Switched Reluctance Drives Limited

Chloride Group Limited

Power Electronic Measurements Limited

Chloride Group Public Limited Company

Tasc Drives Limited

William Frederick Ray

Rex Mountford Davis

John M Stephenson

Christopher Rene Hewson

Joanne Marie Aberdeen

A temperature compensated current measurement device comprises a Rogowski coil having a terminating impedance arranged to adjust the attenuation of the coil to balance changes in coil sensitivity so that the output voltage indicative of measured current remains substantially unchanged, the terminating impedance having different values above and below a threshold frequency.

Temperature compensated current measurement

A voltage to current converter is provided for use with a current measuring device, said current measuring device being operable to provide an output voltage which is an analog of a current to be measured. The converter is arranged to provide an output current which is an analog of the current to be measured. The converter comprises an electronic controller, a switching amplifier and means for measuring the output current as an analog voltage and providing a measure of said analog voltage to the electronic controller.

Apparatus for current measurement

A current measuring device comprising a Rogowski coil ( ). Connected across ends of the coil ( ) is a passive integrator in two parts ( ), the parts being connected by a coaxial cable ( ). Connected to the output of the passive integrator ( ), is an electronic integrator ( ). At low frequencies the passive integrator ( ) has a substantially constant gain and the electronic integrator ( ) integrates the signal from the coil ( ). At high frequencies, the electronic integrator ( ) has substantially constant gain and the passive integrator ( ) integrates the signal from the coil ( ). In order to reduce high frequency voltage oscillations, the Rogowski coil ( ) is terminated with a coil damping resistor that has a value that is approximately the same as a characteristic impedance of the coil.

Current measuring device

A control system is provided for use with an actuator in a load-positioning assembly. The actuator and its load are quickly and accurately driven to a target position using dual control modes. When the distance from the target position is large, a speed control mode is used. In this mode, the actuator is operated according to a speed demand profile which is a function of a programmable maximum speed and the distance remaining to the target position. When the distance to the target position is small, a stepping mode is selected for final positioning of the actuator and its load.

Dual mode position control system with speed profiling

A control system for and method of controlling a switched reluctance generator to maintain stable control of the generator in the continuous current mode. This is achieved by sensing the load on the generator, the speed of the rotor and the position of the rotor with respect to each phase winding in order to derive switching command signals to maintain the volt-seconds applied to the winding in each phase period so as to inhibit progressive flux growth in the phase windings by actuation of the controller switches.

Control of switched reluctance machines

A control system for and method for controlling a switched reluctance generator to maintain stable control of the generator in the continuous current mode. This is achieved by sensing the load on the generator, the speed of the rotor and the position of the rotor with respect to each phase winding in order to derive switching command signals to maintain the volt-seconds applied to the winding in each phase period so as to inhibit progressive flux growth in the phase windings by actuation of the controller switches.

A sensorless rotor position measurement system comprises a digital processor (6) which receives signals from current and flux sensors (7, 8) of the current and flux associated with a phase winding of the machine. The measurement of the current and flux is enabled at a predicted reference rotor position. The measurements are compared with stored values of current and flux and an error between the actual and the predicted reference position calculated. The calculated rotor position can then be used to predict the instant the rotor will reach the next reference position.

Sensorless rotor position measurement in electric machines

Power conversion circuit

Electric power converter circuit

Variable reluctance motor systems

Variable reluctance electric motor systems

In a variable reluctance electric drive system motor the fractions of a cycle during which the winding inductance of a phase increases with movement in either direction are such that the motor is self starting in either direction. The timing of the power converter in relation to the cycle of inductance is such that the current increases from its minimum value to substantially its maximum value while the winding inductance is substantially at its minimum value and thereafter substantially decreases before the power converter disconnects the winding from the supply. This can be achieved by making the switch-on and commutation of current occur at predetermined positions so related to the variation of inductance that the peak current ip at maximum power and maximum speed, is greater than I, where I=E/(R+dL/dt), E is the supply voltage, R the winding resistance and dL/dt is the maximum rate of increase of inductance before the commutation point.

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Attenborough, United Kingdom

William Frederick Ray