Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . ed to the armature, it will be butlittle. If the armature (as in some arc dynamos) isvery strong compared to the field, it will be consider-able. In dynamos, with increasing load, the brushes shouldbe shifted in the direction of rotation and in the oppo-site direction when the load decreases. Never allow a dynamo or motor to stand in a dampplace uncovered. Moisture is apt to soak into thewindings and cause a short circuit or ground whenstarted. Great care should also be used should it everbe found
Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . ed to the armature, it will be butlittle. If the armature (as in some arc dynamos) isvery strong compared to the field, it will be consider-able. In dynamos, with increasing load, the brushes shouldbe shifted in the direction of rotation and in the oppo-site direction when the load decreases. Never allow a dynamo or motor to stand in a dampplace uncovered. Moisture is apt to soak into thewindings and cause a short circuit or ground whenstarted. Great care should also be used should it everbe found necessary to use water on a heated the water is allowed to reach the armature or com-mutator, it is bound to cause trouble. Water shouldonly be used in case of emergency, and then sparingly* CHAPTER IVOPERATION OF DYNAMOS Constant Potential Dynamos. In order to thoroughlyexplain the operation of dynamos, let us assume thatwe have the task of starting a new shunt dynamo, onethat has never generated any current. Our first step isto open the main switch and turn the rheostat or field. FIGURE 37. resistance box so that all the resistance is in rheostat consists of a number of resistances, Fig. 37,so arranged that they can be cut in or out of the circuitwithout opening the circuit. By reference to the figureit will be seen that the current enters at the handle andfrom there passes to the contact point upon which the65 ()() ELECTRICITY FOR ENGINEERS handie happens to rest. If the handle is at i the cur-rent must pass through all the wire in the box; if it isat 2 it simply passes through the handle and out. Rheostats for the shunt circuit of a dynamo shouldhave sufficient resistance, so that when it is all insertedthe voltage of the dynamo will slowly sink to method of stopping the action of a dynamo is
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