Continuous-Current Motors and Control Apparatus; A Practical Book for All Classes of Technical Readers (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 edition. Excerpt: ...contact 5, S2 will first suck up its core and contact plate, but will allow them to drop when the motor has speeded-up more and the current has decreased. The circuit of C3 will then be completed from contact 4 and K3 will be pulled on, thus short-circuiting R2. In the same manner, if4 next shorts Rs, and K5 afterwards shorts Rt through its contact 11. The pulling-on of K5 opens its two interlocks I5 and I6'; and the action of the latter is to break the circuit of C2 and so release K2. This will result in cutting current off from C3 and the opening of K3; and the same will then happen to C4 and The opening of the latter will not, however, de-energise C5, for when Kh went on, an alternative connection was provided through a high resistance Z. We have now reached the full running position of this control apparatus, with Ki and K5 closed and K2-K4 open, the whole of the resistance being cut out by the bar cb. To stop the motor, the button marked Stop is pressed. This de-energises coils C1 and C5, opens their contactors, and so cuts off all current from the motor. The push-buttons are generally mounted side by side, as in Fig. 101, but they are here shown apart to simplify the figure. An endeavour has been made to show the rubbing contacts with which they must be provided, though it is usually sufficient for diagram purposes to indicate them like testing keys, as in Fig. 90. 48. SEMI-AUTOMATIC CONTROLS.--Any control which is started into action by closing a small switch, or a master controller, or by pressing a button, may be described as semi-automatic. The apparatus diagrammed in Figs. 86, 89, 90, 91, and 94, for example, come under this class, and'others are described in following pages. The fact that the motor can be stopped in a similar...