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Originally posted by garrettm4
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For those who would like to know how I constructed my solid-state SPV generator take a glance at the circuit diagram:
While there are many improvement to make, the basic design does works, although it is a bit complex to control all the switching elements.
Some insight into how and when the switching should take place consider the diagram below:
(This diagram was made with Microsoft Mathematics for those who would like to graph the waves under study, I have the worksheet saved if anyone wants it)
The, 2x frequency, blue square wave shown is one of the control signals for the circuit and for the sake of discourse we will say it controls the MagAMP in the above circuit diagram. The green sine wave is that of voltage and is in a quadrature relationship with the purple sine wave of current and the black, 2x frequency, is that of power, something that will interest you is that the power waveform goes into both the top and bottom half of the graph, this represents reactive power or a surging to and fro of stored and returned energy. Something to take note of, is if, the black waveform is on one side or the other, top or bottom of graph with respect to the x axis, this would mean unilateral transfer of power is taking place, or simply power dissipating into a load. Dependent upon the actions taking place in the circuit, the power waveform can be any place between the two points of top/bottom or in between. Thus you could see in a device that returns more power than it consumes, such as in the circuit above, that the power wave form will be smaller on top and bigger down below where it is situated on the x axis. Thus the source input becomes a load and the load now a source. The understanding that power is a cross product of voltage and current, with phase angle taken into account, and the direction it flows is fundamental in making one of these devices work. Now back to the blue control waveform as seen above, the current pulsed into the control winding of the MagAMP controls its relative saturation or capacity at any one moment in time. Thus you would saturate the core from the zero crossing / rise to peak portion of the purple wave and desaturate at the peak to fall / zero crossing portion. Thus inductance changed from L0, low inductance to L1, high inductance at the proper times. As for the switched capacitor as can be seen in the circuit above, you would have a separate control signal that would be out of phase with the one controlling the inductance. Thus the capacitance would go from CO, large value from zero crossing/ rise to peak and to C1, small value at peak to fall / zero crossing.
What you will notice is that there will be two resonant frequencies C1 & L0 and L1 & C0. Caused from C1 discharging into L0 and L1 discharging into C0.
Take into consideration the following equations:
The first one shows the discharge of C1 into L0 with currentA and voltageB and the other shows L1 discharge into C0 at currentA and voltageA, this caused from the fact that current remained the same during the point of parameter change for inductance but voltage changed because both capacitors are now in parallel. With the law of conservation of energy taken into mind, these equations state, that the maximum energy stored could only be that of the source energy, or L1 for C0 and C1 for L0. Thus excess energy can only come from the parameter change and nothing else.
Note that if you can get one of these devices to work, they simply self destruct within a few seconds of operation, if you loop the two equations above you will see a exponential rise in oscillatory energy. Thus you need to properly load the circuit to remove the excess energy from the oscillatory system. The concept of positive feedback to build the oscillations and a negative feedback mechanism to control the magnitude of the output comes to mind. The best method would be to alter the phase angles of the control circuits and not their frequency so as to slightly alter where on the curves of the voltage and current you choose to change your parameter. So a microcontroller could, with some hard work, tame the circuit, at least in principle.
While there are many improvement to make, the basic design does works, although it is a bit complex to control all the switching elements.
Some insight into how and when the switching should take place consider the diagram below:
(This diagram was made with Microsoft Mathematics for those who would like to graph the waves under study, I have the worksheet saved if anyone wants it)
The, 2x frequency, blue square wave shown is one of the control signals for the circuit and for the sake of discourse we will say it controls the MagAMP in the above circuit diagram. The green sine wave is that of voltage and is in a quadrature relationship with the purple sine wave of current and the black, 2x frequency, is that of power, something that will interest you is that the power waveform goes into both the top and bottom half of the graph, this represents reactive power or a surging to and fro of stored and returned energy. Something to take note of, is if, the black waveform is on one side or the other, top or bottom of graph with respect to the x axis, this would mean unilateral transfer of power is taking place, or simply power dissipating into a load. Dependent upon the actions taking place in the circuit, the power waveform can be any place between the two points of top/bottom or in between. Thus you could see in a device that returns more power than it consumes, such as in the circuit above, that the power wave form will be smaller on top and bigger down below where it is situated on the x axis. Thus the source input becomes a load and the load now a source. The understanding that power is a cross product of voltage and current, with phase angle taken into account, and the direction it flows is fundamental in making one of these devices work. Now back to the blue control waveform as seen above, the current pulsed into the control winding of the MagAMP controls its relative saturation or capacity at any one moment in time. Thus you would saturate the core from the zero crossing / rise to peak portion of the purple wave and desaturate at the peak to fall / zero crossing portion. Thus inductance changed from L0, low inductance to L1, high inductance at the proper times. As for the switched capacitor as can be seen in the circuit above, you would have a separate control signal that would be out of phase with the one controlling the inductance. Thus the capacitance would go from CO, large value from zero crossing/ rise to peak and to C1, small value at peak to fall / zero crossing.
What you will notice is that there will be two resonant frequencies C1 & L0 and L1 & C0. Caused from C1 discharging into L0 and L1 discharging into C0.
Take into consideration the following equations:
The first one shows the discharge of C1 into L0 with currentA and voltageB and the other shows L1 discharge into C0 at currentA and voltageA, this caused from the fact that current remained the same during the point of parameter change for inductance but voltage changed because both capacitors are now in parallel. With the law of conservation of energy taken into mind, these equations state, that the maximum energy stored could only be that of the source energy, or L1 for C0 and C1 for L0. Thus excess energy can only come from the parameter change and nothing else.
Note that if you can get one of these devices to work, they simply self destruct within a few seconds of operation, if you loop the two equations above you will see a exponential rise in oscillatory energy. Thus you need to properly load the circuit to remove the excess energy from the oscillatory system. The concept of positive feedback to build the oscillations and a negative feedback mechanism to control the magnitude of the output comes to mind. The best method would be to alter the phase angles of the control circuits and not their frequency so as to slightly alter where on the curves of the voltage and current you choose to change your parameter. So a microcontroller could, with some hard work, tame the circuit, at least in principle.
I understand the possibility of using the Magamp to vary the inductance successfully, but do you really think that using two static caps being switched in and out of position will really work as a true capacity parameter variation?
I have yet to do any extensive analyzing of the numbers, but from all of the math that I've worked with in the "Charge Conserving Capacitive Spring" thread suggests that you actually need to move capacitor plates in order to produce the effect that we are looking for.
Dave
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