Centrifugal Pump Field Weakening Control
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Solution Overview
Problem
Centrifugal pump units with conventional frequency converter control are limited in utilizing maximum available electrical power across all operating ranges, as maximum speed is constrained by the maximum output voltage and duty cycle, leading to underutilization of hydraulic power in certain areas.
Innovation Solution
The centrifugal pump unit employs an alternative control strategy with field weakening in the drive motor, allowing speed increase beyond conventional limits without raising output voltage, and incorporates a voltage converter to minimize switching losses by varying the input voltage to the frequency converter, enabling full utilization of electrical power across all operating ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional frequency converter control is used with maximum output voltage and duty cycle, then maximum speed is achieved at one point of pump characteristic, but maximum electrical power cannot be utilized in other areas of pump characteristic
Solution Approach 1:
The patent applies parameter changes by modifying the load angle between current and magnetic rotor from the conventional 90 degrees to a range between 90 and 150 degrees. This parameter change enables field weakening control, which allows the motor to operate at speeds beyond the base speed while maintaining optimal power utilization across different pump characteristic areas. The control device dynamically adjusts the load angle based on operating conditions to maximize electrical power conversion to hydraulic power throughout the entire pump operating range.
2Power
If field weakening is applied to increase speed beyond conventional limits, then electrical power can be fully utilized, but control complexity increases
Solution Approach 1:
The control device implements feedback control by continuously monitoring operating conditions and dynamically adjusting the load angle to optimize power utilization. The controller receives feedback about the pump's operating point and modifies the motor control parameters accordingly, enabling automatic adaptation to different operating ranges without requiring complex manual intervention or multiple separate control systems.
3Power
If maximum output voltage and duty cycle are maintained, then base speed operation is efficient, but speed increase is limited in certain operating ranges
Solution Approach 1:
The patent applies dynamics by transitioning from a static control approach (fixed 90-degree load angle) to a dynamic control approach where the load angle varies between 90 and 150 degrees based on operating conditions. This dynamic adjustment enables the system to adapt to different speed and power requirements, allowing seamless transition between base speed operation and field weakening region operation to maintain optimal efficiency across the entire operating range.
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
This solution allows for increased hydraulic power in low flow-high pressure and high flow-low pressure areas, maximizing electrical power utilization without increasing the electrical load, thereby enhancing the pump's performance and efficiency across its entire operating range.
Implementation Method 1
a control device (6) having a frequency converter (8) for controlling the speed of the drive motor (4)
Implementation Method 2
field weakening is generated in the drive motor (4) in at least one control area, by which the speed of the drive motor (4) can be further increased
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The assembly has a control device controlling speed of an electric driving motor. The control device includes a frequency converter, is designed such that a weakened field is increased by the speed of the driving motor, and is generated in a control range (S3). The driving motor is provided with a permanent magnetic-rotor. The control device is designed such that the weakened field is generated, and a load angle of power is increased above 90 degree compared to a magnetic field of rotor, so that current and an induced counter voltage (E) does not exceed in a phase.