Abstract:
Two alternators of a motor vehicle are operated in parallel from current supplied from a battery by way of two transistors respectively. A regulator senses the voltage output of the battery to control the two transistors.

Description:
SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a system wherein two alternators of a motor vehicle are operated from the current supplied to their rotors from a battery by way of two transistors respectively. A regulator senses the voltage output of the battery to control the two transistors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG.1 is an electrical schematic of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is illustrated two rotor coils 21 and 23 of two alternators respectively of an emergency vehicle. The alternators are employed for charging a twelve volt battery 25 of the vehicle and for supplying power to a load (not shown) as described in connection with FIG. 2 of U.S. Pat. No. 4,336,485. This patent is hereby incorporated by reference into the present application. The emergency vehicle may be for example, an ambulance. The battery 25 supplies power to the vehicle chassis electrical system by way of lead 26. The plus terminal of battery 25 is connected to the rotors 21 and 23 by way of two identical power transistors 27 and 29 respectively. Electrical lead 31 connects the plus terminal of battery 25 to the collector 33 of transistor 27 and electrical lead 33 connects the emitter 35 of transistor 27 to rotor 21. Electrical lead 37 connects the plus terminal 25 of the battery 25 to the collector 39 of transistor 29 and electrical lead 41 connects the emitter 43 of transistor 29 to the rotor 23. The diodes 45 and 47 are provided to eliminate the reactance from the rotor 21 and 23 respectively. 
     A regulator 51 is provided having its F terminal connected to the base 53 of transistor 27 by way of electrical leads 55 and 57 and to the base 59 of transistor 29 by way of electrical leads 55 and 61. The B terminal of regulator 51 is connected to the plus terminal of the battery 25 by way of leads 63 and 37. A start switch 65 is provided in lead 67 which is coupled from the S terminal of regulator 51 to lead 37 and hence to the plus terminal of the battery 25. The regulator 51 may be set for example to regulate the output of the battery 25 such that it does not exceed 14.5 volts. 
     In operation, the switch 65 is closed. Current to the bases 53 and 59 of transistors 27 and 29 from the F terminal of regulator 51 causes the transistors to conduct whereby current flows to the rotors 21 and 23 from the battery 25 by way of the transistors 27 and 29. If the voltage on the B terminal of the regulator 51 reaches 14.5 volts, the voltage on the F terminal of regulator 51 drops whereby transistors 27 and 29 become less conductive and less current from the battery 25 flow to the rotors 21 and 23. This reduces the charging current to the battery 25. 
     In the system of FIG. 1 a single regulator is employed for regulating two alternators connected together in parallel. The use of the two transistors 27 and 29 has advantages since they provide the same amount of current from the battery to the two rotors of the alternators. The same amount of output current and voltage also are obtained from the two alternators for charging purposes and for supplying power to the load. The two alternators thus are balanced whereby one alternator does not become predominate which is undesirable since the predominate alternator will wear out before the other alternator. Since current to the two rotors from the battery flows by way of the two transistors 27 and 29 rather than from the regulator 51, high current requirements by the two alternators will not burn out the regulator 51. In one embodiment, each of the transistor is rated at 30 amps. They protect the regulator 51 in that only about 40 mils of current is drawn by the regulator output to control the two transistors. If one transistor fails, the other transistor and alternator provide a back up for charging the battery and for providing power to the load.