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What is open circuit test in alternator?
When an alternator delivering full rated output voltage is suddenly subjected to a short-circuit, very large currents will initially flow. The open-circuit test or the no-load test, is performed by driving the generator at its rated speed while the armature winding is left open.
What is open circuit characteristics of alternator?
Thus Open Circuit Characteristic or OCC is basically the plot between the armature terminal voltage Ef versus field current If while keeping the speed of rotor at rated value. Figure below shows the connection diagram for performing the Open Circuit Test of Alternator.
What is OCC and SCC?
Open circuit characteristic (OCC) and Short Circuit Characteristics (SCC) of a Synchronous generator.
Why it is called OCC of the alternator?
Characteristics of DC Series Generator The curve AB in above figure identical to open circuit characteristic (O.C.C.) curve. This is because in DC series generators field winding is connected in series with armature and load. Hence, here load current is similar to field current (i.e. IL=If).
What is short circuit test of alternator?
The short-circuit test provides information about the current capabilities of a synchronous generator. It is performed by driving the generator at its rated speed when the terminals of the armature winding are shorted. An ammeter is placed in series with one of the three shorted lines.
What is EMF method?
The Synchronous Impedance Method or Emf Method is based on the concept of replacing the effect of armature reaction by an imaginary reactance. The method requires following data to calculate the regulation.
What do you mean by the short-circuit characteristic of an alternator?
SHORT CIRCUIT CHARACTERISTICS OF AN ALTERNATOR The three terminals of the armature are short circuited . The machine is driven at approximately synchronous rated speed and measurements of armature short circuit currents are made for various values of field currents usually up to and above rated armature current.
What is the power factor of alternator on short circuited condition?
Assuming load will be maximum in Short Circuit Conditions, the slip of the alternator falls on the negative, thus acting as an induction generator. The power factor will be lagging completely since the current drawn will be very high, the voltage will fall below the rated voltage of the alternator.
Why do we perform short-circuit test for the synchronous alternator?
When short circuited, armature reaction prevents the machine from saturating. The short-circuit per-phase equivalent circuit and phasor diagrams are shown below. Synchronous reactance is usually significantly larger than armature resistance. As a result, the armature current significantly lags the induced voltage.
What is EMF equation of alternator?
V = 4.44 Kf KC KD f ΦT Volts. Where: V = Actual generated Voltage per phase.
What is difference between EMF and MMF?
When there is a current flow through the conductor coil, a force is produced to drive the magnetic flux or magnetic field lines. This force is called MMF or magnetomotive force. The EMF or electromotive force is the force responsible for the flow of electrons or current in a closed circuit.
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