Motor Drive Capacitor Discharge Control via Hysteresis
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Solution Overview
Problem
Existing motor driving apparatuses face challenges in controlling the electric energy supplied from a capacitor, leading to rapid discharge and difficulty in maintaining a desired current level from the power source, requiring large-capacity capacitors and interrupting power source current.
Innovation Solution
A motor driving apparatus with a converter, inverter, capacitor, and charge-discharge control circuit, including a current control means that uses hysteresis comparators and PWM control to manage discharge current based on input and output power values, ensuring efficient energy use and reducing capacitor capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electric energy stored in the capacitor is discharged rapidly to reduce power source current, then the current from the power source is reduced, but the capacitor cannot supply electric energy to the inverter for a sufficient period of time
Solution Approach 1:
The patent applies dynamic control by switching between two discharge modes (constant current mode and constant power mode) based on real-time operating conditions. The control circuit dynamically adjusts the discharge characteristics of the capacitor to match the instantaneous power demand of the inverter, thereby optimizing both current reduction and energy supply duration without requiring a large-capacity capacitor.
2Duration of action of moving object
If a large-capacity capacitor is used to store much electric energy, then the capacitor can supply energy for a longer period, but the capacitance and size of the capacitor increase
Solution Approach 1:
The patent uses dynamic discharge control to maximize the utilization of the capacitor's stored energy. By switching between constant current and constant power discharge modes based on real-time power demand, the system extracts energy more efficiently from the capacitor, extending the energy supply duration without increasing capacitor capacitance.
Solution Approach 2:
The patent changes the discharge parameters (current and power levels) dynamically based on operating conditions. The control circuit adjusts discharge current and power levels in real-time to match the inverter's instantaneous demands, thereby optimizing energy utilization and extending supply duration without requiring larger capacitor capacity.
3Power
If the switch of the discharge circuit is turned on to discharge capacitor energy, then the power source current is reduced, but the discharge is too rapid and energy is depleted quickly
Solution Approach 1:
The patent implements dynamic discharge control that adjusts the discharge rate based on real-time power demand. The control circuit monitors the instantaneous power requirements and switches between constant current and constant power modes, thereby reducing power source current effectively while preventing excessive energy depletion and extending capacitor energy supply duration.
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 effectively controls the electric energy supplied from the capacitor, optimizing energy use and reducing the power source current to a desired level, allowing for efficient operation and compliance with power source limitations.
Implementation Method 1
a capacitor connected in parallel in a link section between the converter and the inverter
Implementation Method 2
the current control means comprises a hysteresis comparator configured to feed discharge current from the charge-discharge control circuit
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
A motor driving apparatus comprises a charge/discharge control circuit for controlling charge to or discharge from a capacitor connected in parallel in a link section between a converter and an inverter, and a current control means for controlling discharge current from the charge/discharge control circuit. The current control means controls discharge current from the charge/discharge control circuit based on input current to the inverter or output current from the converter so that output current from the converter is equal to a prescribed value.