A new configuration of voltage-mode quadrature sinusoidal oscillator is proposed. The proposed oscillator employs two voltage differencing current conveyors (VDCCs), two resistors, and two grounded capacitors. In this design, the use of multiple/dual output terminal active building block is not required. The tuning of frequency of oscillation (FO) can be done electronically by adjusting the bias current of active device without affecting condition of oscillation (CO). The electronic tuning can be done by controlling the bias current using a digital circuit. The amplitude of two sinusoidal outputs is equal when the frequency of oscillation is tuned. This makes the sinusoidal output voltages meet good total harmonic distortions (THD). Moreover, the proposed circuit can provide the sinusoidal output current with high impedance which is connected to external load or to another circuit without the use of buffer device. To confirm that the oscillator can generate the quadrature sinusoidal output signal, the experimental results using VDCC constructed from commercially available ICs are also included. The experimental results agree well with theoretical anticipation.
This paper presents the possibility to generate the alternating current (AC) electrical power by using a linear MHD generator. The single-sided exciting winding of the generator is considered. Its structure consists of a channel, an insulator and stators. The channel type is a flat rectangular and the liquid flows along the channel as a conductor. The channel wall acted as an insulator separates the metal fluid and stator coil. The top stator winding of the generator is connected to polyphase systems. Under this condition, it can produce a magnetic field by means of time harmonics function in the same direction of the metal fluid. Energy in the channel is extracted by inductive coils at the bottom stator. An interaction between traveling wave and metal fluid is explained by finite element technique. The distributions of magnetic vector potential and magnetic field throughout channel are evidently shown in xy-plane. Power flow in an AC MHD generator is reported with magnetic Reynolds number and slip value. The optimized value of active power is suggested by small slip value as s < 0 and small magnetic Reynolds number.
This paper studies physical phenomena, performance and optimal operating point of an AC MHD generator under the slip value by using a numerical simulation. The double-side exciting winding of the generator is considered. Its structure consists of a channel, an insulator and stators. Channel type is a flat rectangular and the liquid flows along the channel as a conductor. Channel wall acted as an insulator separates metal fluid and stator coils. The top and bottom stator winding of the generator is connected to polyphase system. Under this condition, it can produce a magnetic field by means of time harmonic function in the same direction of the metal fluid. An interaction between traveling wave and metal fluid is explained by finite element method under Maxwell's equation and Ohm law. The distribution of magnetic vector potential and magnetic flux density throughout channel is evidently shown in xy-plane. Power flow in AC MHD generator is evaluated by slip value. The optimal operating point of an AC MHD generator performance is reported by active power 0.99 kW, reactive power 50 kVAR, mechanical power 1.58 kW, power dissipation 0.59 kW and electrical efficiency 62.5%.
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