DS and ES Range

The DS and ES range of Ferranti Tapchangers (tap changers) are of the high speed resistor transition type, designed for continuous operation.

Description of Gear
The Tapchangers are designed to bolt directly onto the transformer tank. This range of Tapchanger is designed to operate with maximum currents of either 300, 400 or 500 amps with a maximum working voltage of 36kV or 72.5kV. Insulation class test voltages are 70kV or 140kV to earth and they provide a maximum of 16 tapping steps 17 tap positions. read more.... The ES3/19 Ferranti Tapchanger can be provided with 18 tapping steps 19 positions. Also the DS range can be modified to operate with working voltages up to 44 kV. The DS range of Ferranti Tapchangers (tap changers) have combined diverters and selectors housed in one compartment, with motor drive and timing gear in a separate compartment on the front. The two compartments are sealed from each other and the transformer tank, and are independently oil filled, keeping to a minimum the amount of oil required for any inspection and maintenance. Oil drain and filler valves are provided for each compartment.

Connections for the transformer tapping winding are made directly on to the rear of the fixed selector switch contacts, which extent through the rear of the circular moulded switch bases, these bases also perform the function of barrier panels or barrier board. Oil contamination between the Tapchanger (tap changer) and transformer is thus eliminated and makes the Tapchanger an independently sealed unit.

The front oil filled housing contains the single phase driving motor, the operation of which is initiated by means of push buttons or directly from contacts of the voltage control relay, subsequently causing directional and maintaining switches to close and secure the motor supply independently of the initial signal to ensure a complete tap change.

The drive is taken by the chain through a reduction mechanism to charge the stored energy device, which ensures that the tap change switch cannot stop between taps should the supply to the motor drive fail.

On release the device drives a Geneva mechanism, coupled through into the rear compartment to drive an insulated gear train and the selector switch assemblies. The front compartment also contains the timing, sequencing and motor control on printed control boards or printed circuit boards and is mechanically coupled to the drive system to ensure correct indexing and control over the complete tapping range. A tap position indicator and operations counter are visible through a sight glass window in the front of the housing.

The units are fully equipped to be capable of integration into most control schemes without additional contractors. Printed control boards, printed circuit boards proved auxiliary contacts as required, for example, remote tap indicator. A variety of printed circuit boards are available to suit any automatic and or parallel control schemes into which the units may be integrated. Connections for external control of the Ferranti Tapchanger are made to easily accessible terminals at the side of the drive mechanism compartment. Optional local electrical control can be provided on the Tapchanger or may be incorporated in the transformer control cubicle or marshalling kiosk. Individual schematic and wiring diagrams are provided for each order. The scheme chosen dictating the printed circuit board and any associated equipment required.

The rear compartment also houses the three single phase selector switch moving contact arm assemblies, each moving contact assemblies carry a bridging resistor, transitional arcing contacts and the main current carrying contact. The fixed selector switch contacts are mounted radially in the three circular insulated switch bases, barrier boards, these contacts are cylindrical in shape and have separate arcing contacts fitted. The contacts are made of a specially developed alloy for long life and electrical arcing properties.

An oil expansion chamber is located at the top of the switch compartment complete with gas release valve. An oil surge relay and low level relay and a silica gel breather are fitted as standard on the ES units but are optional extras on the DS range.

The timing equipment is in the form of printed circuit boards operating with plunger contact connection boards. The auxiliary switch printed control board turns once through 360 degrees every tap change and is fitted to all Ferranti Tapchangers in the range. The step switch printed circuit board is interchangeable and tailored to the scheme required.

DS and ES range of Ferranti Tapchangers are suitable for linear applications and are capable of reverse direction power flow within limits.