Management of Dynamo-electric Machinery: Parts 1-2

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Page 13 - It has been found that the best results are obtained when the tension in the driving side of the rope is only 3 to 4 per cent of the breaking strength.
Page 11 - A regular belt lacing of strong pliable leather or a special wire is used. The lacing is doubled to find its middle; and the two ends are passed through the two holes marked " 1 " and " la," precisely as in lacing a shoe. The two ends are then passed successively through the two series of holes, in the order in which they are numbered, 2, 3, 4, etc., and 2a, 3a, 4a, etc., finishing at 13 and 13a, which are additional holes for securing the ends of the lace.
Page 46 - Fig. 32, but in this instance they magnetize the field in the same direction, or, in other words, their effect is cumulative. This type of motor possesses the powerful starting torque feature of the series motor, but a less variable speed with varying loads. It is employed where a great starting torque and a fairly uniform running speed are required, as, for example, with electric hoists or elevators.
Page 17 - The lower limit is specified for rubber-covered wires to prevent gradual deterioration of the high insulation by the heat of the wires, but not from fear of igniting the insulation. The question of drop is not taken into consideration in the above table.
Page 54 - ... to an accidental contact with some other wire or to a change of connections. Tools with insulated handles, or a dry stick of wood, should be used instead of the bare hand. The rule to use only one hand when handling dangerous electrical conductors or apparatus is a very good one, because it avoids the chance, which is very great, of making contacts with both hands and getting the full current right through the body. This rule is often made still more definite by saying, " Keep one hand in your...
Page 49 - The satisfactory use of alternating currents for power purposes depends mainly on the polyphase induction motor, as in this form the AC motor is self-starting with considerable torque and operates at a practically constant speed from no load to a heavy overload. Induction motors are designed for the standard voltages and frequencies. In most induction motors now built, the primary, or part into which the currents from the line are led, is the stationary member, or stator. The secondary, in which...
Page 18 - ... circuits except in an emergency. In practice, however, some form of electro-magnetic circuit-breaker is employed for the purpose, and may be operated automatically with overload, or by hand at any time. Knife switches should be so placed that gravity tends to open rather than to close them. They should always be located in dry. accessible places and grouped as far as possible If located in exposed positions they should be enclosed in slate or equivalently lined cabinets. The distances between...
Page 40 - Held coils are wound with wire of such a size as to have the proper resistance, and resulting magnetizing current; and since the potential applied is practically constant, the field strength is constant. In starting shunt motors, no trouble is likely to occur in connecting the field to the circuit. The difficulty is with the armature current, because the resistance of the armature is very low in order to get...
Page 13 - Driving possesses advantages over ordinary belting in some cases. The rope runs in V-shaped grooves in the peripheries of the pulleys, and thereby obtains a great grip by a sort of wedging action. The kinds of rope ordinarily employed for this purpose are cotton, hemp, rawhide and wire. The general advantages are: 1. Economy in cost. 2. Large amount of power that can be transmitted with a given diameter and width of pulley, on account of the grip obtained. 3. It is almost noiseless. 4. Ropes, on...
Page 27 - A self-exciting or compound- wound alternator requires the brushes that supply the direct current to the field to be reversed upon the Fig. 17. commutator, and their tips moved through an angle as above stated, if the rotation is to be reversed. In any case, copper brushes (unless they be gauze brushes pressing radially upon the commutator) should point in the direction of rotation; but carbon brushes, particularly if they are perpendicular to the surface of the commutator, allow the armature to...

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