1942 - 1947 Chevrolet Shop Manual



	12-7

	To thoroughly understand the function of the voltage regulator, some knowledge of the characteristics of a storage battery is necessary. Figure 11 shows a series of curves, each depicting the charge indicated by the specific gravity of the acid, as the charging current is increased or decreased. The voltage increases with the charging rate and is highest for a fully charged (1.280) battery.	that 3 amperes. This method of charging is known as the "Constant Potential System," and is considered to be the ideal way of charging a battery, since it permits a high rate charge for a discharged battery, but tapers off the charging rate as the battery comes up, thereby preventing excessive overcharge. CURRENT AND VOLTAGE REGULATOR CONSTRUCTION In discussing the construction of the combination current and voltage regulator, the voltage regulator must be covered first, then the current regulator. VOLTAGE REGULATOR The voltage regulator unit consists of an iron core, which with its windings forms an electro magnet. The voltage winding consists of a large number of turns of fine wire. One end of this winding is connected to the generator (GEN) terminal of the regulator and the other end of the winding is grounded. This winding is known as a voltage coil because it is connected directly across the generator armature at all times and is subjected to the generator voltage, Fig. 12.


	Fig. 11-Battery Charging Curve Assume that the voltage regulator is set to open the contacts when the battery voltage reaches 7.5 volts. With the contacts open, the generator field circuit must go to ground, through the resistance which decreases the field current, the generator output and, consequently, the battery terminal voltage. This decrease in battery voltage allows the contacts to close again, and the repetition of this cycle many times each second holds the battery voltage at 7.5 volts. To be a little more accurate, it holds the current into the battery to a value which produces 7.5 volts at the battery terminals as shown on the curves of Fig. 11. Suppose the battery is nearly discharged, and has a specific gravity of 1.190. By following the curve marked 1.190 until it intersects the line of 7.5 volts, the current necessary to produce 7.5 volts will be found to be 18.4 amperes. The regulator will hold the current at this value until the battery starts to come up. When the specific gravity has reached 1.220, the current will have been reduced to 16.8 amperes; at 1.250 it will be 14.6 amperes; at 1.255, 10.6 amperes, and so on until at 1.280 the current will have dropped to less
		Fig. 12-Voltage Regulator Voltage Coil The series winding on the core consists of a few turns of larger diameter wire, one end of which is connected to the field (F) terminal of the regulator and the other end to the upper point mounting of the current regulator, Fig. 13. This winding

		Fig. 13-Voltage Regulator Series Coil is known as a series coil because it is connected in series with the shunt field of the generator.