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Delco Generator No. 69 Geber

Buick Models D-54-55

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Fig. 303C.-Curves Showing Output of Delco Generator Number 68 at Various Engine Speeds.

This is exposed when the rear end cover is removed. This should receive oil once a week. No. 4-The oil hole in the distributor, at A, for lubricating the top bearing of the distributor shaft. This should receive oil once a week. No. 5-This is the inside of the distributor head. This should be lubricated with a small amount of vaseline, carefully applied two or three times during the first 2,000 miles running of the car, after which it will require no attention. This is to secure a burnished track for the rotor brush on the distributor head. This grease should be sparingly applied and the head wiped clean from dust and dirt.

Method of Current Output Regulation.-The voltage regulator which has been previously described and which was used on the 1914 and 1915 Delco Systems has been replaced by a system of "third brush excitation" in the 1916 systems. This has been very concisely described by the Delco engineers, and in order to make for accurate presentation of fact, the following descriptive matter is given in the same way as it appears in the Delco instruction books. There is really only one point in regard to the generating of electrical energy which is difficult to understand, and the best of scientists are at as much of a loss on this point as the average electrician. This one point can be expressed in the one sentence which is as follows: "Whenever the strength of the magnetic field or the amount of magnetism within a coil is changed an electro-motive force is induced or generated." This is variously expressed, but can be resolved into the same sentence as originally given. One of the most common expressions is, "Whenever an electrical conductor cuts the magnetic field or cuts magnetic lines of force an electromotive force is induced." In order to measure this electro-motive force, it is necessary to make connection from each end of the conductor to a suitable meter, by doing this a coil would be formed. Therefore, this expression means nothing different from the original expression. On account of being more readily understood, this expression will be referred to in connection with the explanation of the action of the generator.

The amount of the voltage that is induced (or generated) in any conductor or coil varies directly with the rate of the cutting of the magnetic lines; e.g., if we have a generator in which the magnetic

field remains constant and the generator produces 7 volts at 400 R. P. M., the voltage at 800 R. P. M. would be 14 volts, and it is on account of the variable speed of generators for automobile purposes that they must be equipped with some means of regulation for holding the voltage very nearly constant. The regulation of this generator is by what is known as third brush excitation, the theory of which is as follows:

The motor generator consists essentially of an iron frame and a field coil with two windings for magnetizing this frame. The armature, which is the revolving element, has wound in slots on its iron core a motor winding and a generator winding connected to corresponding commutators. Each commutator has a corresponding set of brushes which are for the purpose of collecting current from, or delivering current to the armature windings while the armature is revolving.

When cranking, current from the storage battery flows through the motor winding magnetizing the armature core. This acting upon the magnetism of the frame causes the turning effort. When generating the voltage is induced in the generator winding and when the circuit is completed to the storage battery this causes the charging current to flow into the battery. The brushes are located on the commutator in such a position that they collect the current while it is being generated in one direction. (The current flows one direction in a given coil while it is passing under one pole piece and in the other direction when passing under the opposite pole piece.) When the ignition button on the combination switch is first pulled out the current flows from the storage battery through the generator armature winding, also through the shunt field winding. This causes the motoring of the generator. After the engine is started and is running on its own power this current still has a tendency to flow in this direction, but is opposed by the voltage generated. At very low speeds a slight discharge is obtained. At approximately 7 miles per hour the generated voltage exceeds that of the battery and charging commences. As the speed increases above this point the charging rate increases as shown by the curve (Fig. 303C). The regulation of this generator is effected by what is known as third brush excitation.

SMUNT FIELD WINDING WHICH
PRODUCES THE MAGNETIC FIELD

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Since the magnetic field of the generator is produced by the current in the shunt field winding it is evident that should the shunt field current decrease as the speed of the engine increases the regulation would be affected. 1. order to fully understand this explanation it must be borne in mind that a current of electricity always has a magnetic effect whether this is desirable or not. Referring to Fig. 303D, the theory of this regulation is as follows: The full voltage of the generator is obtained from the large brushes marked "C" and "D." When the magnetic field from the pole pieces N and S is not disturbed by any other influence each coil is generating uniformly as it passes under the pole pieces. The voltage from one commutator bar to the next one is practically uniform around the commutator. Therefore, the voltage from brush C to brush E is about 5 volts when the total

S

+

D

Fig. 303D.-Diagram Illustrating Function of Third Brush In Regulating Delco Generator Output.

voltage from brush C to brush D is 61⁄2 volts and 5 volts is applied to the shunt field winding. This 5 volts is sufficient to cause approximately 14 amperes to flow in the shunt field winding.

As the speed of the generator is increased the voltage increases, causing the current to be charged to the storage battery. This charging current flows through the armature winding, producing a magnetic effect in the direction of the arrow B. This magnetic effect acts upon the main magnetic field which is in the direction of the arrow A with the result that the magnetic field is twisted out of its original position in very much the same manner as two streams of water coming together are each deflected from their original directions. This deflection causes the magnetic field to be

strong at the pole tips, marked G and F, and weak at the opposite pole tips with the result that the coils generate a very low voltage while passing from the brush C to the brush E (the coils at this time are under the pole tips having a weak field) and generates a greater part of their voltage while passing from the brush E to D. The amount of this variation depends upon the speed that the generator is driven; with the result that the shunt field current decreases as the speed increases as shown in the curve.

By this form of regulation it is possible to get a high charging rate between the speeds of 12 and 25 miles per hour, and it is with drivers whose average driving speed comes between these limits that more trouble is experienced in keeping the battery charged. At the higher speeds the charging current is decreased. The driver who drives his car at the higher speeds requires less current, as experience has taught that this type of driver makes fewer stops in proportion to the amount the car is driven than the slower driver. The output of these generators can be increased or decreased by changing the position of the regulating brush. Each time the position of the brush is changed it is necessary to sandpaper the brush so that it fits the commutator. Otherwise the charging rate will be very low due to the poor contact of the brush. This should not be attempted by any one except competent mechanics, and this charging current should be carefully checked and in no case should the maximum current on this generator exceed 22 amperes. Also careful watch should be kept on any machine on which the charging rate has been increased to see that the commutator is not being overloaded. Considerable variation in the output of different generators will be obtained from the curve shown, as the output of the generator is affected by temperature and battery conditions.

Condenser. The condenser consists of two long strips of folded tinfoil insulated from each other by paraffined or oiled paper, and connected as shown in Fig. 303 E. The condenser has the property of being able to hold a certain quantity of electrical energy, and like the storage battery, will discharge this energy if there is any circuit between its terminal. As the distributor contacts open the magnetism commences to die out of the iron core, this induces a voltage in both the primary and secondary windings of the coil.

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