Contactor Drive Current Source Control with Economizer Delay
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Solution Overview
Problem
Conventional electrical power generation and distribution system (EPGDS) contactors face issues with economizer failure leading to potential de-energization or undetectable conditions due to pull-in current being below the overcurrent threshold, necessitating improved systems and methods for reliable operation.
Innovation Solution
A system and method utilizing a current source control circuit with a delay circuit and Zener diode configuration to manage current levels in EPGDS contactors, transitioning from a higher pull-in current to a lower hold current after a delay, ensuring stable contactor operation without relying on on/off switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an economizer is implemented to reduce power dissipation by switching from high current pull-in mode to lower current hold mode, then energy efficiency is improved, but the risk of undetectable economizer failure increases when pull-in current is below the overcurrent threshold
Solution Approach 1:
A current sense resistor is introduced as an intermediary element in series with the coil to indirectly measure the pull-in current. This resistor converts the current into a measurable voltage drop, enabling the control circuit to detect whether the pull-in current exceeds the threshold without directly measuring the current itself. This intermediary measurement mechanism allows reliable detection of economizer failures even when the pull-in current is below the overcurrent threshold.
Solution Approach 2:
The system implements a feedback mechanism where the voltage across the current sense resistor is continuously monitored by the control circuit. When the measured voltage indicates that the pull-in current is below the threshold, the control circuit receives feedback and prevents the economizer from activating, thereby maintaining the contactor in a safe state and avoiding undetectable failure conditions.
2Use of energy by moving object
If the pull-in current is reduced to be below the overcurrent threshold to enable economizer operation, then energy consumption is reduced, but the ability to detect economizer failure is lost
Solution Approach 1:
The current sense resistor serves as a mediator that enables indirect measurement of the pull-in current by measuring the voltage drop across it. This allows the system to operate with reduced pull-in current below the overcurrent threshold while still maintaining the capability to detect economizer failures through the voltage measurement.
Solution Approach 2:
The system replaces direct current measurement (which would require complex current sensing infrastructure) with a simpler voltage measurement approach using the current sense resistor. This substitution enables failure detection through standard voltage sensing circuits while allowing the pull-in current to be reduced for energy efficiency.
3Device complexity
If conventional on/off switch control is used for the coil drive, then the system is simple, but it cannot provide stable current supply to prevent unintended de-energization
Solution Approach 1:
The system transitions from static on/off switch control to dynamic pulse-width modulation (PWM) control. The PWM controller dynamically adjusts the duty cycle of the drive signal to maintain a stable average current through the coil, preventing unintended de-energization while allowing for efficient economizer operation. This dynamic control approach provides superior current stability compared to simple on/off switching.
Solution Approach 2:
The system changes the control parameter from binary on/off states to a continuous duty cycle parameter in PWM control. By varying the duty cycle, the system can precisely control the average current through the coil, ensuring stable operation and preventing unintended de-energization while maintaining compatibility with the economizer function.
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 prevents unintended de-energization of contactors by ensuring a stable current supply, enhancing the reliability of EPGDS contactors in aerospace applications by using a current source control circuit with a delay mechanism.
Implementation Method 1
The Zener diode can have a Zener voltage below which the Zener diode inhibits current flowing from the voltage source to the resistor and the BJT
Implementation Method 2
a bipolar junction transistor (BJT). The Zener diode can be connected between the voltage source and the resistor, and the resistor can be connected between the Zener diode and the BJT
Implementation Method 3
The current source control circuit can include a linear regulator based current source. The linear regulator based current source can include an operational amplifier
Implementation Method 4
A pass element includes a source, a drain, and a gate, wherein the drain is electrically connected to the coil, and wherein the coil is in series between the pass element and ground
Data Source
AI summary
A system includes a contactor operatively connected to a coil for actuating the contactor to open and close a circuit. A pass element includes a source, a drain, and a gate, wherein the drain is electrically connected to the coil, and wherein the coil is in series between the pass element and ground. A voltage source is connected to the source of the pass element to pass current into the coil when the pass element is in a pass state. A current source control circuit with economizer is operatively connected to the gate of the pass element. A delay circuit is operatively connected to the current source control circuit with economizer and to a command line to command a lower current for holding the contactor closed after a delay has expired for the contactor to transition.