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synchronous machine[′siŋ·krə·nəs mə′shēn]
an AC machine (usually three-phase) whose rotational speed n is proportional to the frequency of the power circuit. The relation between n and f is given by the equation n = f/p, where P is the number of pole pairs in the machine.
Depending on how they are operated, synchronous machines are classified as synchronous generators (generators of active power), synchronous motors (motors with a constant rotational speed), and synchronous condensers (generators of reactive power). A synchronous machine can perform any of these three roles. In practice, however, present-day synchronous generators, motors, and condensers have certain design differences.
The principal components of a synchronous machine are a stator and a salient-pole or nonsalient-pole rotor. The stator has an AC winding. The rotor winding is the field winding and is always supplied with direct current through slip rings. Sometimes in low-power (up to 20 kilowatts) machines, the AC winding is placed on the rotor, and the field winding on the stator. This type of machine is said to be of inverted design.
REFERENCESPetrov, G. N. Elektricheskie mashiny, part 2. Moscow-Leningrad, 1963.
Kostenko, M. P., and L. M. Piotrovskii. Elektricheskie mashiny, 3rd ed., part 2. Leningrad, 1973.
Vol’dek, A. I. Elektricheskie mashiny, 2nd ed. Leningrad, 1974.
M. D. NAKHODKIN