Slip rings are used on what type of generator?

• A. AC generators and DC alternators
• B. DC motors
• C. AC motors
• D. All types of generators

Answer: (A)

Slip rings provide a continuous connection to a rotating winding, which is needed to excite the rotor field in machines with a wound rotor. For generators that rely on a rotating field, the rotor must be fed with DC to create and sustain the magnetic field while it spins. That excitation is supplied through slip rings and brushes, making them a key feature of AC generators (alternators) and DC alternators. In these machines, the rotor’s field current stays on the spinning part, while the output comes from the stationary stator. Other types of motors and generators typically use a different method for rotor excitation (or do not require a rotating field fed through slip rings), so slip rings are not used in those cases.