From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Journal article detailing the design, function, and adjustment of a 12-volt automotive voltage regulator.
| Identifier | ExFiles\Box 31\1\ Scan174 | |
| Date | 1st June 1925 | |
| Vol. XVI June, 1925 No. 6 576 THE JOURNAL OF THE SOCIETY OF AUTOMOTIVE ENGINEERS it has been advantageous to use the latter scheme. Both have proved satisfactory in service. Voltage regulation is effected by cutting resistance into the field circuit, thus weakening the field current to lower the voltage of the generator; and by cutting-out this resistance to cause the voltage to rise. If this resistance is cut in and out rapidly, an average condition of field strength will be maintained; that is, the field current will not have time to fall to the point corresponding to all the resistance in, nor will it have time to rise to the point it would normally reach with all the regulating resistance out. This is due to the rapidity of contact action and to the inductance of the circuit. Instead of reaching the maximum and falling again to the minimum as contact is made and broken the field current is suspended somewhere between these two extremes, the result being an intermediate value of field current and of terminal voltage. If the contacts have a high frequency, the flicker of the lamp will be imperceptible; if the beat is slow and distinct, flicker will result. The regulator must be designed so that it will respond to changes in the circuit; that is, it must function to raise the terminal voltage slightly under some conditions and to lower it under others. FIG. 3—THE VOLTAGE REGULATOR This Device Is Designed To Furnish Regulated-Voltage Energy to Battery and Lighting Circuits on Motor Vehicles, To Maintain the Voltage within Limits Required for Sufficient Steady and Non-Flickering Light from Connected Lamps, To Assure Long Lamp-Life by Preventing Excessive Voltage and To Provide the Tapering Charging Rate, Beneficial to the Battery, Which Results Automatically from Regulated-Voltage Charging. Its Main Elements Are a Reverse-Current Relay or Circuit-Breaker and the Regulating Device, Which Comprises a Specially Constructed Magnet and a Pivoted Armature That Opens and Closes a Pair of So-Called Regulating Contacts In the regulator described later, an extremely high armature-beat is attained, and it is responsive to changes of load and of speed within the working range of any given system. The contacts handle the insetting and cutting-out of regulating resistance in an almost spark-less manner, so that they have long life and require little attention. A very strong spring-tension is used that results in a self-cleaning action on the contacts as well as making the instrument free from interruptions due to vehicle vibration. Metallic points are used; hence, no danger of changing adjustment due to contact wear exists as is the case with carbon and similar materials when used for contact points. The field circuit is never broken entirely; the regulating resistance is simply shunted. A unique arrangement of connections provides the desired regulating characteristics and flexibility of application and adjustment. THE REGULATOR The 12-volt voltage-regulator is designed to furnish regulated-voltage energy to battery and lighting circuits on motor vehicles, to maintain the voltage within the limits required for sufficient, steady and non-flickering light from connected lamps, to assure long lamp-life by preventing excessive voltage and to provide the tapering charging rate, beneficial to the battery, which results automatically from regulated-voltage charging. Two distinct elements are contained in the control box: First, as shown in Fig. 3, the reverse-current relay or circuit-breaker A which, in varied design, is in common use on almost all automotive electrical systems. This relay prevents the discharge of the battery through the generator circuit when the generator is not operating. It consists of a magnet, B, which operates an armature to open and close a pair of contact points, C. Second, the regulator element D, which comprises a specially constructed magnet, E, and a pivoted armature, F, which opens and closes a pair of contacts, G, called the regulating contacts. When the system is functioning properly, the following characteristics will be noted: (1) Very little or no variation in the intensity of light from connected lamps on sudden changes of load or engine speed will be noticed (2) A voltmeter, if connected across the load, will show a steady reading (3) Little or no sparking between the contact points of the regulator will occur (4) The rate of vibration of the regulator armature will be steady and high. It will not "flutter" slowly back and forth, or stick in one position (5) The variation of voltage with the load disconnected, that is, with no lights or battery in the circuit but with the regulator connected to the generator, will be very slight when the speed of the generator is raised or lowered rapidly, within the working range, above the point where the circuit-breaker contacts close and the regulator begins to operate In the interior view of the voltage regulator, Fig. 3, two sets of terminal posts extending through the control box are shown. The two terminals H and I connect with the load; that is, with the battery and the lights. The other set J, K and L connect with a similar set of terminals on the generator by a three-conductor cable, provided with one triple-contact connecting-plug at each end. One of these three terminal posts L is smaller than the other two so that the cable plugs cannot be attached incorrectly. The cable terminals are locked in place securely by a metal protecting-sleeve that is threaded to fit similar threads on the terminal-post base, at the generator and at the control box, thus assuring a tight connection at all times. The regulator operation is not affected by any change in temperature that may occur under the hood of a motor vehicle in normal operation. CIRCUIT-BREAKER AND REGULATOR ADJUSTMENTS Spring tension on the spring M, produced by the screw and the locking nut N, provides an adjustment on the circuit-breaker. Relieving the spring tension will cause the contact points to close at a lower voltage and to open at a higher current value. The circuit-breaker setting is important on high-capacity generators, and should conform to the average service requirements as closely as possible. If the circuit-breaker closes at too low a voltage, a period of battery discharge will result, as it may be possible that the battery voltage is higher than the generator voltage at low speeds. If the circuit-breaker closes at too high a voltage, initially, a period of waste driving time will ensue during which the battery will not be charged, although the generator voltage is sufficient to drive through a charging current. | ||