Soil Compactor Converter Frequency Control for Battery Runtime
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Solution Overview
Problem
Battery-operated soil compaction devices face issues with reduced battery life, increased cooling requirements, and reduced running time due to the need for higher currents when the battery voltage drops, leading to thermal deterioration and motor slip.
Innovation Solution
A soil compaction device with a converter that adjusts the alternating voltage frequency based on the battery's state of charge, reducing the frequency when the voltage falls below a threshold to maintain consistent power and reduce motor current, thereby extending battery life and reducing cooling needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the battery voltage drops during operation, then the battery running time is extended, but the motor currents must be increased to maintain constant power
Solution Approach 1:
The converter device dynamically changes the output frequency parameter of the alternating voltage based on the battery voltage level. When battery voltage drops below the threshold, the converter reduces the output frequency from the control frequency to a reduced frequency, which allows the motor to operate at lower currents while maintaining adequate power delivery, thus extending battery running time without excessive current increases
2Duration of action of moving object
If the battery voltage drops during operation, then the battery running time is extended, but the cooling requirement increases due to higher currents
Solution Approach 1:
By reducing the output frequency of the alternating voltage when battery voltage drops, the motor operates at lower currents. This parameter change directly reduces the I²R losses and thermal generation in both the motor and battery, thereby extending battery running time while simultaneously reducing the cooling requirement
3Duration of action of moving object
If the battery voltage drops during operation, then the battery running time is extended, but the motor slip increases leading to thermal deterioration
Solution Approach 1:
The converter device adjusts the output frequency parameter in response to battery voltage changes. When voltage drops, the reduced frequency allows the motor to maintain better synchronization and reduce slip, thereby extending battery running time while preventing the thermal deterioration that would result from excessive slip at low voltages
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
The solution extends battery operating time, reduces cooling requirements, and prolongs battery life by maintaining consistent power and current draw, while alerting the operator to recharge needs.
Implementation Method 1
a converter device for converting a direct voltage obtainable from the energy storage device into an alternating voltage for the electric drive
Data Source
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AI summary
A soil compaction device is specified, comprising a working device (1) for generating a working movement for soil compaction; an electric drive (2) for driving the working device (1); an electrical energy store (3) for providing electrical energy for the electric drive (2); and a converter device (4) for converting a direct voltage obtainable from the energy store (3) into an alternating voltage for the electric drive (2).The converter device (4) is designed to provide the alternating voltage at a predetermined control frequency when the direct voltage drawn from the energy store (3) is present at a direct voltage value above a predetermined threshold voltage value; and to provide the alternating voltage at a reduced frequency which is lower than the control frequency when the direct voltage drawn from the energy store (3) is present at a direct voltage value equal to or below the threshold voltage value.