摘要:
According to an aspect of the invention, a motor drive circuit includes a first energy storage device configured to supply electrical energy, a bi-directional DC-to-DC voltage converter coupled to the first energy storage device, a voltage inverter coupled to the bi-directional DC-to-DC voltage converter, and an input device configured to receive electrical energy from an external energy source. The motor drive circuit further includes a coupling system coupled to the input device, to the first energy storage device, and to the bi-directional DC-to-DC voltage converter. The coupling system has a first configuration configured to transfer electrical energy to the first energy storage device via the bi-directional DC-to-DC voltage converter, and has a second configuration configured to transfer electrical energy from the first energy storage device to the voltage inverter via the bi-directional DC-to-DC voltage converter.
摘要:
Power is transferred from a stationary power supply to a rotational gantry in a computer tomography (CT) system through a rotary transformer arranged in a ring configuration with an inner diameter that is sufficiently large to receive a patient. The rotary transformer has a toroidal rotor core and a toroidal stator core arranged either concentrically with an air gap extending radially therebetween or side-by-side with an air gap extending axially therebetween. A resonant inverter provides ac power to the rotary transformer which, in turn, drives a high-voltage tank circuit coupled to a x-ray tube, the tank circuit and x-ray tube being mounted on a rotational gantry. Advantageously, this is a contactless power transfer system which eliminates conventional brush and slip ring arrangements and moreover avoids the need for mounting the inverter to rotate with the CT gantry.
摘要:
A power supply system for thrusters (e.g., arcjet thrusters) in a spacecraft system comprises lightweight, redundant power supplies that share the power distribution function to the thrusters. Each power supply comprises a plurality of parallel-connected power supply subunits of which the combined power output capability exceeds the required maximum power demand by at least one subunit capacity for each arcjet thruster in the system. Each power supply subunit comprises a lightweight, high-frequency, soft-switching power supply. For arcjet systems comprising arcjet thrusters that do not operate simultaneously, relays are employed to switch between thrusters.
摘要:
A power supply includes a dc-to-dc converter with an integral boost power supply for maintaining the effective converter input voltage within a predetermined steady-state range, even if the input voltage to the power supply exhibits substantial voltage transients. In one preferred embodiment, the boost power supply comprises a boost transformer and a rectifier, and the converter comprises two parallel-coupled resonant converter modules, each including either a half-bridge or full-bridge connection of switching devices and a resonant circuit. The primary winding of the boost transformer is coupled between the junctions joining the switching devices of the resonant converter bridges. When the power supply input voltage is outside the steady-state voltage range, the boost power supply is activated by phase shift control of the voltage across the primary winding of the boost transformer.
摘要:
A control circuit for insuring super-resonant operation of a DC-to-AC resonant converter, having a resonance circuit with a resonant frequency F.sub.r, in which a circulating current i.sub.r flows between a first node A, alternatingly connected between an input potential and a primary common potential at an operating frequency F, and a second node B, includes: a subcircuit for generating a first signal representative of the phase of the circulating current i.sub.r ; another subcircuit for generating a second signal representative of the phase of a potential V.sub.AB between the first and second nodes; and a comparator which compares the first and second signals to increase the operating frequency F if the phase of the circulating current i.sub.r leads the phase of the node-to-node potential V.sub.AB. The reasonance circuit can be a series, parallel or series-parallel resonant arrangement, typically driven by a pair of alternatingly-conductive semiconductor switching devices, themselves driven by a voltage-controlled oscillator (VCO). In one embodiment, the VCO frequency is increased whenever a current zero crossing occurs before the end of a VCO waveform half-cycle.
摘要:
In a converter for a switched reluctance motor, a dump capacitor receives freewheeling current from each phase and resupplies the charge to the dc supply. In this manner, residual magnetic energy is recovered and phase current quickly reduced while the converter requires only one main switching device and one freewheeling device per phase and the converter allows a unipolar source to be used.
摘要:
A high gain latching Darlington transistor comprises a gate turn-off thyristor and a load transistor coupled in Darlington configuration. Circuit means including a diode are coupled to the gate turn-off thyristor and the transistor to provide a low loss path for load transistor current which reverse biases the gate-cathode junction of the thyristor at thyristor turn-off to prevent premature device conduction. The latching Darlington transistor configured in this manner thus operates as a conventional gate turn-off thyristor, capable of being pulsed into and out of conduction, but yet exhibits improved dv/dt capability and increased turn-off gain, typically between 10 and 100 times the turn-off gain of the individual gate turn-off thyristor.
摘要:
A parallel resonant induction cooking surface unit comprises a voltage fed inverter which drives a load circuit, comprised of a main induction drive coil, a tuning capacitor coupled in parallel with the main induction drive coil, and an inductor coupled in series with the main induction drive coil, with a square wave voltage, causing the main induction drive coil to generate a time variant magnetic field resulting in eddy currents being induced in the surface of a metallic, food-containing utensil positioned adjacent to the main induction drive coil, and hence, utensil heating. By tuning the load circuit to resonance at or near the square wave frequency, reactive currents therein are minimized, resulting in improved power factor. Moreover, resultant main induction drive coil voltage and current are nearly sinusoidal, thereby achieving reduced electromagnetic interference radiation at frequencies greater than the square wave frequency.
摘要:
Method and apparatus for evenly distributing the switching duty among power transistors in a full bridge inverter controlled by current band PWM, by switching first the top half of the bridge and then the lower half of the bridge to shape the output current waveform.
摘要:
A single transistor DC--DC battery charger provides ohmic isolation with a multiple winding high frequency transformer. The transistor's duty cycle is determined from an isolated voltage proportional to battery voltage obtained from a signal winding of the transformer when the transistor is off.