Fig. 2,437.—Diagram of connections for Westinghouse dial type variable ratio voltage transformer. In construction the secondary winding of the transformer is divided into 10, 14, or 20 parts giving 11, 15, or 21 taps which are brought out from the secondary winding and connected to the various points of the dial. The diagram shows connections for an 11 point dial and regulating transformer. Since there is a difference of voltage between adjacent contacts, the contact arm must not touch the contact toward which it is moving until after it has left the contact upon which it was resting. Moreover, it is undesirable to open the circuit each time in moving from one contact to the next. These conflicting requirements are met by the use of arcing tips which are placed on the contact arm so that a very close adjustment can be obtained, and so arranged that the contacts are not short circuited but always have a gap of from one-sixteenth to one-eighth inch in the circuit during the time of changing from one contact to the next. The air gaps form a "preventive resistance." A quick moving mechanism is used to accelerate the movement from one contact to the next, a very quick movement being necessary to avoid undue arcing. The capacity of the regulator is 200 amperes at 2,200 volts, being arranged to give a maximum increase in voltage of 400 volts. The maximum pressure between contacts is 25 volts.
Fig. 2,438.—Diagram of connections of General Electric pole type regulator. The operation of the regulator is obtained by means of a small single phase motor which is in continuous operation, and which by mechanical means may be connected to the regulator shaft. The control of the mechanism is obtained by means of a voltage relay. The operating motor, which is of the drawn shell type, is provided with a starting clutch and will consequently start up with full load. Under actual operating conditions it will, of course, be comparatively seldom that the motor will be called upon to start up. A non-inductive resistance, made up from standard units, is connected in series with the relay winding and several taps are provided, so that the relay can be adjusted for any voltage from 10 per cent. below normal. In order to readily dissipate the heat developed in the resistance, it has been mounted in a pocket on the back of the tank, openings being provided for natural air ventilation. The relay plunger is hinged to one end of a balance arm, which arm is provided with two trip pins to control the mechanism. An adjustable helical spring is attached to the other end of the arm to assist the magnetic pull of the coil in balancing the plunger and also for adjustment. The relay is not provided with series winding for line drop compensation, but it may be used with a standard line drop compensator, which then has to be installed outside of the regulator. The voltage relay must be connected to the feeder side of the regulator, the necessary low voltage to be obtained from a distributing transformer, or if this should not be available in the immediate vicinity, a 200 watt step down transformer will be satisfactory. The motor is designed to operate in parallel with the relay, the normal connections being as shown. The speed of the motor and the ratio of the gearing is such that it requires about 90 seconds to operate the regulator from limit to limit, but, as this regulator is not intended to take care of sudden voltage fluctuations, the comparatively long time of operation will not be objectionable.
Figs. 2,439 to 2,443.—General Electric pole type regulator removed from tank. It consists essentially of a primary and secondary coil, operating motor, and voltage relay mechanism. The regulator and mechanism is suspended in a cast iron tank, the lower part, containing the regulator core and coils, being filled with oil. The leads for the regulator are brought out at the upper part of the tank. The outgoing leads are compressed into bushings and connected to the leads of the regulator by means of terminals, the arrangements being such that the regulator with mechanism can be removed from the tank without difficulty. Besides the cover, the tank is also provided with a hinged door on the front side so as to give access to the mechanism. The door is provided with a gasket and the construction is practically rain and dust proof. However as there is always danger of the door not being clamped down perfectly, thus making it possible for water to enter the tank, a pocket has been provided inside the tank and underneath the door to collect the water. Capacity up to 2.3 kw., to control 2,300 volts, 60 cycle, 10 ampere feeders, and for a voltage range of 10 per cent. above or below normal, the operating motor and relay being designed for 110 or 220 volts. No provision is made for line drop compensation, although this can be obtained by installing a current transformer and a line drop compensator externally to the regulator.
It will be seen that the circuit comprising the dial, the secondary of the shunt, transformer and the secondary of the series transformer form a circuit which is not electrically connected to the main circuit. It can therefore be grounded without disturbing the main circuit as a safeguard to render it impossible for the pressure of the dial to be higher above the ground than the secondary voltage of the shunt transformer.