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Who controls the excitation voltage and modifies the excitation?

Author

David Richardson

Updated on March 20, 2026

Who controls the excitation voltage and modifies the excitation?

The DC excitation system has two exciters – the main exciter and a pilot exciter. The exciter output is adjusted by an automatic voltage regulator (AVR) for controlling the output terminal voltage of the alternator. The current transformer input to the AVR ensures limiting of the alternator current during a fault.

Hereof, which controls the excitation voltage?

The difference between detected voltage and given reference voltage is called as the error voltage. The regulator then controls the excitation voltage of the alternator to cancel out the error voltage. Thus, an automatic voltage regulator controls the voltage by controlling the excitation.

Secondly, how does an excitation system work? The excitation system creates the electromagnetic field in the rotor. The stator has the armature winding that has the electrical energy induced. The stronger the magnetic field created, the stronger the electrical power produced. The strength of the magnetic field is adjusted by controlling the current to the rotor.

In this regard, what is used for excitation control?

Excitation systems use closed-loop or feedback control to regulate the machine's output. In closed-loop control, the machine output is routed back to the controller and compared to a setpoint, and the error between the setpoint and output is used to compute the system response.

How do you control the output voltage of a generator?

9.5 Excitation and Voltage Regulation

The output of a generator is normally controlled by controlling the current in the field of the generator, the speed being constant for a set frequency.

Why is excitation always DC?

In the alternator, as the rotor conductor changes its position as the rotor rotating so constant flux is to be produced in the rotor winding and it is possible only when the DC supply is given to the rotor winding. As we need constant flux that is why DC is used instead of AC for excitation of Synchronous Alternator.

Why is excitation voltage DC?

Why only D.C is used for Excitation in Alternators? Excitation voltage or current is supplied to the field windings of a rotor to produce a static magnetic field. If we use alternating current instead of direct current; we will get a fluctuating magnetic field.

Why is excitation needed?

An excitation system is necessary since, without excitation current, the machine operates without field current and consequently, no voltage is generated (induced) in the stator windings of the machine.

Which is most effective voltage control method?

Power Factor Correction Circuits

As the inductor voltage is sensitive to the phase shift Ï•, but not sensitive to the change in magnitude of reference, the inductor voltage control method is more effective in keeping the line current in phase with the line voltage.

Does alternator need excitation?

Without the excitation system the AC alternator would have no way of building its voltage as it starts to rotate, nor would not be able to regulate its voltage to the pre-set nominal level while running at its rated speed. So, without an excitation system, an AC alternator would be useless for its purpose.

What is excitation current?

Excitation current is the current flowing into the high voltage winding with the low voltage side open. This current should be proportional to the No-load acceptance test but with the difference resultant from the use of test voltages different from nominal values.

What are the types of AVR?

There are two types of automatic voltage regulators. There are two types of motor, the Relay type and the Servo Motor type. Relays and semi-conductors are used to regulate the voltage in a Relay type AVR.

What are the requirements of AVR?

The AVR shall be provided with an integral, three pole, molded case, manually operated, thermal magnetic input circuit breaker rated at 125% of the full load input current. In addition, the system input current, Phase A, B and C, shall be monitored and digitally displayed.

What are the types of excitation methods?

Excitation methods include:
  • Self-excited (shunt)
  • Excitation boost system (EBS)
  • Permanent magnet generator (PMG)
  • Auxiliary winding (AUX)

What is excitation in psychology?

n. the electrical activity elicited in a neuron or muscle cell in response to an external stimulus, specifically the propagation of an action potential.

What is separate excitation?

: having the field magnets excited by a current from a separate source —used of a machine.

What is PMG excitation?

The PMG (Permanent Magnet Generator) is a system which is used for secondary exciting. The PMG provides stable and reliable electric energy for AVR regardless the generator's terminal voltage. The generator with PMG excitation system can provide 300 % rated current during short-circuit, which occurs for 5-10 seconds.

What is the function of exciter in excitation system?

A Exciter. The exciter supplies direct current to the field winding of the generator, at whatever voltage is required to overcome the resistance of the winding.

Why AVR is used in generator?

What is a Generator Automatic Voltage Regulator? An automatic voltage regulator (AVR) is a solid state electronic device for automatically maintaining generator output terminal voltage at a set value. It will try and do this as the generator load or operating temperature changes.

What are the characteristics of an excitation system?

The dynamic characteristic of the excitation control system refers to the transient process when, in response to an external disturbance (such as a sudden change in the reactive load) or a change in the setting value, the system transits from a stable state to another state at this moment.

What happen when generator loss excitation?

When a generator loses its excitation, the rotor current decreases gradually and the field voltage slowly decays as dictated by the field time constant. As a final outcome, the generator starts to consume reactive power from the power system instead of supplying it.

What do you mean by excitation?

excitement

What is the function of exciter?

The main purpose of exciter in a generator(alternator) is to provide stationary rotating magnetic field. Which is used to induce the e.m.f in the armature coil. So, DC power is given to exciter and the exciter is nothing but a coil, and the exciter creates a magnetic field.

What is under excitation and over excitation?

The over-excitation limiter protects the generator against over-temperature caused by high field current for long time. Under-excitation limiter prevents the decrease of generator field current to the values lower than the stability margin or the thermal limit of end side of the stator core.

What is excitation test in transformer?

excitation test represents the iron core saturation. This test is performed by applying a sinusoidal voltage (V2) in the secondary winding while the primary winding is opened, as shown in the Figure 5. The injected voltage produces a magnetic flux in the core, and the value of the rms current should be recorded.

What controls the speed of a generator?

Droop speed control is a control mode used for AC electrical power generators, whereby the power output of a generator reduces as the line frequency increases. It works by controlling the rate of power produced by the prime mover according to the grid frequency.

How do you adjust the voltage on a generator?

Adjust the throttle of the generator to increase or decrease RPMs of the machine's motor. Slowing the RPMs decreases the voltage output; increasing RPMs increases the voltage output. The throttle is normally located on the top or side and has RPM written on it.

What happens if voltage is too high?

Voltage that is too high can cause premature failure of electrical and electronic components (e.g. circuit boards) due to overheating. The damage caused by overheating is cumulative and irreversible. Motors can, on the other hand, often benefit from voltages that tend to be a little bit high.

What factors control generator output?

The amount of output voltage produced by the generator is proportional to three factors:
  • the number of turns of wire in the armature.
  • the strength of the magnetic field of the pole pieces.
  • the speed of the cutting action (speed of rotation)

What are the three 3 basic types of voltage regulators?

There are three types of Switching voltage regulators: Step up, Step down, and Inverter voltage regulators.

How many ways can the voltage of a generator be regulated?

For large alternators, the three indirect methods are used to determine the voltage regulation they are as follows: Synchronous Impedance Method or EMF method. Ampere-turn method or MMF method of Voltage Regulation. Zero Power Factor method or Potier Method.

What causes a generator to produce high voltage?

If the generator engine speed is unstable that means too high, then the voltage increase significantly. If working load is exceed than the generator efficiency, and then the voltage will be unstable. Sometimes voltage regulator components become hampered. On that occasions, voltage increases.

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Who controls the excitation voltage and modifies the excitation?