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What is over fluxing relay?
Over Fluxing relay is used to protect the generator against overheating and the winding insulation failure. Over fluxing protection is a popular protection in transformers, which is mainly used in power transformer.
What is over fluxing protection?
The over fluxing protection operates when the ratio of the terminal voltage to frequency exceeds a predetermined setting and resets when the ratio falls below 95 to 98% of the operating ratio. By adjustment of a potentiometer, the setting is calibrated from 1 to 1.25 times the ratio of rated volts to rated frequency.
What is over excitation of transformer?
Overexcitation of a transformer means that the magnetic flux in the core is increased above the normal design level. This means that the voltage must be gradually increased, with increasing frequency, in order not to overexcite the transformer.
What is over fluxing in generator?
Over-fluxing occurs when a generator or a transformer is subjected flux levels which are above the permissible limits. Over- fluxing can occur when a generator or transformer is made to: (a) produce rated voltage at below rated speed (frequency). ( b) produce greater than rated voltage at rated speed (frequency).
What is over fluxing?
Abstract: In transformer over fluxing is the dangerous situation in which magnetic flux density increases to extremely high level. The high flux density increases core loss which may lead to overheating of components which in turn may result into internal fault.
What do you mean by over fluxing or over excitation What is the significance of the V F ratio?
When a transformer core is overexcited, the core is operating in a non-linear magnetic region, and creates harmonic components in the exciting current. A significant amount of current at the 5th harmonic is characteristic of overexcitation. Assuming Number of turns constant, Flux is directly proportional to V/f.
What is over excitation and under 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 normal excitation?
Synchronous motor excitation refers to the DC supply given to rotor which is used to produce the required magnetic flux. The field current, which causes this unity power factor is called normal excitation or normal field current.
What is excitation EMF?
The process of generating a magnetic field by means of an electric current is called excitation. Field coils yield the most flexible form of magnetic flux regulation and de-regulation, but at the expense of a flow of electric current.
Why are over fluxing relays used in Transformers?
Over Fluxing relay is used to protect the generator against overheating and the winding insulation failure. Over fluxing protection is a popular protection in transformers, which is mainly used in power transformer. Principle of Over fluxing relay operation:
What does over fluxing mean in a generator?
Coming to the generator the EMF is depending on the Excitation of field winding and the frequency is depending on the speed of the alternator. The relay is designed to monitor the ratio of voltage/emf to frequency. Increasing the ratio of v/f is called over fluxing.
When to use over fluxing or over excitation protection?
Generator Over Fluxing or Over Excitation Protection 24 G Over Fluxing or Over Excitation Protection 24 G. Over Fluxing relay is used to protect the generator against overheating and the winding insulation failure. Over fluxing protection is a popular protection in transformers, which is mainly used in power transformer.
What is the magnetic flux density of a transformer?
I.S. specification for electrical power transformer does not stipulate the short time permissible over excitation, though in a round about way it does indicate that the maximum over fluxing in transformer shall not exceed 110%. The magnetic flux density is, therefore, proportional to the quotient of voltage and frequency (V/f).