AC-DC GENERATING SYSTEM

• US 3,829,758 A
• Filed: 02/02/1972
• Issued: 08/13/1974
• Est. Priority Date: 02/02/1972
• Status: Expired due to Term

• Current Assignee: BorgWarner Incorporated
• Original Assignee: George H. Studtmann
• Inventors: Studtmann, George H.
• Primary Examiner(s): Shoop, Jr., William M.
• Application Number:
  US05/222,939
• Time in Patent Office: 923 Days
• Field of Search: 322/20,27,47,94,28 321/5,45C
• US Class Current: 322/28
• CPC Class Codes: H02K 17/42 Asynchronous induction generators H02K17/02 takes precedence
• CPC Class Codes: H05K 7/18 Construction of rack or frame

Abstract

An induction machine driven as a generator has its output connections coupled to the output connections of a static inverter circuit, connected to operate not as an inverter but as a switching system. A capacitor is coupled to the bus conductors of the switching system. D-c excitation is furnished to the induction generator system only for starting, and is then disconnected. At rated speed the static inverter circuit operates as a switching system to regulate connection of the capacitor to the induction generator on a time-sharing basis, replacing the directly connected capacitor bank in known systems. In multiphase systems the capacitor is not required, as the switching system periodically directs the flow of reactive energy from one phase to another of the inductive machine. By regulating the frequency of the switching operation the overall system can be made to generate effectively over a wide range of input speeds. An a-c output voltage is available from the common terminals between the induction generator and the switching system, and a d-c output voltage is also available from separate conductors of the switching system.

Claims

1. A power transfer system for providing a-c and/or d-c voltages, comprising:

an induction machine having a mechanical input shaft, a plurality of output conductors for supplying an a-c output voltage, and means for enabling the induction machine to build up during start-up;

a capacitor;

a switching system, including a plurality of output connections coupled to the induction machine output conductors, and a plurality of additional connections coupled to said capacitor, said system including a plurality of switches connected to receive actuating signals to control the switching frequency; and

means, including an oscillator-and-logic circuit, connected to regulate the actuating times of the switches in the switching system, to thus regulate the frequency or the amplitude of output a-c energy provided by the power transfer system.

2. A power transfer system as claimed in claim 1, in which the oscillator in the oscillator-and-logic circuit is connected to operate at a fixed frequency, thus maintaining a fixed frequency output a-c energy from the power transfer system.

3. A power transfer system as claimed in claim 1, in which the oscillator in the oscillator-and-logic circuit is connected to operate at a variable frequency as a functiOn of variations in the speed of the mechanical input shaft of the induction machine, thus maintaining a constant amplitude of the output a-c energy from the power transfer system.

4. A generating system for providing a-c and/or d-c voltages, comprising:

an induction machine having a mechanical input shaft, a plurality of output conductors for supplying an a-c output voltage, and means for enabling the induction machine to build up during start-up;

a capacitor;

a switching system, including a plurality of output connections coupled to the induction machine output conductors, a pair of additional connections coupled to said capacitor, from which additional connections a d-c output voltage can be supplied, and a plurality of semiconductor switches connected to receive gating signals to control the frequency of circuit switching; and

means, including an oscillator-and-logic circuit, connected to regulate the turn-on times of the semiconductor switches in the switching system to thus regulate the frequency or the amplitude of output a-c energy provided by the generating system.

5. The method of generating a-c and/or d-c voltages, comprising the steps of:

providing an induction machine having a mechanical input shaft and a plurality of output conductors;

providing a capacitor;

providing a switching system, coupling the switching system output connections to the induction machine output conductors, and coupling a pair of additional connections in the switching system to the capacitor;

rotating the induction machine input shaft while supplying an excitation voltage approximately an order of magnitude less than the normal operating voltage level of the induction machine; and

at approximately rated speed, removing the startup excitation voltage so that no external electrical energy is supplied to the system, while regulating the turn-on times of the semiconductor switches in the switching system to regulate the effective capacity coupled to the induction machine output conductors, thus regulating the amplitude or frequency of the output voltage supplied by the system.

6. A generating system for providing a-c and/or d-c voltages, comprising:

an induction generator, having a mechanical input shaft, a plurality of output conductors for supplying an a-c output voltage, and means for applying an excitation voltage, of a level approximately an order of magnitude less than the normal rated voltage level of the induction generator, to the induction generator only during start-up;

a capacitor;

a switching system, including a pair of bus conductors coupled to the capacitor, a plurality of output connections individually coupled to the respective induction generator output conductors, and a plurality of controlled rectifiers individually connected to receive gating signals for controlling the rectifier conduction times;

means, including an oscillator-and-logic circuit, connected to regulate the application of the gating signals to the controlled rectifiers to regulate the amplitude or frequency of the system output voltage; and

means for rotating the input shaft of the induction generator.

7. A generating system as claimed in claim 6 and further comprising a voltage comparator stage, having input connections coupled both to the induction generator output conductors and to a reference voltage unit, connected to regulate operation of the oscillator-and-logic circuit to govern the timing of the gating signals in the proper sense to maintain constant the amplitude of the system output voltage.

8. A bi-directional power transfer system for transferring power in a first direction during start-up of a mechanical unit having a drive shaft and thereafter reversing the direction of power transfer from the mechanical unit to an electrical load, comprising:

a switching system, having a pair of bus conductors, a plurality of output connections, and a plurality of semiconductor switches connected to receive gating signaLs for regulating turn-on of the semiconductor switches;

a capacitor coupled to the bus conductors;

an induction machine, having a mechanical shaft and a plurality of output conductors coupled to the plurality of switching system output connections;

means for coupling the drive shaft of the mechanical unit to the mechanical shaft of the induction machine;

means, including a first switch, for transferring d-c energy to the switching system bus conductors during system start-up, to provide an a-c output voltage from the switching system which energizes the induction machine as a motor and transfers mechanical drive to the mechanical unit to drive it up to rated speed; and

means, including a second switch, for completing an electrical circuit to transfer d-c energy from the switching system bus conductors to the electrical load as the induction machine is driven by the mechanical unit to operate as a generator which passes energy through the switching system to supply the electrical load.

9. A power transfer system as claimed in claim 8, and further comprising:

an oscillator-and-logic circuit connected to provide the gating signals for the semiconductor switches in the switching system;

a comparator stage, having a first input connection connected to receive a signal which varies as a function of the amplitude of the voltage at the induction machine output connections, a second input connection connected to receive a reference signal, and an output connection for supplying a control signal which varies as a function of amplitude variations of the induction machine output a-c voltage; and

means for coupling the comparator output connection to the oscillator-and-logic circuit, to regulate the frequency of the gating signals and thus maintain constant the amplitude of the voltage at the induction machine output connections.

10. A power transfer system as claimed in claim 8, and further comprising:

an oscillator-and-logic circuit connected to provide the gating signals for the semiconductor switches in the switching system;

a comparator stage, having a first input connection connected to receive a signal which varies as a function of the amplitude of the switching system bus current, a second input connection connected to receive a reference signal, and an output connection for supplying a control signal which varies as a function of amplitude variations of the switching system bus current; and

means for coupling the comparator output connection to the oscillator-and-logic circuit, to regulate the frequency of the gating signals as a function of the switching system bus current.

11. A power transfer system for providing a-c and/or d-c voltages, comprising:

an induction machine having a mechanical input shaft, a plurality of output conductors for supplying a multi-phase a-c output voltage, and means for enabling the induction machine to build up during start-up;

a switching system, including a plurality of output connections coupled to the induction machine output conductors, said system including a plurality of semiconductor switches connected to receive gating signals to control the switching frequency and periodically direct the flow of reactive energy from one phase circuit of the induction machine to another phase circuit of the machine; and

means, including an oscillator-and-logic circuit, connected to regulate the turn-on times of the semiconductor switches in the switching system, to thus regulate the frequency or the amplitude of output a-c energy provided by the power transfer system.