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Why it is necessary to disconnect the load when change the tap?
when the load is connected to draws some current. while changing the tap of the transformer the tappings related to the winding is changed , so the load current affects the transformer. hence while changing the tap it should be noted thatAnswerThere are two types of tap-changing mechanism -'off-load' and 'on-load'. Off-load tap changers physically disconnect the winding when changing from one tap setting to the next. Accordingly, the circuit is temporarily broken, and dangerous arcing will take place if the transformer is energised. Therefore off-load tap changers require that the transformer is disconnected while the mechanism is operated.On the other hand, 'on-load' tap changers use a mechanism which incorporates a 'make before break' contact arrangement, ensuring that no break is made in the circuit as the mechanism moves from one tap setting to the next, enabling it to operate with the transformer energised and supplying load. On-load tap changers are usually automatically operated, although this feature can be overridden and operated manually.
How does on load tap changers operate?
On-load tap-changers are operated by an electric motor, often by driving a flywheel mechanism. The operation of the tap-changer is controlled by an AVR (automatic voltage regulator) which monitors the transformer's secondary voltage.
Why tapping are provided in high voltage winding of transformer?
Tappings are provided in order to make small adjustments to the turns ratio, so that the secondary voltage can be increased or reduced, if required, in order to meet the relevant statutory voltage variation requirements.Tap changing mechanisms may be 'off-load' or 'on-load' types.With off-load tap changers, the transformer must be de-energised before the tap-changing mechanism is altered, as the mechanism breaks the connection to the windings as it is changed.With on-load tap changers, the mechanism is adjusted (usually automatically, when required) with the transformer energised and supplying load. The mechanism is installed on the high-voltage side of the transformer (regardless of whether it is a step up or step down transformer) because the high-voltage windings carry the lower current, allowing smaller contacts to be used. On-load tap changers use a 'make-before-break' arrangement, so that the windings are never disconnected when the mechanism changes its tap setting.
What is the use of tap changing switch?
To make minor adjustments to the transformer's turns ratio in order to slightly increase or decrease the secondary voltage in order to maintain that voltage within legal requirements. Off-load tap changers, as the name implies, can only be operated when the transformer is disconnected.
How is current controlled in welding transformer?
in welding machine, the transformer used is basically a current transforrmer. so by changing the tap of secondary side of transformer, we can increase or decrease the current in the transformer.
What is off load tap change?
Tap changer is a device that is used to change the secondary voltage on transformers. It is normally on the HV winding of the transformer. Off load tap changer is designed to change the taps only when the transformer is not charged, while on load tap changer is capable of changing the tap on load too.
Why tapping is necessary in a transformer?
Taps are connections to the (usually) high-voltage winding of a transformer which enables minor changes to the turns-ratio to be made in order to make minor changes to the secondary voltage to compensate, where necessary, to a fall in terminal voltage below the regulatory allowance.There are two types of tap-changing mechanism, 'off-load' and 'on-load'.Off-load tap-changing mechanisms require the transformer to be isolated before its tap settings can be adjusted, and is normally the case with smaller distribution transformers.On-load tap-changing can be performed with the transformer supplying its load, usually automatically, in response to changes in its secondary voltage. On-load tap changing mechanisms have a 'make before break' switching arrangement, to ensure that the transformer windings are not open circuited during the operation of tap changing.
What would an off load transformer tap changer be used for?
to inreases or decreases n. of turns of a transformerAnswerAn 'off-load' tap changer is a tap-changing mechanism that can only be used when the transformer is disconnected, as opposed to an 'on-load' tap-changing mechanism that can operate when the transformer is energised and on load.Tap changing is performed to slightly change the turns ratio of a transformer in order to keep the secondary voltage within the statutory limits (e.g. in the UK, 230 V +10% -6%) should there be a substantial change in load.
Why it is necessary to disconnect the load when change the tap?
when the load is connected to draws some current. while changing the tap of the transformer the tappings related to the winding is changed , so the load current affects the transformer. hence while changing the tap it should be noted thatAnswerThere are two types of tap-changing mechanism -'off-load' and 'on-load'. Off-load tap changers physically disconnect the winding when changing from one tap setting to the next. Accordingly, the circuit is temporarily broken, and dangerous arcing will take place if the transformer is energised. Therefore off-load tap changers require that the transformer is disconnected while the mechanism is operated.On the other hand, 'on-load' tap changers use a mechanism which incorporates a 'make before break' contact arrangement, ensuring that no break is made in the circuit as the mechanism moves from one tap setting to the next, enabling it to operate with the transformer energised and supplying load. On-load tap changers are usually automatically operated, although this feature can be overridden and operated manually.
Why there is a need to disconnect transformer while using off-load tap changer?
Changing off-load tap changers requires opening up the transformer, draining (at least some) oil, and manually changing electrical connections. None of these things can be done while the transformer is hot.
Difference between off load transformer and on load transformer?
Hope this helpsAn "OFF-Load tap transformer" can only have it's tap adjusted when it is De-energized,while the "On-Load tap transformer" can adjust its tap under load conditions.Kind RegardsHammad KhanUniversity of Western AustraliaAnswerAn 'off load' transformer is one whose secondary is open circuited, and not supplying a load. An 'on load' (not 'load') transformer is one that is connected to a load.
What is the problem of operating a on-load furnace transformer with center tap?
What is the problem of operating a on-load furnace transformer with center tap
What is on load tap chenger?
A tap changer is used to vary the turns ration between the windings of a transformer to make minor changes to the secondary voltage. An on-load tap changer enables the turns ratio to be altered without disconnecting the transformer. An off-load tap changer requires the transformer to be temporarily diconnected. On-load tap changers are installed on the high-voltage side of the transformer, where the current is lower.
What are the types of tap changing transformer?
The simplest type of tap-changing mechanism is a rotary switch which allows the distribution company to select one of several 'tapping' (connection) points on the high-voltage side of a transformer. This enables the turns-ratio of the transformer to be adjusted to slightly elevate or reduce the output voltage if required. This type of tap changer is termed an 'off-load' tap changer, because it cannot be operated when the transformer is energised because the winding is temporarily disconnected as the mechanism's contacts move from one tap to the next. Off-load tap changers are operated manually, using a handle located outside the transformer -after the transformer has been de-energised, isolated, and safety earths (ground) applied.More complicated is the motor-driven 'on-load' tap-changing mechanism. It, too, alters the turns-ratio of a transformer, but this is done (usually) automaticallyaccording to changes in load. Unlike the 'off-load' mechanism, the high-voltage winding is never temporarily disconnected as the mechanism's contacts move from one tap to the next. This is because a pair of contacts is involved. One contact moves to the new tap position while the second remains at the first tap connection; when this has been done, the second contact follows the first onto the new tap position -so there is no break in the circuit. Additionally, there might be surge-suppressors fitted, to limit current surges during the tap-changing operation.Tap changers are always fitted to the high-voltage windings, where the current is lower -thus enabling smaller contacts to be used.
When operating a no load tap changer on a transformer what should be done first?
First isolate the transformer
Why was the tap changing panel removed from a transformer?
So that tap-changing can't be done any more, or maybe the tap changer was faulty.
What is on-load tap-changing?
On-load tap-changing is done in electric power supply systems to maintain the supply voltage to customers within limits. Tapping is done by switching extra turns in or out, usually on the high-voltage winding of a transformer. The switching is done by a make-before-break switch to avoid excessive sparking in the transformer, and this enables the switching to be done without interrupting the supply.
