摘要:
A microcontroller-based system to detect ground-fault and grounded-neutral conditions in a monitored circuit of an electrical distribution system having line and neutral conductors. The system includes a single sensor producing an output signal responsive to current flow in both the line and neutral conductors of the monitored circuit, and a microcontroller receiving the sensor output signal and initiating the generation of a circuit status signal indicating one of a normal operating condition, a ground-fault condition or a grounded-neutral condition in the monitored circuit. The microcontroller is programmed to continuously test for ground-fault conditions by evaluating the sensor output signal and, at selected intervals, test for grounded-neutral conditions by evaluating the sensor's output signal response to a microcontroller initiated ping in the sensor circuit.
摘要:
An economical digital voltage sag compensator for overcoming sags in distributed electrical power. The voltage sag compensator employs an inexpensive micro-controller, a full wave bridge rectifier, a DC power supply, a voltage divider and an output switch. The micro-controller continuously monitors and evaluates, with respect to a setpoint measured in volt-seconds, the rectified DC voltage. At regularly spaced trigger events, as determined by the micro-controller, the micro-controller concurrently monitors the rectified DC voltage, evaluates the monitored voltage with respect to the setpoint, produces an output signal and sends that output signal to the output switch. The output switch supplies an electrical device, connected electrically in series with the full wave bridge rectifier and the output switch, with a constant average current of sufficient level to maintain the electrical device in a desired operating condition. The constant average current is obtained by applying constant volt-seconds to the electrical device. The circuit also provides overvoltage protection to the electrical device.
摘要:
Methods of determining a quantity of rotor slots in an induction motor are disclosed. An approximate slip is calculated according to an approximate slip function. A fundamental frequency is calculated from a representation of the voltage signal. A saliency frequency is calculated from a representation of the current signal. For each rotor slots index in a set of rotor slots indices, a slip estimate is calculated according to a slip estimation function. A slip estimation error signal is calculated. A rotor slots performance surface representative of an aggregate of the slip estimation error signals is calculated. A rotor slots quantity equal to the rotor slots index corresponding to a minimum of the rotor slots performance surface over at least a portion of the set of the rotor slots indices is defined.
摘要:
A method and apparatus to provide estimates of electrical parameters for line-connected induction motors during either steady-state or dynamic motor operations. The electrical parameters are calculated from the motor nameplate data and voltage and current measurements. No speed sensors or electronic injection circuits are needed. The method can be divided into 4 major steps. First, complex space vectors are synthesized from voltage and current measurements. Second, the instantaneous rotor speed is detected by calculating the rotational speed of a single rotor slot harmonic component with respect to the rotational speed of the fundamental frequency component. Third, the positive sequence fundamental frequency components are extracted from complex space vectors. Finally, least-squares estimates of the electrical parameters are determined from a dynamic induction motor equivalent circuit model.
摘要:
A method and apparatus to dynamically and adaptively demodulate induction motor instantaneous rotor slot harmonic frequency for line-connected squirrel-cage polyphase induction motors. The instantaneous rotor slot harmonic frequency carries essential information on the instantaneous rotor speed. Based on a correlation between the motor's input power and its rotor slot harmonic frequency, a dynamically varying carrier frequency is computed and used in a rotor slot harmonic frequency detector. The rotor slot harmonic frequency detector is based on a superheterodyne principle. It contains a generalized linear-phase low-pass filter, whose bandwidth is estimated dynamically by a filter bandwidth estimator. The rotor slot harmonic frequency detector also includes a latency compensator, which receives the dynamically varying carrier frequency signal and synchronizes it with the output of a frequency demodulator.
摘要:
The invention provides an elevator system for controlling movement of an elevator car with respect to guide rails in an elevator hoistway, having a force-estimation or position-scheduled current command controller and a magnet driver circuit without the need for a flux sensor. The force-estimation or position-scheduled current command controller responds to a force command signal, and further responds to a sensed gap signal, for providing a force-estimation or position-scheduled current command controller signal as a current command to the magnet driver circuit. The magnet driver circuit responds to the force-estimation or position-scheduled current command controller signal, for providing a magnet driver circuit signal to control said horizontal movement of the elevator car with respect to the guide rail in the elevator hoistway, whereby the horizontal movement of the elevator car is controlled without sensing magnetic flux. Other applications include any system that uses an electromagnet to produce an attractive or repulsive force across a large air gap, such as magnetic levitation trains or shuttles, and magnetic bearings.
摘要:
A method and apparatus to dynamically and adaptively demodulate induction motor instantaneous rotor slot harmonic frequency for line-connected squirrel-cage polyphase induction motors. The instantaneous rotor slot harmonic frequency carries essential information on the instantaneous rotor speed. Based on a correlation between the motor's input power and its rotor slot harmonic frequency, a dynamically varying carrier frequency is computed and used in a rotor slot harmonic frequency detector. The rotor slot harmonic frequency detector is based on a superheterodyne principle. It contains a generalized linear-phase low-pass filter, whose bandwidth is estimated dynamically by a filter bandwidth estimator. The rotor slot harmonic frequency detector also includes a latency compensator, which receives the dynamically varying carrier frequency signal and synchronizes it with the output of a frequency demodulator.
摘要:
Methods and devices are presented herein for estimating induction motor inductance parameters based on instantaneous reactive power. The induction motor inductance parameters, e.g., the stator inductance and the total leakage factor, can be estimated from motor nameplate data and instantaneous reactive power without involving speed sensors or electronic injection circuits. In one embodiment, the method includes: measuring voltages and currents; converting the measured voltages and currents into discrete-time voltage and current samples by analog-to-digital converters; synthesizing a complex voltage from the discrete-time voltage samples; synthesizing a complex current from the discrete-time current samples; acquiring and storing motor nameplate data; detecting instantaneous rotor speed by calculating an instantaneous rotor slot harmonic frequency with respect to an instantaneous fundamental frequency; calculating, via an induction motor inductance estimator, the motor's instantaneous reactive power and other intermediate quantities; and outputting the stator inductance and the total leakage factor.
摘要:
Methods of determining a quantity of rotor slots in an induction motor are disclosed. An approximate slip is calculated according to an approximate slip function. A fundamental frequency is calculated from a representation of the voltage signal. A saliency frequency is calculated from a representation of the current signal. For each rotor slots index in a set of rotor slots indices, a slip estimate is calculated according to a slip estimation function. A slip estimation error signal is calculated. A rotor slots performance surface representative of an aggregate of the slip estimation error signals is calculated. A rotor slots quantity equal to the rotor slots index corresponding to a minimum of the rotor slots performance surface over at least a portion of the set of the rotor slots indices is defined.
摘要:
A method of determining a slip estimate associated with an induction motor through analysis of voltage and current signals. A fundamental frequency is calculated from a representation (e.g., complex representation) of the voltage signal, and a saliency frequency is calculated from a representation of the current signal. An estimation of slip quantity is calculated according to a slip estimation function that includes the saliency frequency, a saliency order, the fundamental frequency, a quantity of rotor slots, and a quantity of poles of the motor.