As evidenced by industrial surveys, stator-related failures account for a large percentage of faults in induction machines. The objective of this paper is to provide a survey of existing techniques for detection of stator-related faults, which include stator winding turn faults, stator core faults, temperature monitoring and thermal protection, and stator winding insulation testing. The root causes of fault inception, available techniques for detection, and recommendations for further research are presented. Although the primary focus is online and sensorless methods that use machine voltages and currents to extract fault signatures, offline techniques such as partial discharge detection are also examined. Condition monitoring, fault diagnostics, insulation testing, interlaminar core faults, partial discharge (PD), temperature monitoring, turn faults.

A Survey of Methods for Detection of Stator-Related Faults in Induction Machines

Woodworking machines including conductive cutters adapted to cut workpieces, and motors adapted to drive the cutters are disclosed. The machines also include a contact detection system adapted to detect contact between a person and the cutter, and to distinguish contact between the person and the cutter from contact between the workpiece and the cutter. The machines further include a reaction system adapted to cause a predetermined action to take place upon detection of contact between the person and the cutter by the contact detection system.

Detection system for power equipment

A patient support apparatus is provided. The patient support apparatus includes a plurality of therapeutic devices including a rotation device and a percussion-vibration device for carrying out rotation, percussion, and vibration therapy for a patient. The patient support apparatus includes a control system for controlling operation of the plurality of therapeutic devices. The control system comprises a touch-screen display segmented into a main menu portion and a data window portion. The therapeutic functions are represented by touch selectable buttons on the main menu portion. When any of these buttons are selected, a plurality of adjustable operating parameters appears in the data window portion. At the same time, the buttons corresponding to the therapeutic functions in the main menu portion remain visible such that an operator can easily select another therapeutic function. A method of tracking the therapeutic functions performed is provided. A rotation monitoring system and temperature control system of the patient support apparatus are provided. A display activation system is also provided.

Patient support apparatus

A joint endoprosthesis system has first and second prosthetic components. The second prosthetic component has a bearing surface. The interface of the bearing surface and the first prosthetic component defines the joint articulation. A signal source and sensor are affixed on opposite sides of the joint articulation. The signal source generates a first signal that is received by the sensor. The sensor generates a second signal that has a characteristic that varies depending on the distance between the sensor and the signal source. A transmitter transmits a signal. The signal has a characteristic that varies depending on the characteristic of the second signal. This system can be used to measure a dimension of the joint space and to determine whether a dimension of the joint space has changed over time. The system may alternatively use magnets and magnetic sensors.

In vivo joint space measurement device and method

A miter saw is disclosed having a base, a blade supported by the base, a detection system adapted to detect a dangerous condition between a person and the blade, and a reaction system associated with the detection system to cause a predetermined action to take place upon detection of the dangerous condition. The blade is rotatable, and moves into a cutting zone to cut a workpiece. The predetermined action may be to stop the blade from rotating, to create an impulse against movement of the blade into the cutting zone, or to cause the blade to move away from the cutting zone.

Miter saw with improved safety system

An antenna receives, by capacitive effect, a current of which the intensity is a function of the distance separating the antenna from an electrical power line. The other factors that influence the current are fixed, constant or are considered negligible. A measuring and conditioning circuit converts the current at the output of the antenna into a coded signal and transmits this coded signal to a control unit. The control unit compares the coded signal to predetermined values stored therein. Alarms are generated by the control unit when the current from the antenna exceeds the predetermined values.

Alarm system and method for detecting proximity of an object to electrical power lines

The method consists in positioning a probe in front of a pair of teeth provided on the face of the magnetic circuit of an electric machine. The probe has spaced apart magnetic prong portions having respective end faces adapted to match the teeth of the pair with the end faces in registry with the teeth. The prong portions are respectively provided with an excitation winding and a measurement winding. The excitation winding is excited to induce a magnetic flux in a test zone formed of the teeth in front of the probe and a portion of the magnetic circuit extending therebetween. The current flowing in the excitation winding and the voltage across the measurement winding are measured for calculating a resulting power which is indicative of the condition of the test zone. The apparatus is formed of the probe and electronics carrying out the above functions.

Apparatus and method for evaluation a condition of a magnetic circuit of an electric machine

A method for dynamic and non-contact measurement of the displacement of a conductive substance with respect to a capacitive sensor formed by two parallel conductive plates, superimposed, electrically insulated from one another, and fed by a high frequency signal having a predetermined voltage, the capacitive sensor being connected to a device for detecting a current value. Also disclosed is a method for dynamic and non-contact measurement of the permittivity of a dielectric substance between a conductive part and a capacitive sensor of the above-mentioned type.

Dynamic and non-contact measurement of displacement or of permittivity by use of a capacitive sensor

A method and an apparatus for the dynamic and non-contact measurement of the distance separating the surface of a first part that may be conductive or not, from the surface of at least one second conductive part closely spaced from the first conductive part. The method resides in positioning, on the surface of the first part, at least one sensor including two conductive plates that are parallel, superimposed and electrically insulated from one another. The two plates of this at least one sensor are then fed with a same high frequency signal under the same voltage and the current generated by this high frequency signal, between the plate of the sensor which is closest to the surface of the second conductive part and this second conductive part, is measured. This measured current varying as an inverse function of the distance separating the surface of the second conductive part from the surface of the sensor which is closest to this second conductive part, it is then easy to determine the value of the distance separating the first and second conductive parts as a function of the value of the measured current. This method as well as the apparatus for carrying it out are particularly well adapted for measuring the air gap in any type of rotating machine such as an electric generator.

Apparatus for the dynamic and non-contact measurement of small distances

A non-contact measuring method and apparatus for producing a signal (34) representative of a distance (e) between facing surfaces of a first (3) and second parts (5), which are closely spaced apart such as the rotor and stator of an electric rotating machine. The method resides in positioning a sensor (7) on the surface of the first part (3). The sensor (7) includes first (9) and second (11) parallel, superimposed conductive plates electrically insulated from one another. The second plate (11) is located in between the first plate (9) and the surface of the first part (3). The first plate (9) is fed with a high frequency signal through a resistance (19). A high impedance, low input capacity, unitary gain voltage amplifier (27) is fed with the high frequency signal through the resistance (19). The second plate (11) is fed with an output signal (31) of the amplifier (27). The output signal (31) of the amplifier (27) is directly proportional to the distance (e) between the two surfaces (3, 5). The sensor (7) acts as a capacitance in a low pass RC-filtercircuit where R is the resistance (19). The sensor (7) may be adapted to determine discharges in the stator when mounted the roter.

Francois Lalonde

Papers

Alarm system and method for detecting proximity of an object to electrical power lines

Apparatus and method for evaluation a condition of a magnetic circuit of an electric machine

Dynamic and non-contact measurement of displacement or of permittivity by use of a capacitive sensor

Apparatus for the dynamic and non-contact measurement of small distances

Non-contact measuring method and apparatus for producing a signal representative of a distance between facing surfaces