Brushless DC Motor Conduction Angle Control for Lower Switch Heat
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Solution Overview
Problem
In backpack-type blowers with brushless DC motors, a fixed conduction angle of 120 degrees can lead to significant power loss and heat generation in switch devices when operating at high duty ratios to maintain a target rotational frequency under high load conditions.
Innovation Solution
The electric work machine includes a controller that adjusts the conduction angle based on the actual and target rotational frequencies of the brushless DC motor, thereby reducing power loss in the switch devices and minimizing heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the conduction angle of switch devices is fixed at 120 degrees to control the brushless DC motor, then the motor can operate at the target rotational frequency, but significant power loss and heat generation occur in the switch devices under high load conditions
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed conduction angle to a variable conduction angle that adapts based on motor operating conditions. The controller dynamically adjusts the conduction angle of switch devices according to the actual rotational frequency and load conditions, enabling optimal performance across varying operational states while reducing power loss and heat generation in the switch devices.
2Speed
If the conduction angle is increased to maintain target rotational frequency under high load, then the motor speed is maintained, but heat generation in switch devices increases
Solution Approach 1:
The patent applies parameter changes by modifying the conduction angle parameter based on motor operating conditions. The controller adjusts the conduction angle dynamically, changing this critical parameter to optimize the balance between maintaining rotational frequency and minimizing heat generation in switch devices under varying load conditions.
3Ease of operation
If PWM signals are used to control switch devices with fixed conduction angle, then the motor can be controlled, but power loss increases when operating at high duty ratio
Solution Approach 1:
The patent applies dynamics by making the conduction angle adjustable based on duty ratio and operating conditions. The controller dynamically optimizes the conduction angle in response to PWM control signals and load conditions, enabling effective motor control while minimizing power loss in switch devices during high duty ratio operation.
Data Source
AI summary
An electric work machine in one aspect of the present disclosure includes an output shaft, a brushless DC motor, a first positive-side conduction path, a first negative-side conduction path, a first switch device, a manual switch, a rotation sensor, and a controller. The first switch device is on the first positive-side conduction path or the first negative-side conduction path. The controller controls a magnitude of a conduction angle based on an actual rotational frequency and a target rotational frequency of the brushless DC motor.