BLDC Compressor Starting with Hysteresis Current Control
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Solution Overview
Problem
Existing starting methods for BLDC motors in refrigerating systems with high load and non-equalized pressure conditions are inefficient, leading to slow torque control and potential overcurrent issues due to reliance on voltage adjustment and inadequate current control.
Innovation Solution
A two-levels discrete fixed-time or fixed-frequency hysteresis current controller is used to drive a BLDC motor with trapezoidal shaped induced voltages, employing an inverter bridge with only one current sensor in the busbar, controlled by a processing unit and analog-digital converter, to achieve maximum torque and prevent overcurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If voltage adjustment method is used for starting BLDC motor, then the control is simple, but the torque control is slow and overcurrent occurs under high load conditions
Solution Approach 1:
The patent changes the control parameter from voltage adjustment to direct current control. By controlling the current amplitude and phase directly through the inverter bridge, the system achieves fast torque response without the delays inherent in voltage-based control methods, particularly under high load starting conditions
Solution Approach 2:
The patent implements current feedback control by measuring the actual current through the current sensor and comparing it with the reference current. The controller adjusts the inverter bridge switching based on the current error signal, enabling closed-loop current control that prevents overcurrent while maintaining fast torque control
2Device complexity
If one current sensor is used in the busbar, then the device complexity is reduced, but the current control precision is insufficient for high load conditions
Solution Approach 1:
The patent uses the busbar as an intermediary measurement point. By placing the current sensor in the busbar, the system measures the total current supplied to the motor, which serves as a reliable proxy for phase current control. This intermediary measurement approach maintains simplicity while providing sufficient control precision when combined with appropriate control algorithms
Solution Approach 2:
The single current sensor in the busbar serves multiple functions: it measures the total supply current for control feedback, detects overcurrent conditions for protection, and provides information for starting control. This multi-functional use of a single sensor achieves precise current control without requiring separate sensors for each function
3Productivity
If maximum current is applied to generate maximum torque, then the starting performance is improved, but overcurrent damage to the motor occurs
Solution Approach 1:
The patent implements dynamic current control where the current reference and limits are adjusted based on the motor's operating state. During starting, the controller dynamically adjusts the current amplitude and switching frequency to generate maximum torque while preventing overcurrent damage. The control parameters change continuously according to the motor's speed and load conditions
Solution Approach 2:
The patent establishes current limits and protection mechanisms before overcurrent damage can occur. The controller pre-defines maximum current thresholds and implements protective switching that activates before damaging current levels are reached. This beforehand cushioning ensures that even under high load starting conditions, the motor is protected from overcurrent damage
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 method ensures fast and effective torque control, preventing overcurrents even under high load conditions, by using a two-level current control strategy that adjusts current limits and switching times to manage motor current effectively.
Implementation Method 1
brushless direct current three-phase motor (BLDC), having voltages induced in a trapezoidal shape
Data Source
AI summary
The present invention refers to a starting method with two-levels modified and discrete fixed-time or fixed-frequency hysteresis current controller, under high load conditions, of a BLDC motor (10) with trapezoidal-shaped induced voltages, wherein the BLDC motor (10) is driven by an inverter bridge (30) with only one current sensor (20) positioned in the busbar, controlled by means of a processing unit associated to an analog-digital converter, wherein the novelty basically comprises the fact that:the intensity of the BLDC motor current (Im) is controlled by means of the two-levels and discrete fixed-time or fixed-frequency hysteresis current controller.