# Synchronous generator

Apr. 9, 2018
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### Synchronous generator

• 1. Electrical power system Synchronous Generator (Alternators) By:-Abhishek kumar
• 2. Introduction:- • Ac generators are usually called alternators. They are also called synchronous generators • Rotating machines that rotate at a speed fixed by the supply frequency and the number of poles are called synchronous machines • A synchronous generator is a machine for converting mechanical power from a prime mover to a.c. electric power at specific voltage and frequency. • Synchronous machine are used primarily as
• 3. Construction of Three-phase Synchronous Generator:- • An Alternators consists of two main parts namely , the Stator and Rotor. • The Stator is a stationary part of the machines. It carries the armature winding in which the voltage is generated. The output of the taken from the stator. • The Rotor is the rotating part of the machines. The rotor produces the main field flux.
• 4. Diagram of 3-Phase Synchronous Generator:-
• 5. Speed And Frequency:- Frequency:- P=total number of poles N=speed of field poles in r.p.m. n=speed of field poles in r.p.s. f=frequency of the generated voltage in Hz. N/60 = n P/2=p f=PN/120
• 6. Synchronous Speed:- • Synchronous speed Ns = 120f/p Where Ns is the called synchronous machine f = frequency the generated voltage in Hz P = total no of field poles
• 7. Advantage of Synchronous generator:- • In synchronous motor the speed remains constant irrespective of the loads. • Synchronous motors can be constructed with wider air gaps than induction motors which makes these motors mechanically more stable. • In synchronous motors electro-magnetic power varies linearly with the voltage.
• 8. Disadvantage of synchronous Generator:- • Synchronous motors requires dc excitation which must be supplied from external sources. • The cost per kW output is generally higher than that of induction motors • Synchronous motors cannot be started on load. Its starting torque is zero • When loading on the synchronous motor increases beyond its capability, the synchronism between rotor and stator rotating magnetic field is lost and motor comes to halt .