Contactor Freewheel Circuit Segmentation for Transistor Protection
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Solution Overview
Problem
Existing contactor circuits face issues with energy dissipation and voltage spikes leading to potential transistor breakdown, inefficient energy usage, and high power dissipation, particularly due to slow coil energy dissipation and high current requirements for maintaining contact closure.
Innovation Solution
A freewheel circuit design incorporating a first coil, a second coil in series with a first transistor, and a diode arrangement that ensures all current flows through the first coil, allowing for optimized closing and holding currents, with a second transistor and capacitor configuration to manage energy storage and dissipation for controlled contact opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is connected in inverse parallel across the relay coil to prevent transistor breakdown, then transistor protection is improved, but current dissipation becomes slow and contact opening becomes gradual
Solution Approach 1:
The patent divides the coil into two separate coils (first coil and second coil) that can be independently controlled. This segmentation allows different current paths to be established for closing and holding operations, enabling the first coil to provide strong closing current while the second coil provides controlled holding current, thus resolving the contradiction between protection and rapid opening.
Solution Approach 2:
The patent uses active components (transistors Q2 and Q3) to dynamically control the current flow through the coils. The transistors can be switched on and off to change the circuit configuration, allowing the system to transition between different states (closing, holding, opening) with optimized current characteristics for each state, preventing both transistor breakdown and ensuring rapid contact opening.
2Reliability
If closing current is continuously applied to maintain contact closure, then contact reliability is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic pulsing of the closing current through transistor Q1 while maintaining contact closure through the holding current path via transistor Q3. The closing current is applied in periodic pulses rather than continuously, reducing average power consumption while still ensuring reliable contact closure and maintenance through the coordinated action of both coils and transistors.
Solution Approach 2:
The patent changes the current parameters by using two different coils with potentially different inductances and resistance characteristics. The first coil is optimized for high current closing operation while the second coil is optimized for lower current holding operation, allowing the system to maintain contact reliability with reduced power consumption during the holding phase.
3Speed
If high current is used to ensure rapid contact closing, then closing speed is improved, but power dissipation and component stress increase
Solution Approach 1:
The patent segments the current function into two parts: the first coil provides high current for rapid closing, while the second coil provides lower holding current. This segmentation allows the system to achieve rapid closing when needed without sustaining high current, thereby reducing overall power dissipation and component stress while maintaining closing speed performance.
Solution Approach 2:
The closing current through the first coil is applied in periodic pulses rather than continuously. This periodic action delivers the necessary high current bursts to achieve rapid contact closing, then reduces current to lower levels for holding, thereby reducing average power dissipation and thermal stress on components while maintaining closing speed.
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 design reduces power loss, extends the duration of contact closure, enhances efficiency by ensuring 100% current utilization, and allows for reliable operation across a wide voltage range with lower component stress and cost, while preventing transistor damage from voltage spikes.
Implementation Method 1
A contactor, or relay, is an electromagnetic device operable to selectively open and close one or more electrical contacts in response to a voltage applied to a coil in the contactor
Implementation Method 2
a diode 6 has been connected in inverse parallel across relay coil 3. When transistor 2 is turned off, the voltage rise at the collector of transistor 2 will cause diode 6 to conduct and clamp the collector voltage to about 0.7 volts (V) above V1, preventing damage to transistor 2
Implementation Method 3
a capacitor 50, the value of which has been optimised to extend the non-conduction time of closing current V2 for a period of time
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A circuit (100) for use with a contactor including at least one contact is provided. The circuit includes a first segment (112) including a voltage source (108), a first coil (102), a second coil (104), and a first transistor (106), wherein the first segment is configured to selectively conduct a closing current through the first coil, the second coil, and the first transistor to close the at least one contact. The circuit further includes a second segment (124) including the first coil, a second transistor (120), and a first diode (122), wherein the second segment is configured to selectively conduct a holding current through the first coil, the second transistor, and the first diode to hold the at least one contact closed, and wherein the first diode is arranged such that substantially all current produced by the voltage source flows through the first coil.