Conveyor Frequency Converter Control for Overload and Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conveyor technology systems in the automotive industry face challenges in achieving sufficient overload capacity and noise reduction due to limitations in existing frequency converter controls, which often require larger and more costly converters to handle performance demands.
Innovation Solution
The control system dynamically adjusts the pulse frequency of the inverter based on load current and temperature, reducing frequency when power limits are exceeded and increasing it when demands decrease, allowing for higher output currents during overloads while minimizing noise through hysteresis-based switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the pulse frequency is increased to reduce noise in the audible range, then noise is reduced, but the power capacity of the semiconductor switches is reduced due to heat generation
Solution Approach 1:
The pulse frequency is made dynamically adjustable rather than fixed. The control device changes the pulse frequency depending on operating conditions - using higher frequencies during normal operation to reduce noise, and allowing lower frequencies during overload situations to maintain power capacity. This dynamic adaptation resolves the contradiction by making the frequency a variable parameter rather than a fixed compromise.
Solution Approach 2:
The invention changes the pulse frequency parameter based on the current operating state of the converter. During normal operation, the frequency is set higher to minimize audible noise. When overload conditions are detected, the frequency can be reduced to allow the semiconductor switches to handle higher currents. This parameter change enables the system to optimize for noise during normal operation while maintaining power capacity when needed.
2Temperature
If the output current is limited to maintain low heat generation at high pulse frequencies, then heat generation is reduced, but the overload capability is insufficient
Solution Approach 1:
The current limit is made dynamic rather than fixed. During normal operation, the converter operates with higher pulse frequencies and corresponding lower current limits to minimize heat generation. When overload conditions arise, the control device allows temporary exceedance of the normal current limit by reducing the pulse frequency, enabling the system to handle overload situations without permanent damage while maintaining efficient operation during normal conditions.
Solution Approach 2:
The invention allows periodic transitions between different operating modes - normal operation with higher frequencies and lower current limits, and overload mode with lower frequencies and higher current limits. This periodic switching between operating states enables the system to maintain low heat generation during normal operation while providing adequate overload capability when required, resolving the contradiction between continuous heat reduction and intermittent overload capability.
3Reliability
If a frequency converter of higher power level is used to provide sufficient overload capacity, then overload capability is improved, but the size and cost of the frequency converter increase
Solution Approach 1:
Instead of designing the converter for maximum power capacity at all times, the invention uses parameter changes to allow the same hardware to operate at different power levels as needed. The pulse frequency and current limit parameters are adjusted based on operating conditions, enabling a smaller, less expensive converter to provide both efficient normal operation and adequate overload capability that would otherwise require a larger converter design.
Data Source
Figure 1
Figure 2
AI summary
The method involves changing a pulse rate (fn) of current of a controllable inverter (2) based on a load-side output current (Ia) of a power converter (1). The pulse rate is reduced if power or speed sensing reference value (Isoll) of the output current of the power converter exceeds a pulse rate-dependant current threshold value (Imax). The pulse rate is increased to an adjusted resting frequency if the reference value of the output current falls below the current threshold value, where the output current of the power converter is detected as an actual value (Iist). An independent claim is also included for a power converter.