehicle owner or driver, then testing and servicing the alternator should be performed by a professional or ASE Master Certified mechanic. The vehicle would have to be taken to a repair shop that employs these types of mechanics such as A & M Alternator Services located at 2419 E. Jackson St. in Phoenix, Auto Electric Specialists located at 5216 W. Lamar Rd. in Glendale, Village Auto Electric Service located at 19 N. Miller St. in Mesa, All Start Electric located at 13501 E. Chandler Blvd. in Chandler, Jordan’s Automotive Specialists located at 8718 E. McDowell Rd. #3 in Scottsdale, Rob’s Quality Automotive located at 11801 N. Cave Creek Rd. in Phoenix, Scottsdale Pro Tech located at 8245 E. Butheruand Dr. #111 in Scottsdale, and Art’s Family Auto Repair located at 915 W. Hatcher Rd. in Phoenix.