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Sections: Converters | Inverters | Starting | AC-to-DC

Synchronous Converters.

Definition. AC is supplied in the slip rings, DC field is excited. Armature rotaes as a synchronous motor. Brushes of the commutator are the terminals of a DC supply.

Applications. DC source for railways and industrial plants.

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Sections: Converters | Inverters | Starting | AC-to-DC

Synchronous Inverters

Definition. AC is taken from the slip ring, transforming DC to AC.

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Sections: Converters | Inverters | Starting | AC-to-DC

Synchronous Starting

a) DC STARTING - connected to a shunt motor. AC side is synchronized with the line like an AC generator and switched ON.

b) AUXILIARY MOTOR STARTING - a small induction motor or commutator AC motor to bring the converter up to above synchronuous speed. Motor is allowed to coast then synchronized with AC line.

c) FROM AC SIDE AS INDUCTION MOTOR - apply reduced voltage to the slip rings until up to speed. Shunt field circuit is closed. Apply full voltage.

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Sections: Converters | Inverters | Starting | AC-to-DC

AC-to-DC Conversion

Theory.
Source is an AC voltage which causes natural commutation, i.e.,
a. transfer of one current
b. transfer of voltage connection
c. sequential opening of one switch and closing the next

Circuits:
a. bridge (double-way)
b. mid-point (center-tap / single-way)
c. two-pulse midpoint
Operation. On positive half-cycle, transformer T1 and S1 carry load current, transformer T2 is reverse-biased. On negative half-cycle, transformer T2 and S2 carry load current, transformer T1 is reverse-biased.
d. three-pulse (with 3 thyristors)
e. six-pulse (with 6 thyristors)
f. 12-pulse (with 12 thyristors)

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