Fig. 2,449.—General Electric pole type regulator in service; its construction is shown in fig. 2,450.
The majority of the consumers may, however, obtain sufficiently good voltage while a few may have reason for criticism. To overcome this difficulty it is necessary either to increase the copper in the feeder or else to install small automatic regulators.
There are also cases where a small amount of power is transmitted a long distance through a feeder direct from the station.
The amount of copper required to reduce the line drop is usually too great to be considered and the cost of the ordinary automatic regulator is also comparatively high. In such cases small pole type regulators as shown in fig. 2,449 are desirable.
Ques. Describe the operation of the regulator mechanism shown in fig. 2,450.
Ans. Assuming the voltage to be normal, the balance arm of the relay will be held horizontal, the trips F will not engage with the triggers E, and no movement is therefore transmitted to the ratchet wheel C. If the voltage drops below normal, the left hand trip will descend until it finally gets in the way of the left hand trigger just before it reaches the limit of its counterclockwise travel. This trigger will therefore release the left pawl D, which will engage with the ratchet wheel and will consequently turn it clockwise until the rocker arm reaches its right hand limit. Before the rocker arm reaches the left hand limit, the released pawl must be locked by its trigger, so that if the voltage has reached its normal value, further movement of the ratchet wheel will not take place, whereas if the voltage be still too low, the trigger will again release the pawl by striking the trip of the relay.
Fig. 2,450.—Mechanism of General Electric pole type regulator. The operating motor (described in fig. 2,438) is direct connected to a worm and gear, the shaft of which is provided with a bell crank. A rod A, connects the crank with the rocker arm B, which thus may be caused to oscillate over a ratchet wheel C. The rocker arm is provided with two pawls D, which can engage with the teeth of the ratchet wheel, so that this wheel can be rotated one way or the other. The ratchet wheel is mounted on the same shaft as a worm, which engages with the gear segment carried by the regulator shaft, so that the movement of the ratchet wheel is directly transmitted to the regulator. Besides the two large pawls D, the rocker arm also carries two smaller ones E, called the triggers. These triggers usually hold the pawls locked in such positions as not to engage with the ratchet wheel, but the pawls will be released when the triggers strike the trips F of the relay arm. A limiting device for the movement of the ratchet wheel and the regulator segment is provided, as shown. This device consists of two cams K, mounted on a common arm, which can turn on the shaft of the ratchet wheel. Normally these cams are not within reach of the pawls, but through a lever arrangement, controlled by the regulator segment, the arm holding the cams may be rotated so that, if the trigger has been raised, so as to release the pawl, the tip of the pawl will bear on the cam of the limiting device, and before the pawl can engage with the ratchet wheel it has already been locked by its trigger. A further movement of the ratchet wheel in that particular direction is therefore impossible, while it is free to be moved the other way. A positive stop for the gear segment is also provided. The motor is provided with oil ring bearings, and the gear for the motor worm runs in oil, the supporting casting forming a well therefor.