Abstract:
A controller for an electromechanical transducer is provided. The controller comprises driving means operable to actuate a mechanical output of the transducer; impedance cancelling means operable to at least partially cancel an electrical impedance of the transducer; and linearising means between an input of the controller and the driving means. The linearising means are operable to generate an output signal by modifying an input signal of the linearising means to compensate for nonlinear behaviour of the transducer. The linearising means are operable to receive one or more state signals indicative of one or more state variables of the transducer, the one or more state signals comprising a velocity signal indicative of a velocity of the mechanical output of the transducer.
Abstract:
A switching circuit for a reluctance machine includes one or more half-bridge converter modules including serially connected switches connected between power rails +V.sub.dc and -V.sub.dc. A pair of capacitors are also connected between the power rails, and the phase winding of the machine is connected at one end between transistors and at the other end between the capacitors. The switches act as separate power circuits, alternately conducting to excite the phase winding either during alternate phase conduction periods or during alternate groups of phase periods. The half-bridge modules are commercially readily available as cost-effective preassembled items.
Abstract:
A switched reluctance machine run as a servo-motor has its torque ripple reduced by shaping the chopping current by which the rotor is rotated relative to the stator. The shaping includes reducing the rate of change of torque with respect to time such that the magnitude of the torque ripple is reduced and therefore more easily rejected by the control function of the machine controller.
Abstract:
A controller for an electromechanical transducer is provided. The controller comprises driving means operable to actuate a mechanical output of the transducer; impedance cancelling means operable to at least partially cancel an electrical impedance of the transducer; and linearising means between an input of the controller and the driving means. The linearising means are operable to generate an output signal by modifying an input signal of the linearising means to compensate for nonlinear behaviour of the transducer. The linearising means are operable to receive one or more state signals indicative of one or more state variables of the transducer, the one or more state signals comprising a velocity signal indicative of a velocity of the mechanical output of the transducer.
Abstract:
A current controller for a switched reluctance machine is disclosed. The current controller controls the switching frequency of the power devices that control the energization of the phase windings of the machine and the peak magnitude of the phase current in response to a single pulse width modulated signal. Also disclosed is a method and circuit for implementing slope compensation in a current controller for a switched reluctance machine where the magnitude of the slope compensation is proportional to the voltage of the power supply from which the phase windings are energized.
Abstract:
A switched reluctance machine controller derives an error signal from the difference between a current reference and the phase winding current. The error signal is applied to a pair of hysteresis circuits which define adjacent hysteresis bands above and below the reference current. The magnitude of the hysteresis bands may vary as a function of the current reference. The outputs of the hysteresis circuits are received by control logic which permits current to be applied to the phase winding when the current is below the hysteresis bands, removes current from the phase winding when the current is above the hysteresis bands and allows the phase winding current to freewheel when the current is between the upper and lower hysteresis limits. The power device used for freewheeling alternates between an upper power device and a lower power device.
Abstract:
A brushless electrical machine has at least one phase winding which produces magnetic flux in the machine. A controller controls the flux in the machine with reference to a demanded flux and a stabilisation signal which, in combination, enable the controller to operate in a stable manner in the presence of disturbances in the inputs or parameters of the controller. The controller is able to operate with either a hardware rotor position detector or with a sensorless position algorithm.
Abstract:
A brushless electrical machine has at least one phase winding which produces magnetic flux in the machine. A controller controls the flux in the machine with reference to a demanded flux and a stabilisation signal which, in combination, enable the controller to operate in a stable manner in the presence of disturbances in the inputs or parameters of the controller. The controller is able to operate with either a hardware rotor position detector or with a sensorless position algorithm.
Abstract:
A power train controller can operate in either motoring or braking modes. Its prime mover accepts a limited proportion of braking power and the remainder of the braking power is dissipated in an energy dump. A control system is arranged to maintain the voltage bus of the power train at a constant value throughout both modes.
Abstract:
A current transducer includes a current transformer in which the conductor carrying the current to be monitored constitutes the primary. The transformer secondary is wound on a toroidal core. The transformer is operated below its cut-off frequency such that the output from the secondary is proportional to the differential of the current in the primary. The secondary output is integrated by an integrator to provide a measure of current in the primary and the integrator is initialized at predetermined intervals. A current measuring device for an electric machine, for example a reluctance machine, includes at least one of the current transducers.