Outboard Motor Two-Stage Contacting Device for Current Surge Limiting
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Solution Overview
Problem
Outboard drives with electric motors face issues such as high charging current surges from buffer capacitors, leading to sparking and potential fire hazards due to defective contacts, and the weight and space constraints of large batteries, as well as electromagnetic compatibility problems with long power supply lines.
Innovation Solution
The outboard drive incorporates a contacting device with two stages: the first stage includes a current-limiting element to manage high currents, and the second stage allows direct connection without additional components, while integrating the DC voltage source into the drive to shorten electrical paths and reduce ohmic losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If buffer capacitors are used in the electric motor system to buffer harmonics, then electromagnetic compatibility is improved, but high charging current surges occur when connecting the power source
Solution Approach 1:
The patent applies preliminary action by introducing a current-limiting element that is activated before the main power connection is established. The controller detects the connection state and gradually increases current flow, preventing surge currents from damaging the buffer capacitors or causing sparks before the system is ready to accept full power.
Solution Approach 2:
The patent uses an intermediary approach by inserting a current-limiting element between the power source and the buffer capacitors. This intermediary component controls the charging current flow, allowing the capacitors to charge safely without experiencing harmful current surges, while still achieving the desired electromagnetic compatibility.
2Area of stationary object
If batteries are housed inside the boat rather than directly on the outboard drive, then space on the drive is freed, but long power supply lines increase ohmic losses and electromagnetic interference
Solution Approach 1:
The patent extracts the power source from the outboard drive and places it inside the boat, freeing up space on the drive. However, this extraction creates the problem of long power lines, which the patent then addresses by implementing a two-stage connection system with current limiting to minimize the negative effects of the extended power supply path.
Solution Approach 2:
The patent applies dynamics by making the power connection adaptive rather than static. The two-stage connection system dynamically adjusts the current flow based on the connection state, initially limiting current when the connection is made and then transitioning to full power transmission once the connection is stable, thereby reducing energy losses despite the long cable length.
3Object-generated harmful factors
If a two-stage contacting device with current limiting is used, then charging current surges are prevented, but the device complexity increases
Solution Approach 1:
The patent segments the power connection process into two distinct stages: a first stage with current limiting for safe initial connection and capacitor charging, and a second stage for full power transmission. This segmentation allows the system to prevent harmful current surges while maintaining a relatively simple overall device structure by using a single contacting device that operates in different modes.
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 configuration prevents current peaks and charging surges, reduces weight and space requirements, and enhances electromagnetic compatibility by minimizing cable resistance and length, thus ensuring safer and more efficient power supply to the electric motor.
Implementation Method 1
a current-limiting element is connected between the connected DC voltage source and the power supply line... The current-limiting element, for example, an ohmic resistor, limits the flowing current
Data Source
Figure 1~2
Figure 3
AI summary
The drive has an electric motor (4), and a contact-making apparatus (7) that is operatively connected to a power supply line (6) for connecting a rechargeable battery (10). The contact-making apparatus has two contact stages, where a non-reactive resistance (12) is connected between the battery and the power supply line in one of the contact stages, and limits the current flowing from the battery to the motor or to a control unit (5). A space for accommodating the battery is provided within a housing (8). The battery is connected directly to the power supply line in the other contact stage.