SELF-EXCITATION DEVICE FOR AN ALTERNATOR

• US 3,745,441 A
• Filed: 06/19/1972
• Issued: 07/10/1973
• Est. Priority Date: 06/19/1972
• Status: Expired due to Term

• Current Assignee: Gilbert Vidal, Jacques Soffer
• Original Assignee: Gilbert Vidal, Jacques Soffer
• Inventors: Soffer, Jacques, Vidal, Gilbert
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Huberfeld, H.
• Application Number:
  US05/264,325
• Time in Patent Office: 386 Days
• Field of Search: 322/14,15,16,20,24,25,28,70,73,75,76,78 290/11,14 318/142,158
• US Class Current: 322/20
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 50/12 using AC generators and DC motors
• CPC Class Codes: H02P 9/30 using semiconductor devices
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Abstract

Self-excitation device for an electric supply alternator supplying, through a rectifier bridge, direct current motors, more particularly, drive motors for self-propelled railway vehicles fitted with heat engines and electric transmission. In order to increase the control precision, each thyristor of the bridge supplying the excitation winding of the alternator is controlled by a control circuit which is synchronized with the help of a selection circuit, by one or the other of the voltages obtained between the outputs of the alternator and ground.

Claims

1. A self-excitation control device for controlling the energization of an excitation winding of an alternator for supplying direct current motors from multi-phase output terminals through a rectifier supply bridge, said control device comprising an excitation bridge including a thyristor connected between each respective phase output of said alternator and a common point connected to one side of said excitation winding and a rectifier connected between each respective phase output of said alternator and the other side of said excitation winding;

a diode connected in parallel with said excitation winding;

comparator means for comparing the voltage rectified by said rectifier supply bridge with a reference voltage so as to provide a difference signal representing the difference between these two voltages;

a plurality of gate control circuits each having an output connected to the control electrode of one of said thyristors, one regulation input receiving said difference signal, two phase inputs and one control input;

means for applying to each of said phase inputs of said gate control circuits a reference phase signal representative of the voltage between a respective one of the output terminals of said alternator and said other side of said excitation winding;

selection means responsive to the operation of said motor and alternator for applying to said control input of said gate control circuits a logic signal of first or second value, so that each gate control circuit provides an ignition signal to a thyristor after one of said two phase inputs thereof has received a reference phase signal with a time shift controlled by said difference signal, the phase input receiving said reference phase signal being determined by the value of said logic control signal.

2. A device according to claim 1 wherein an amplitude limiting circuit is connected in parallel with said excitation winding to protect said winding against excess voltages, said amplitude limiting circuit comprising a transformer having a primary and a secondary winding, said primary winding being connected in series with a capacitor across said excitation winding and said secondary winding being connected through a rectifier across a battery.

3. A device according to claim 1 wherein said comparator means includes an amplifier having a controllable amplification factor for amplifying said difference signal and means for inversely varying said amplification factor of said amplifier in accordance with the level of voltage rectified by said supply bridge.

4. A device according to claim 1 wherein each of said gate control circuits comprises a control capacitor, a first switch, charge means connected in series with said first switch between said regulation input and said control capacitor so as to charge said control capacitor in dependence on the value of said difference signal when said first switch is closed, a second switch, first discharge means connected in series with said second switch to said control capacitor to sample the discharge current of said capacitor when said second switch is closed, a third switch, second discharge means connected in series with said third switch to said control capacitor to sample the discharge current of said capacitor when said third switch is closed, detector means for producing a discharge control signal when the charge of said control capacitor has reached a predetermined value, and logic circuit means for controlling the operation of said first, second and third switches in response to signals on said control input and said phase inputs along with said discharge control signal.

5. A device according to claim 4 wherein one phase input of each gate control circuit is connected to a low pass filter which filters the reference phase signal applied thereto.

6. A device according to claim 1 wherein said selection means includes a bistable circuit controlled by said difference signal so that said logic signal passes fRom said first to said second value when said time shift exceeds a first predetermined threshold and from said second to said first value when said time shift becomes lower than a second predetermined threshold which is lower than said first threshold.

7. A device according to claim 6 wherein an amplitude limiting circuit is connected in parallel with said excitation winding to protect said winding against excess voltages, said amplitude limiting circuit comprising a transformer having a primary and a secondary winding, said primary winding being connected in series with a capacitor across said excitation winding and said secondary winding being connected through a rectifier across a battery.

8. A device according to claim 7 wherein said comparator means includes an amplifier having a controllable amplification factor for amplifying said difference signal and means for inversely varying said amplification factor of said amplifier in accordance with the level of voltage rectified by said supply bridge.

9. Self-excitation device for an alternator connected through a rectifier bridge to at least one direct current motor and having an excitation winding, comprising excitation means for deriving a direct current voltage from the output of said alternator and connection means for applying said direct current voltage to said excitation winding, said excitation means including a thyristor connected between each respective phase output of said alternator and a common point, said connection means connecting said common point to said excitation winding, and control means responsive to the output of said alternator for sequentially triggering said thyristors, said control means including gate control means for generating gate control signals which are shifted in phase in relation to the anode voltage of said thyristors through an angle which is regulated in proportion with the difference between the alternating current output voltage of said alternator and a reference voltage so that said alternating current output voltage is maintained approximately equal to said reference voltage, wherein a resistive attenuator is connected between each phase output of said alternator and said gate control means, said gate control means including a comparator having one input connected to the output of said rectifier bridge and another input receiving said reference voltage, a gate control device having inputs connected to the outputs of said comparator and to each phase output of said alternator through said resistive attenuators, and triggering circuit means responsive to outputs from said gate control device for triggering said thyristors, said control means further including a transformer having a primary winding connected between the cathodes of said thyristors and ground through a high capacity condenser and a secondary winding connected in series with a diode across a non-inductive direct current source, said diode being poled in a direction wherein it blocks application of direct current to said secondary winding when non-conductive and said secondary winding being wound in a direction such that any positive voltage peak in the primary winding above a certain threshold has the effect of rendering the diode conductive.

10. Self-excitation device for an alternator as defined in claim 9 wherein an additional diode and said excitation winding are connected in parallel across the series combination of said primary winding and said high capacity condenser.