Motor Control System Using Short-Circuit Pulse Detection
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Solution Overview
Problem
Existing motor control systems face challenges in determining the angular position and speed of a rotor, especially after a power outage or when the motor is already spinning before drive control commences, leading to uncertainties in energy management and motor control.
Innovation Solution
A method involving short-circuiting motor windings to generate current pulses, identifying peaks to estimate rotation frequency, and applying magnetizing pulses to ensure reliable estimation, using a controller with a frequency estimator and phase locked loop to determine orthogonality of current vectors for accurate motor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If short-circuiting windings is used to estimate motor speed, then speed estimation can be performed without external sensors, but the estimation may be unreliable when the motor is at standstill or with low stored energy
Solution Approach 1:
The system applies a magnetizing pulse before performing speed estimation to ensure the motor has sufficient stored energy. This preliminary action prepares the motor state so that subsequent short-circuiting operations can reliably generate measurable current pulses for accurate frequency detection, regardless of the motor's initial state.
Solution Approach 2:
The motor's own windings and stored energy are utilized to generate the measurement signals. By short-circuiting the windings and detecting the resulting current pulses, the system uses the motor itself as the measurement source, eliminating the need for external sensors while maintaining measurement capability across different operating states.
2Ease of operation
If the motor is short-circuited to generate current pulses for frequency estimation, then non-contactless speed sensing is achieved, but energy is extracted from the motor
Solution Approach 1:
The system applies a magnetizing pulse that may exceed the minimum required energy level to ensure reliable frequency estimation. This excessive action guarantees sufficient stored energy for multiple short-circuiting operations and accurate measurement, compensating for the energy extracted during sensing operations.
Solution Approach 2:
The system dynamically adjusts the magnetizing pulse parameters (amplitude, duration) based on the motor's initial state. When the motor is at standstill or with low stored energy, higher energy pulses are applied. When the motor already has sufficient energy, smaller pulses are used, optimizing the balance between measurement reliability and energy conservation.
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 approach allows for reliable estimation and control of motor speed and direction, ensuring smooth energy management and motor operation without disturbing stored energy, even in uncertain initial conditions.
Implementation Method 1
repeatedly short-circuiting at least some windings of the motor in order to generate a plurality of short circuit current pulses
Implementation Method 2
applying a magnetising pulse to the motor
Data Source
AI summary
A method and apparatus for catching a rotating motor is described. Switches (typically the lower switches) of an inverter of a motor drive circuit are short-circuited for a brief period of time. The pulses generated by this process are analyzed to determine the speed and direction of rotation of the motor. The pulses are checked to determine whether they are orthogonal. If they are, the motor velocity determination is deemed to be reliable and then motor is magnetized and normal motor control can be resumed. If not, the motor velocity determination is deemed to be unreliable and a magnetization pulse before the velocity determination step is repeated.