Patent Publication Number: US-2023145101-A1

Title: Dual saturable reactor power supply

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to power supplies, and more particularly to power supplies such as used to provide conditioned power to aircraft from onboard generators. 
     2. Description of Related Art 
     Aircraft 28 V systems are typically sourced by a permanent magnet generator (PMG) and rectifier. One of the topologies that has been utilized in the past is a saturable reactor or magnetic amplifier to help maintain a constant voltage over the entire load and speed range. 
     Each PMG phase is connected to a diode. The output of each diode is fed into the reactor, which is controlled by a control winding. The output of the reactor is then filtered. The neutral of the PMG acts as the negative rail or return path for the circuit. The reactor topology is beneficial over current switching power supply topologies because it is more cost effective. Additionally, the reactor topology can withstand higher heat due to the reactor construction. One drawback that must be balanced with these benefits is that the topology only utilizes the positive half of the PMG output voltage. As a result, the PMG must be upsized to provide the necessary power. 
     The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for power supplies. This disclosure provides a solution for this need. 
     SUMMARY 
     A power supply system includes a first AC phase input configured to connect to a first phase of a generator, second AC phase input configured to connect to a second phase of a generator, and a third AC phase input configured to connect to a third phase of a generator. A first saturable reactor is electrically connected to the first AC phase input, to the second AC phase input, and to the third AC phase input. The first saturable reactor is electrically connected to a first DC output. A second saturable reactor is electrically connected in parallel with the first saturable reactor to the first AC phase input, to the second AC phase input, and to the third AC phase input. The second saturable reactor is electrically connected to a second DC output. A reactor controller can be operatively connected to the first saturable reactor and to the second saturable reactor to regulate DC output voltage to the first and second DC outputs. 
     A neutral line can be configured to connect to a PMG neutral point, wherein the neutral line connects to a node between the first DC input and the second DC output. A first capacitor can be connected between the first DC output and the neutral line. A second capacitor can be connected between the second DC output and the neutral line. A node connected to the first capacitor, the second capacitor, and the neutral line can be connected to ground so a negative DC voltage can be output from the second DC output, and a positive DC voltage can be output from the first DC output. The second DC output can be connected to ground, and the node connected to the first capacitor, the second capacitor, and the neutral line can be configured to output an intermediate positive DC voltage, wherein the first DC output is configured to output a higher positive DC voltage than the intermediate positive DC voltage. 
     The first saturable reactor can connect to the first DC output through a first inductor, and the second saturable reactor can connect to the second DC output through a second inductor. A first impedance can connect a node between the first saturable reactor and the first inductor to ground. A second impedance can connect a node between the second saturable reactor and the second inductor to ground. A first grounded diode can connect the node between the first saturable reactor and the first inductor to ground, and can be oriented to impede current flowing to ground through the first diode. A second grounded diode can connects the node between the second saturable reactor and the second inductor to ground, and can be oriented to impede current flowing to ground through the second diode. 
     The first AC phase input can connects to the first saturable reactor through a first diode oriented to inhibit current from the first saturable reactor into the first AC phase input. The second AC phase input can connect to the first saturable reactor through a second diode oriented to inhibit current from the first saturable reactor into the second AC phase input. The third AC phase input can connect to the first saturable reactor through a third diode oriented to inhibit current from the first saturable reactor into the third AC phase input. The first AC phase input can connect to the second saturable reactor through a fourth diode oriented to inhibit current from the first AC phase input into the second saturable reactor. The second AC phase input can connect to the second saturable reactor through a fifth diode oriented to inhibit current from the second AC phase input into the second saturable reactor. The third AC phase input can connect to the second saturable reactor through a sixth diode oriented to inhibit current from the third AC phase input into the second saturable reactor. 
     The first saturable reactor can include a respective first reactor inductor for each of the first, second, and third AC phase inputs, and the first saturable reactor can include a respective control winding operatively associated with each of the respective first reactor inductors for controlling DC output voltage to the first DC output. The second saturable reactor can include a respective second reactor inductor for each of the first, second, and third AC phase inputs, and the first saturable reactor can include a respective control winding operatively associated with each of the respective second reactor inductors for controlling DC output voltage to the second DC output. 
     A permanent magnet generator (PMG) can include a first phase connected to the first AC phase input, a second phase connected to the second AC phase input, and a third phase connected to the third AC phase input. The PMG can include a neutral point connected between the first phase, second phase, and third phase of the PMG. The neutral point can be connected as a floating point between the first and second DC outputs. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG.  1    is a schematic view of an embodiment of a system constructed in accordance with the present disclosure, showing the permanent magnet generator PMG and the two saturable reactors; and 
         FIG.  2    is a schematic view of the system of  FIG.  1    with a different configuration for the neutral point of the PMG. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of a system in accordance with the disclosure is shown in  FIG.  1    and is designated generally by reference character  100 . Other embodiments of systems in accordance with the disclosure, or aspects thereof, are provided in  FIG.  2   , as will be described. The systems and methods described herein can be used to provide direct current (DC) power from an alternating current (AC) generator, e.g. aboard an aircraft. 
     A permanent magnet generator (PMG)  102  includes a first phase  104  connected to the first AC phase input  106 , a second phase  108  connected to the second AC phase input  110 , and a third phase  112  connected to the third AC phase input  114 . The PMG  102  includes a neutral point  116  connected between the first phase  104 , second phase  108 , and third phase  112  of the PMG  102 . 
     The first AC phase input  104  connects to the first saturable reactor  118  through a first diode  120  oriented to inhibit current from the first saturable reactor  118  into the first AC phase input  106 . The second AC phase input  110  connects to the first saturable reactor  118  through a second diode  122  oriented to inhibit current from the first saturable reactor  118  into the second AC phase input  110 . The third AC phase input  114  connects to the first saturable reactor  118  through a third diode  124  oriented to inhibit current from the first saturable reactor  118  into the third AC phase input  114 . 
     The second saturable reactor  126  is electrically connected in parallel with the first saturable reactor  118  to the first AC phase input  106 , to the second AC phase input  110 , and to the third AC phase input  114 . The first AC phase input  106  connects to the second saturable reactor  126  through a fourth diode  128  oriented to inhibit current from the first AC phase input  106  into the second saturable reactor  126 . The second AC phase input  110  connects to the second saturable reactor  126  through a fifth diode  130  oriented to inhibit current from the second AC phase input  110  into the second saturable reactor  126 . The third AC phase input  114  connects to the second saturable reactor  126  through a sixth diode  132  oriented to inhibit current from the third AC phase input  114  into the second saturable reactor  126 . 
     The first saturable reactor  118  includes a respective first reactor inductor  134  for each of the first, second, and third AC phase inputs. The first saturable reactor  118  also includes a respective control winding  136  operatively associated with each of the respective first reactor inductors  134  for controlling DC output voltage to the first DC output  138 . The second saturable reactor  126  similarly includes respective second reactor inductors  134  and control windings  136  for controlling DC output voltage to the second DC output  140 . 
     A reactor controller  142  is operatively connected to the first saturable reactor  118  and to the second saturable reactor  126  to regulate DC output voltage to the first and second DC outputs  138 ,  140 . The reactor controller  142  controls saturation of the inductors  134  in the reactors  118  and  126  by controlling the control windings  136 . 
     The first saturable reactor  118  connects to the first DC output  138  through a first inductor  144 . The second saturable reactor  126  connects to the second DC output  140  through a second inductor  146 . A first impedance  148 , e.g. a resistor, connects a node  150  between the first saturable reactor  118  and the first inductor  144  to ground  152 . A second impedance  155 , e.g. a resistor, connects a node  156  between the second saturable reactor  126  and the second inductor  146  to ground  155 . A first grounded diode  158  connects the node  150  to ground  155 , and is oriented to impede current flowing to ground  155  through the first diode  158 . A second grounded diode  160  connects the node  156  to ground  155 , and is oriented to impede current flowing to ground  155  through the second diode  160 . 
     A neutral line  162  is configured to connect to the PMG neutral point  116 , wherein the neutral line  162  connects to a node  164  between the first DC input  138  and the second DC output  140 . A first capacitor  166  is connected between the first DC output  138  and the neutral line  162 . A second capacitor  168  is connected between the second DC output  140  and the neutral line  162 . The node  164  is connected to the first capacitor  166 , the second capacitor  168 , and the neutral line  162 . This node  164  can be connected to ground  155 , as shown in  FIG.  1   , so a negative DC voltage can be output from the second DC output  140 , and a positive DC voltage can be output from the first DC output  138 . The neutral point  116  is therefore connected as a floating point between the first and second DC outputs  138 ,  140 . 
     It is also contemplated as shown in  FIG.  2    that the second DC output  140  can be connected to ground  155  instead. The node  164  in this case is configured to output an intermediate positive DC voltage (VDC, half way between the voltage +2 VDC of the DC output  138  and ground of the DC output  140 ). 
     By having the second reactor  126 , the negative half of the PMG output voltage can be utilized to establish a DC link. The topology shown in  FIG.  1   , assume a +/- VDC, where the center point (node  164 ) of the output is the reference or return path. By utilizing the negative half of the waveform, the PMG size can be reduced relative to systems with only one saturable reactor. Another potential benefit of this topology is that it lends itself towards variable frequency systems. The reactors  118  and  126  can be to be sized for the highest operating speed, but in order to help limit voltage, one half of the reactor can be turned off for high speed operation. This can allow the PMG sizing to be reduce and allow for better voltage control at high speed. It is also contemplated that the system  100  can be configured to limit voltage output for high speed range (e.g., 2:1) applications while limiting the PMG sizing. The reactor topology disclosed herein can also be more cost effective than switching power supplies. 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for direct current (DC) power from an alternating current (AC) generator, e.g. aboard an aircraft. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.