Variable-Speed Motor Start Method Using Oscillating Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for starting electric motors, particularly synchronous or asynchronous motors, face challenges when the drive train becomes blocked due to contamination, leading to incorrect start direction if negative torque is applied to break the blockage.
Innovation Solution
A method involving continuous changes in positive torque frequency to utilize resonance effects and break free the blockage, ensuring the motor starts in the correct direction by using a frequency converter to control the motor speed and applying a positive torque with varying frequencies, specifically using the current component Iq along the q-axis with periodic oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a maximum starting torque in alternating direction of rotation is applied to break the blockage, then the blockage can be overcome, but the drive can briefly start running in the wrong direction
Solution Approach 1:
The patent applies mechanical vibration through oscillating torque to break the blockage. Instead of using alternating positive and negative torque, the invention superimposes an oscillating component on a positive torque reference value, creating a vibrating torque that loosens the blockage while maintaining unidirectional rotation tendency, thus preventing reverse direction startup
Solution Approach 2:
The patent employs periodic action by superimposing an oscillating torque component with a specific frequency on the positive torque reference. This periodic oscillation continuously acts on the blocked shaft, gradually overcoming the static friction and blockage forces while keeping the overall torque direction positive, ensuring the motor starts in the correct direction after blockage removal
2Force
If mechanical force is applied to the shaft to release the blockage, then the blockage can be removed, but the system requires manual intervention and downtime
Solution Approach 1:
The patent implements self-service by enabling the motor controller to automatically detect blockage conditions and apply the oscillating torque breakdown procedure without external intervention. The system monitors current and torque parameters, identifies blockage, and executes the loosening sequence autonomously, eliminating the need for manual shaft manipulation and reducing downtime
3Reliability
If the shaft is blocked due to contamination, then the pump or drive must be dismantled and cleaned, but this increases maintenance complexity and downtime
Solution Approach 1:
The patent applies preliminary action by detecting blockage conditions early through monitoring current and torque parameters, and automatically executing the oscillating torque breakdown procedure before the blockage becomes severe. This preventive approach allows the system to clear minor blockages in-situ without requiring dismantling or extensive maintenance intervention
Solution Approach 2:
The patent replaces manual mechanical intervention (dismantling, cleaning, reassembly) with an automated electrical control solution. The motor controller generates the oscillating torque sequence electronically, and the system uses electrical parameter monitoring to detect blockage, substituting the entire mechanical maintenance process with an automated electro-mechanical breakdown procedure
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
Efficient and quick removal of blockages without causing the motor to start in the wrong direction, ensuring reliable operation by maintaining a positive torque and utilizing resonance effects for effective loosening.
Implementation Method 1
Due to the continuous variable frequency change in the torque, the fixed drive shaft can be broken loose by utilizing so-called resonance effects
Data Source
Figure 1
AI summary
The invention relates to a method for starting a variable-speed electric motor, wherein upon detection of locking of the motor shaft a positive torque is applied to the motor shaft, and wherein the positive torque is continuously modified with different frequencies to overcome the locking.