Load Impedance Circuit Using Switched Square-Wave Injection
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Solution Overview
Problem
Existing impedance measurement systems for plasma thrusters and similar loads face challenges with large current fluctuations and unstable operation due to leakage inductance in series injection transformers and inability to accurately measure impedance with parallel injection transformers.
Innovation Solution
A circuit with a signal injector, controllable switch, and voltage drop device connected in parallel, injecting an approximately square wave perturbation and using a computing device to determine impedance by analyzing voltage and current measurements, with the ability to control the switch based on frequency and utilize a plurality of serially connected diodes for voltage drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a series injection transformer is used to measure impedance, then the impedance can be determined by injecting current, but the breathing mode current fluctuations can overload the power amplifier
Solution Approach 1:
A current transformer is introduced as an intermediary device between the power amplifier and the plasma load. The current transformer couples the amplifier to the load through magnetic coupling, allowing impedance measurement while isolating the amplifier from direct exposure to breathing mode current fluctuations. This mediator enables accurate impedance determination without overloading the power amplifier.
2Measurement precision
If a series injection transformer is used, then impedance measurement is possible, but the leakage inductance creates too much impedance for stable plasma operation
Solution Approach 1:
The current transformer serves as a mediator that provides magnetic coupling between the power amplifier and plasma load without introducing significant leakage inductance into the plasma circuit. This intermediary approach enables impedance measurement while maintaining stable plasma operation by avoiding the excessive impedance introduced by traditional series injection transformers.
3Stability of the object's composition
If a parallel injection transformer with capacitor is used, then breathing mode current is reduced, but the low impedance power source soaks up injected current preventing accurate measurement
Solution Approach 1:
The current transformer acts as an intermediary that enables current injection while preventing the power source from directly soaking up the injected current. Through magnetic coupling, the transformer allows the measurement of impedance without the low impedance power source interfering with the injected current signal, thereby maintaining measurement accuracy while reducing breathing mode current effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for accurate and stable impedance measurement of loads like plasma thrusters by minimizing voltage drop and handling breathing mode currents effectively, providing reliable impedance data without overloading the power amplifier.
Implementation Method 1
the voltage drop device includes a diode
Data Source
AI summary
An impedance measurement circuit includes a signal injector having a voltage input and a voltage output, a controllable switch, and a voltage drop device connected in parallel with the controllable switch between the voltage input and the voltage output. The voltage output is connected to a load. A voltage sensor is configured to measure a voltage across the load. A current sensor is configured to measure a current draw of the load. A computing device is configured to determine an impedance of the load at a frequency based on the measured voltage and the measured current. The computing device controls the switch based on the frequency.