Showing papers on "Power factor published in 1978"

Power supply for a high intensity discharge or fluorescent lamp

Abstract: This power supply for a high intensity gas discharge or fluorescent lamp exhibits near unity power factor with no third harmonic distortion, and facilitates highly efficient lamp operation with dimming capability. This is achieved by using an inverter to drive a resonant network that includes the lamp load. A feedback circuit adjusts the switching rate of the inverter to equal the resonant frequency of the network. Sinusoidal output voltage is achieved, together with voltage multiplication to a level sufficient to ignite the lamp and keep it lit during dimming. The inverter is driven by a switching regulator that is supplied with unfiltered, rectified ac power. A filter capacitor, connected across the regulator output, is sufficiently large so as to filter at the frequency of the rectified ac input. The regulator switching duty cycle is controlled in response to the average dc level across this filter capacitor. Lamp dimming is achieved either by adjusting the switching regulator dc output level or by varying the duty cycle of the inverter. The high power factor low distortion regulator concept may also be applied in other application where direct current power is derived from an ac line.

Transistor power losses in the class E tuned power amplifier

Abstract: The class E switching-mode tuned power amplifier offers efficiency approaching 100 percent. It is especially applicable at high frequencies because it minimizes the power dissipated during the switching transitions, even if the switching time is an appreciable fraction of the signal period. When the amplifier is properly loaded and tuned, power losses are caused primarily by active-device saturation voltage and resistance, nonzero switching time, and lead inductance. An accurate estimation of the dissipated power is presented giving more accurate circuit and thermal designs.

Practical Approaches to Supplementary Stabilizing from Accelerating Power

Abstract: Use of accelerating power to provide damping of synchronous machine oscillations through supplementary control of excitation has significant advantages. However, true accelerating power derived from Mechanical and Electrical power presents difficult measurement problems. A practical approach of deriving stabilizing action comparable to that obtainable with accelerating power is described using measurement of electrical power and frequency of a voltage synthesized from machine terminal voltage and current.

Excitation control apparatus for a generator

Abstract: A field control apparatus for a generator having a field winding comprises a terminal voltage control unit for controlling a field current of the generator in accordance with a difference between a terminal voltage signal of the generator and a reference voltage signal, which control unit has at least one of a line drop compensation function, an under-excitation limitation function, an over-excitation limitation function, a power factor regulation function, an armature winding over-current compensation function and a cross-current compensation function. The field control apparatus includes a detector as a common signal source for detecting active power and reactive power components at an output terminal of the generator and means responsive to the output of the detector for performing scalar operation in accordance with a function of the added compensation/control function described above. An output of the operating means is added to the differential signal as an added function signal to control the field current for excitation of the field winding.

Inverter circuit for energizing and dimming gas discharge lamps

Abstract: An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces a sinusoidal output voltage at about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. The ballasts consist of passive linear components. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains. The inverter circuit is provided with novel controls for gradual start-up and turn-off and is protected against load fault currents and internal fault currents. Automatic and manual resets are provided for internal fault current and load fault current, respectively. The basic inverter circuit consists of two alternately conducting controllably conductive power switching devices. Each is in parallel with a respective oppositely poled diode. The input d-c power line is connected in series with the series-connected power switching devices. A single series tuned circuit is connected in series with an output circuit element and is connected across one of the power switching devices. The amplitude of the inverter output is controlled by adjusting the phase at which the power switching devices turn on. In another embodiment, a single power switching device is used for the inverter circuit.

Variable intensity control apparatus for operating a gas discharge lamp

Abstract: A gas discharge lamp is connected in parallel with an inductor and in series with a solid state switching device and a resistor, and this combination is connected across a rectified AC voltage source. This switching device is controlled by a monostable multivibrator, the input of which is connected to the output of a comparator amplifier sensing the difference between the voltage drop across the above-mentioned resistor and a voltage which bears a predetermined relationship to the rectified AC signal of said source. This results in a high frequency operation of the lamp wherein the lamp current level is controlled or modulated in accordance with the rectified AC supply voltage, providing a high power factor lamp circuit without the normal heavy lamp ballast. In addition, a circuit is disclosed which prohibits the lamp from exhibiting a high resistance when the AC voltage is at a zero crossing point, protecting the solid state switching device and stabilizing the high frequency.

System for energizing and dimming gas discharge lamps

Abstract: An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces an output voltage at a high frequency which can be about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. The ballasts consist of passive linear components. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains.

Ballast structure for central high frequency dimming apparatus

Abstract: An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces sinusoidal output voltage at about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains. Several ballasts are disclosed, which consist principally of circuits using passive linear components. Some of the ballasts disclosed are conjugate ballasts which are those made of complex conjugate impedances which resonate with or near the input power frequency. Some ballasts disclosed are non-linear when the lamp is out in order to limit the open circuit voltage. The ballasts disclosed all have the following characteristics: (a) good power factor (above 0.8) and include at least one capacitor and one inductor; (b) are dimmable by at least 50% by a variable amplitude input having a substantially continuous wave form; (c) use only two input wires; (d) operate at a relatively high frequency (at least an order of magnitude above line frequency); (e) a good current crest factor.

D-C Power supply circuit with high power factor

Abstract: A d-c power supply is described which is energized from a relatively low frequency power source and produces a d-c output voltage with low ripple and high power factor. An inductance-capacitance circuit is connected in series with the a-c source and the a-c side of the rectifying element. A filter capacitor is connected to the d-c side of the rectifying element. The inductance-capacitance circuit resonates at a frequency of about three to six times the frequency of the input power supply. A plurality of circuits for carrying out the invention are disclosed.

Regulated switching mode power supply

Abstract: A switching mode power supply characterized by an output in the forward conversion mode and a separate output in the flyback mode whereby a device having variable power requirements in one aspect of its operation, and a stable power requirement another aspect of its operation may be powered without interference as between the two sources of power. The flyback power output is monitored for voltage regulation, regulation being achieved by a constant-off-time variable-on-time switch. The power supply likewise includes novel protective circuitry to shut it down in the event of excessive voltage or current therein.

Method and apparatus for inducting heating and melting furnaces to obtain constant power

Abstract: A method and apparatus for induction heating or melting furnaces of varying conductance, comprising controlled adjustment of the power factor angle in response to variations in load conductance to maintain constant power.

Method and apparatus for conserving energy

Abstract: A method and apparatus for regulating the luminous flux generated by a lamp with the degeneration of the voltage from a power source such as a battery. The regulating circuit maintains a constant luminous flux output from a lamp over a substantial range of voltages by switching the voltage to the lamp on and off at a preselected and controlled duty cycle. The principal advantage of this regulation is that only the minimum energy necessary to produce a required minimum luminous flux is used from the power sources irrespective of its voltage value within the operative range. The power pulses applied to the lamp are of a voltage that varies directly as the voltage variations of the power source and widths that vary as the inverse square of the voltage from the power source for maintaining a constant RMS voltage on the lamp and thereby constant light output flux. The oscillating signal generator for providing the power pulses is defined for sensing the power source output voltage variations and generates a fixed frequency signal having amplitudes varying between values directly related to the power source output voltages.

Estimation of Higher Frequency Network Equivalent Impedances by Harmonic Analysis Natural Waveforms

Abstract: A digital method of analysing harmonics in a power system has been developed which permits the equivalent network impedance to be estimated by means of the switching of capacitor banks. The method records voltage and current digitally and by data processing computes the amplitude and phase of the harmonics. By comparing results before and after the switching of a capacitor bank on one phase, the equivalent network impedance is estimated at the odd harmonics. Precision of results is acceptable in amplitude but less accurate in phase.

Unity power factor converter

Abstract: A unity power factor converter capable of effecting either inversion (dc-to-dc) or rectification (ac-to-dc), and capable of providing bilateral power control from a DC source (or load) through an AC transmission line to a DC load (or source) for power flow in either direction, is comprised of comparators for comparing the AC current i with an AC signal i ref (or its phase inversion) derived from the AC ports to generate control signals to operate a switch control circuit for high speed switching to shape the AC current waveform to a sine waveform, and synchronize it in phase and frequency with the AC voltage at the AC ports, by selectively switching the connections to a series inductor as required to increase or decrease the current i.

High efficiency wind power machine

Abstract: A high efficiency wind power machine is disclosed which is particularly well suited for large-scale, commercial conversion of wind power into electrical energy. The wind power machine of the present invention employs highly efficient wind-to-electric power conversion modules which may be interconnected to form a large-scale power converter. The individual modules employs flip-flop wind blades which travel in an oval path and are carried by traveling chains. The blades interact with the impinging wind stream at two points, thus increasing the overall efficiency of the conversion modules.

Economic Shift in Electric Power Generation with Line Flow Constraints

Abstract: This paper presents a method of finding the optimum shift in generation to eliminate overloading of lines and transformers or to maintain fixed flows on tie lines. It incorporates the concept of generalized inverse matrices, and the sensitivity matrix of power systems.

Voltage conversion system for electronic timepiece

Abstract: A voltage conversion system for an electronic timepiece having a power source, which system generates power at lower voltage level than that of the power source for operating at least one of a frequency standard, a frequency converter, a time counter circuit and a display system. The voltage conversion system comprises an oscillator circuit coupled to the power source to generate output signals, a plurality of capacitors, and a plurality of switching elements responsive to the output signals for alternately setting the capacitors in a parallel connected condition and a series connected condition, whereby an output voltage lower than that of the power source is generated at an output terminal of the system.

AC Electrical power systems with alternate sources of power

Abstract: AC electrical power system comprising an electrical alternator and a primary power source which is alternatively and automatically utilizable with an emergency power source when the primary power source fails, the primary power source being either a wind-driven impeller or a water-driven turbine which are selectively and alternatively utilized.

Control systems of alternating current motors

Abstract: In a control system of an alternating current motor energized by serially connected rectifier and inverter wherein the output DC voltage of the rectifier is controlled by a phase controller which is controlled by a phase control signal and the output frequency of the inverter is controlled by a speed reference signal there is provided a power factor detector which differentiates the phase control signal or the DC voltage and the output of the phase detector is added to the speed reference signal so as to suppress low frequency oscillations of the torque of the motor.

High frequency lighting inverter with constant power ballast

Abstract: A lighting inverter for operating an electrical discharge lamp from a direct current power source. The inverter includes a resonant feedback inverter which converts the output of the d.c. power source to an alternating current output and regulates the a.c. inverter output voltage level by varying the frequency thereof. A ballast filter is coupled to the regulated output of the resonant feedback inverter and is formed by a series circuit of a ballast inductor and a ballast capacitor. Connected across the capacitor is the discharge lamp. Appropriate circuit parameters such as ballast inductance, ballast capacitance, inverter operating frequency, and the inverter resonant frequency are selected to maintain almost unity power factor at the input to the ballast filter.

Graphical circuit analysis of two C-core type parametric power converter

Abstract: A new graphical method for analyzing the operation of two C-Core type parametric power converter is presented in this paper. The analytical results agree well with the experimental ones. The graphical method presented here is useful for designing the converter with excellent characteristics and for analyzing other power converters operating on the principle of parametric excitation.

Influence of Generator Capability Curves Representation on System Voltage and Reactive Power Control Studies

Abstract: The influence of generator capability chart representation (overexcited zone) on system voltage and reactive power control studies is examined. A load pick-up in a power system is simulated by means of a computer program and the steady--state operation in some "critical" conditions (heavy power flows and low power factors) is analyzed. Under these conditions the adoption of the simplified representation (rectangular) or of a more exact representation of the actual capability charts, may influence the search for feasible solutions to a considerable extent. Possible criteria for the optimization of system voltage and reactive power scheduling in critical conditions are also discussed on the basis of this more L exact representation.

New power convertor technique employing power transistors

Abstract: A new power convertor, using power transistors in a switching mode as the main power elements, has been introduced. This convertor is capable of conversion from a fixed 3-phase source to variable frequency, controlled output current, such that the operating frequency range is not limited by the supply frequency. The power transformers, inductors and capacitors normally associated with many existing forms of such a convertor are no longer needed. Further advantages of the new convertor are that it is capable of accepting regenerative power, operates without the need for a d.c. link and the input displacement factor is unity, regardless of the output condition.A new mode of operation, that of class ABD, has been introduced, which allows the switching rate of the power transistors to be considerably reduced for a given output. Such a technique reduces switching losses and results in a much less severe operational environment for the power transistors. It also helps to improve the power factor to a value close to unity.The present paper describes a 3-phase to single-phase convertor but the method can be used to provide a fully-regenerative 3-phase to 3-phase static converter, using only 18 power elements and producing a variable frequency, 3-phase controlled output current whose waveform is a very close approximation to a sinusoid.

A Novel Method of Direct Digital Integral-Cycle Power Control

Abstract: A circuit, based on pulse-rate techniques, is described which provides direct digital integral half-cycle thyristor (or triac) control of ac power. It is shown, and proved experimentally, that the method provides the optimum time distribution of the conducting half-cycles. This results in minimal temperature ripple when, for example, the circuit is used to control heater power. The circuit is simple and inexpensive and uses only standard components.

Power angle relay to measure and respond to the power angle of a synchronous generator

Abstract: A power angle relay to measure the power angle of a synchronous alternator. The power angle relay receives a reference voltage signal corresponding to a fixed point on a reference voltage waveform (usually a zero crossing) from some point in the power system to which the alternator is normally synchronized and an electric signal representative of the angular position of the shaft of the synchronous alternator and is operable to combine the two to provide an indication representative of the power angle between the direct axis of the synchronous alternator and said fixed point.

Combination oven fully utilizing the capability of a limited power source

Abstract: A cooking oven having both microwave and electrical resistance heating means and which fully utilize the capabilities of a limited-capability power source to achieve the shortest possible cooking time. The oven has a microwave energy generating system which requires less than all of the available current when operated at its full rated power level, and an electrical resistance heating element which requires substantially all of the available current when operated at its full rated power level. The oven also has a means for at least successively energizing the microwave energy generating system and the electrical resistance heating element at their respective full rated power levels. Additionally, there is a means for energizing the electrical resistance heating element from the power source at a reduced power level when the microwave energy generating system is energized at its full rated power level. The reduced power level is selected such that the total of the currents required to operate the microwave energy generating system at its full rated power level and to operate the electrical resistance heating element at the reduced power level is no greater than and, preferably substantially equal to, the power source capability.

Power and Current Pulsations of an Induction Motor Connected to a Reciprocating Compressor

Abstract: The influence of a periodic pulsating torque variation on a polyphase induction motor is described. A calculation method is outlined to predict the current, power, and torque pulsation along with the effect on power factor, slip, and efficiency. The calculation method is compared with tests and a digital solution of the differential motor equations.

Evaluation of Control Schemes for Thyristor-Controlled DC Motors

Abstract: Phase-angle control (PAC) is commonly used in the solid-state control of dc motor drives. This paper investigates other control schemes, such as symmetrical-angle control (SAC), extinction-angle control (EAC), current-limit control (CLC), and time-ratio control (TRC). The drive system with the control schemes is simulated on a digital computer and an efficient time-saving method is used for computation. The performance characteristics, such as torque speed, input power factor, fundamental power factor, harmonic content, and peak motor current are obtained and compared for the different control schemes. Each control scheme has certain advantages over the others. The control schemes are implemented on an experimental setup to demonstrate the basic principles of operation.

Circuit control to limit power drain of auxiliary power supply in UPS system

Abstract: An uninterruptible power supply includes a digital control circuit to control the transfer of power from a primary and a secondary power source to a load circuit to be energized. The digital control circuit controls through digital techniques the relative phase angles of a primary power signal, a secondary power signal, and a load signal to advantageously minimize the power drain on an idling secondary power source when the primary power source is active and to minimize transients in the load signal when converting from one power source to another.

Closed loop solar array-ion thruster system with power control circuitry

Abstract: A solar array-ion thruster system including a power control circuit which provides for use of the thruster itself in operating the solar array at the maximum power point. The power control circuit is connected between the solar array and the ion thruster and receives voltage and current signals from the former. The control circuit multiplies the voltage and current signals together to produce a power signal which is differentiated with respect to time. The differentiator output is detected by a zero crossing detector and, after suitable shaping, the detector output is phase compared with a clock in a phase demodulator. An integrator receives no output from the phase demodulator when the operating point is at the maximum power point but is driven toward the maximum power point for non-optimum operation. A ramp generator provides minor variations in the beam current reference signal produced by the integrator in order to obtain the first derivative of power.