FIELD OF THE INVENTION

The present invention generally relates to tap changers connectable to Power transformers. More particularly, the invention relates to a device for displaying local and remote tap position for a tap changer operation to regulate output voltage of transformers.
BACKGROUND OF THE INVENTION
A Tap Count is a device used in a Motor Drive Unit of a Tap-changer and RTCC Panel. A tap changer is used in the power transformers in order to regulate the output voltage. The tap changer when electrically connected to the tap windings of a transformer is enabled to increase or decrease the transformer's output voltage by changing the tap position. The tap position is changed by a rotating shaft driven by the motor drive unit.
The tap changer varies the voltage ratio of the transformer by changing the turns ratio of the transformer by means of a combined operation of a tap selector, diverter switch and the motor drive unit. It is important to know the actual voltage ratio and the position of the tap selector so that the power transformer is not damaged by operating the tap changer beyond the end positions. A RTCC panel is used for controlling the movement of the tap changer from control room.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for displaying local and remote tap position for a tap changer to regulate output voltage of transformers, which eliminates the disadvantage of prior art.

Another object of the invention is to propose a device for displaying local and remote tap position for a tap changer to regulate output voltage of transformers, which is enabled to display the total number of tap change operations performed by the tap changer.
A further object of the invention is to propose a device for displaying local and remote tap position for a tap changer to regulate output voltage of transformers, which ensures that the tap changer is not operated beyond the end positions to avoid damage of the transformer.
SUMMARY OF THE INVENTION
The present invention replaces and/or adds following individual and essential components of prior art tap count device, for example:
(i) Tap position indicator is now enabled to display the local tap position number.
(ii) a Counter is provided for display of total number of tap change operation which was not available in prior art.
(Hi) A DC Transducer is arranged to provide dual output.
According to the invention, the tap count device is enabled to :
- display local tap position number;

- diagnose the highest tap position number and set the output accordingly, the highest tap position number being variable corresponding to different tap changes;
- indicate tap position at remote and SCADA application due to provision of means for dual DC current output;
- display the total number of tap change operations performed by the tap changer; and
- display the tap change position data even in case of input power failure, the data being stored in a memory of a non-resettable counter.
The special technical feature of the tap count device of the invention is its ability of displaying a local and/or remote tap position number including the total number of tap change operations performed i.e. the number of times tap position is changed apart from indicating DC Current output for remote tap position.
According to the inventions in the control unit of the motor drive unit, a plurality of resistance units are connected in series which is added or subtracted depending upon the increase or decrease in the number of tap positions.
The inventive device senses the resistance value as an input and display the input value as the tap position number for local use. The device records the number of times the value of resistance is changed and displays the number as a counter for tap change operation. It also converts the resistance value to DC current output for further use the

value in a remote and SCADA system. The device uses the same power source which are used by the control unit of the motor drive unit.
The present invention thus provides more functions/features in less space and eliminates various complicated prior art gear mechanism for tap position indication and counter operation of the prior art devices.
The device can be incorporated in RTCC Panel being used for control of transformer unit.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
Figure 1 - Schematically shows the operation of a tap changing device.
DETAIL DESCRIPTION OF THE INVENTION
Figure 1 shows a tap count device of the invention. As shown in figure 1, at least one input power supply terminal (IT) is connected to a source of 90-260 AC/DC, and generally 110V ac output of an Auxiliary transformer installed in a motor drive unit, (not shown)
A series of 1000/100 ohm * (n-1) steps resistance input signal (IS) from a resister unit is connected to terminal numbers 4, 5 and 6. At terminal number 4, starting point of the resistor unit is connected. At terminal number 5, a moving contact of the resistor unit shows instantaneous resistance value. At terminal number 6, the last point of the resistor unit is connected. A non- counter (c) with a front panel (D) is connected

to the Resistor unit including the means (transducer) for dual current output (DO) via an apparatus incorporated with a logic Rule (LR).

WE CLAIM :

1. A device for displaying local and remote tap position enabling a tap
changer to regulate output voltages of a transformer, the tap
changer having a motor drive unit and electrically connected to tap
windings of the transformer, the device is enabled to :
- display local tap position number;
- diagnose the highest tap position number and set the output accordingly, the highest tap position number being variable corresponding to different tap changes;
- indicate tap position at remote and SCADA application due to provision of means for dual DC current output;
- display the total number of tap change operations performed by the tap changer; and
- display the tap change position data even in case of input power failure, the data being stored in a memory of a non-resettable counter.

2. The device as claimed in claim 1, wherein the motor drive unit comprises a control unit and wherein a plurality of resistance units are connected in series, the number of resistance units depending corresponding to increase or decrease in the number of tap positions.
3. The device as claimed in claim 1, wherein the input value of the device constitute the resistance value which are converted and displayed as the counter for tap change operation.

4. The device as claimed in any of the proceeding claims, wherein the plurality of resistance units are each collected to corresponding number of terminals of the device.
5. The device as claimed in any of the proceeding claims wherein a non-counter is connected to a front panel of the device.
6. The device as claimed in any of the proceeding claims, wherein the resister units comprises a transducer for dual current output in a logic rules incorporated therein.