CONTENTS. The Operation and Care of Small EIectricaI Machinery, by HENRY B. BIXLER - - - 3 Dynamo and Motor Troubles - - 9 Repairs to the Commutator, by NORMAN G . MEADE - 16 Repairs to the Armature Winding, by NORMAN G. MEADE - - - - 22 Repairs to Armature and FieId Coils, by NORMAN G MEADE - , - - - - 31 Winding of Direct-Current Armature - . - -, p , v - . - 39 Copmi ht. 1910. The Induetdal Press. Publishers of WCI INERY. 49-65 Lafryette Straet, New York City CHAPTER I. THE OPERATION AND CARE OF SULL ELECTRICAL MACHINERY As the majority of uscrs of small electrical machinery are not familiar with the best methods employed to keep the machines in good running order and repair, the author alms to present a few practical suggestions, to be of some help in the making of necessary repairs, locating troubles, and removing the causes. The dynamo or motor should be instaIled in a dry place, and under no circumstances should water be allowed to come in contact with the machine. Excessive dampness always causes trouble, and this point should be guarded against. The machine ahonld be well ventilated, and kept free from dust as much as possible. Before starting a new machine, see that the bearings are well filled with good oil, and that the shaft turns freely i n the bearings. The oil-rings should turn with the shaft, and not stick, as the lubrication of the bearings depends upon the rings working right. This is important and should be care fully matched. If the machine is belt driven, the belt should not be too tight, as this mill cause undue wear on the bearing and may cause heating also. Always provide solid foundations or supports for the machine to rest on. Keep the machine cool, dry and clean, and very little trouble will result in its operation in general. When a new machine is installed and wired up, the connections should be carefully checked over to see whether they correspond with the diagram of connections sent with the machine. If this is found to be correct, and the machine refuses to act properly, the cause of the trouble should at once be located and the diaculty removed before going further. Troubles In the Field Coils First we mill consider the troubles that may exist in the field coils. and horn to proceed to correct them. If, on running a machine for some time, the field coils all become hot, the voltage may be too high and should be reduced to normal. If only a part of the coils becomes hot, it will usually be found that a connection exists between the coils and the frame of the machine called ground, which when found should be InsuIated with mlca or paper. Sometimes it will be found that some of the coils are cold while the remainder are excessively hot, and the cause of this is a short circuit in the cold coils, which means that the current i s not passing through the cofls. Test out the coils separately with a magneto or battery, and when the defective coil is found, it should be repaired by reinsulating it. A partial short circuit will cause the coils to heat, and should be fncn mrt n l , a rch, 1910. 4 No. 34-DYNAhi AND MOTOR REPAIRS treated as rrtaZcd abwk. in R . compo wd-woundm achine, i. e., one hav ing a shunt and series windlng on the field coils, an over-load will cause an excessive current to flow through the series coils, causing the heat to rise above normal. The load should be reduced or a shunt should be connected as shown in Fig. 1. This wiIl cause the current to divide, part of it flowing through the shunt, thereby reducing the heating of the series coils...