Normally Closed Relay Bypasses Resistor to Prevent Melting
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Solution Overview
Problem
Existing electromagnetic relays in engine starters experience issues with inrush current, leading to voltage drops and potential failure of electrical systems, and are prone to resistor melting due to continuous current flow when the motor drive signal is cut off, especially in cold conditions.
Innovation Solution
A normally closed electromagnetic relay design with a movable core and relay contacts that short circuit when de-energized to bypass the resistor, ensuring current flows directly to the motor without going through it, even if the motor drive signal is cut off, and allows full battery voltage to be supplied when needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a normally open electromagnetic relay is used to control inrush current, then the starting current can be controlled through the resistor, but the relay contacts may remain open due to signal line failure causing continuous current flow through the resistor and potential resistor melting
Solution Approach 1:
The patent inverts the normal relay contact state from normally open to normally closed. The relay contacts are configured to be closed during normal operation and open only when the relay coil is energized. This inversion ensures that if the motor drive signal is lost (relay coil deenergized), the contacts remain closed, allowing full current to flow to the motor without passing through the resistor, thereby preventing resistor melting while maintaining reliable operation.
2Reliability
If the relay contacts are kept open to control current through the resistor, then inrush current is limited, but full battery voltage cannot be supplied to the motor when needed
Solution Approach 1:
The patent implements dynamic switching of the relay contacts based on operational requirements. The contacts transition from closed state (during normal operation) to open state (when relay coil is energized and motor needs full power). This dynamic state change allows the system to adapt between current-limited mode and full power mode, ensuring both reliable current control and adequate motor power supply when needed.
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 prevents resistor melting and ensures stable engine starting by bypassing the resistor when the motor drive signal is lost, maintaining full voltage supply to the motor, thus improving start-up performance and durability.
Implementation Method 1
a relay coil disposed inside the hollow case, the relay coil producing magnetic attraction when energized
Implementation Method 2
a relay coil disposed inside the hollow case, the relay coil producing magnetic attraction when energized
Data Source
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AI summary
A normally-closed electromagnetic relay which may be used in controlling a supply of electric current to an automotive engine starter. The electromagnetic relay is equipped with a resistor (7) and a short circuit. The short circuit is created by closing of relay contacts (27,28,29) when a relay coil (19) is energized to establish an electric connection between ends of the resistor to supply the current from a battery (6) to an electric motor (3) without flowing through the resistor and opened by opening of the relay contacts when the relay coil is deenergized to supply the electric current from the battery to the electric motor through the resistor. If a motor drive signal line leading to the electromagnetic relay is disconnected when the relay coil is kept energized, it will cause the short circuit to be established to ensure the supply of current to the motor, which also avoids the melting down of the resistor.