H-Bridge Coil Current Decay for Degaussing Shutdown Protection
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Solution Overview
Problem
Conventional ship degaussing systems face significant challenges in safely dissipating energy feedback from inductive coils during shutdown, leading to potential damage due to the reliance on large, expensive, and unreliable external energy absorption circuitry.
Innovation Solution
The implementation of an active energy absorption method within the power converter itself, where the H-bridge converter operates in a protection mode by continuously turning on or off specific switches to circulate and decay the initial current within the converter and coil, eliminating the need for external dissipation components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large external energy absorption circuitry is used to dissipate feedback energy, then the power converters are protected from damage, but the system size, weight, and cost increase significantly
Solution Approach 1:
The energy absorption function is merged with the power converter itself by utilizing existing internal components (switches, inductors, capacitors) rather than adding separate external absorption circuitry. The controller manages these internal components to dissipate feedback energy, eliminating the need for large external resistors or absorption devices.
Solution Approach 2:
The power converter components are made multi-functional by enabling them to perform both their primary power conversion function and the secondary function of absorbing feedback energy during shutdown. The switches and energy storage elements serve dual purposes: converting power during operation and dissipating stored energy during shutdown without requiring dedicated absorption components.
2Ease of manufacture
If passive TVS diodes are used for energy absorption, then the circuit design is simple, but the system reliability is low due to diode failure
Solution Approach 1:
The power converter uses its own controlled switching elements and energy storage components to absorb and dissipate feedback energy, rather than relying on passive TVS diodes that can fail. The controller actively manages the internal components to ensure energy dissipation, making the system self-sufficient and eliminating single-point failures associated with passive protection devices.
3Loss of energy
If active energy absorption circuitry with monitoring systems is used, then energy dissipation is effective, but the system complexity and reliability issues increase
Solution Approach 1:
The controller that already exists for normal power converter operation is made multi-functional by programming it to also manage the shutdown and energy dissipation process. The same controller that regulates power conversion during operation now also controls the switching sequence during shutdown to dissipate feedback energy, eliminating the need for separate monitoring and control circuitry.
Solution Approach 2:
The controller uses feedback from the system state during shutdown to manage the energy dissipation process. By monitoring the shutdown condition and controlling the switching elements accordingly, the system effectively dissipates feedback energy while maintaining simple control logic that is already present in the power converter's normal operation control.
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 approach effectively prevents high oscillations and safely dissipates feedback energy, reducing the risk of damage to the system components and eliminating the need for costly external energy dissipation circuitry.
Implementation Method 1
large inductive coils that have the potential to store significant amounts of energy when energized
Implementation Method 2
Active energy absorption circuitry relies on a complex and unreliable active monitoring system to activate the circuitry, usually resistors, to convert the feedback energy to heat
Data Source
AI summary
An apparatus includes a power converter having switches coupled to input voltage rails and to opposing terminals of a coil to be energized. The switches are configured to be turned ON or OFF to conduct or block current, respectively, responsive to switch control signals. The apparatus also includes a controller to generate the switch control signals to compel the power converter to selectively operate (i) in a normal mode in which the switches are periodically turned ON and OFF to supply current from the input voltage rails to the coil to energize the coil, and (ii) in a protection mode in which first switches are continuously turned ON, and second switches are continuously turned OFF, to interrupt the current, and to circulate an initial current, flowing in the coil when the protection mode is entered, through the power converter and the coil so that the initial current decays toward zero.