Production of a Rotating Magnetic Field
When a three-phase offer is connected to symmetrical three-phase windings, the currents flowing within the windings manufacture a magnetic field. This magnetic field is constant in magnitude and rotates at constant speed as shown below, and is termed the synchronous speed.
With respect to Figure twenty two.1, the windings area unit described by 3 single-loop conductors, one for every part, marked RSRF, YSYF and BSBF, the S and F signifying begin and finish. In follow, every part winding includes several turns and is distributed round the stator; the single-loop approach is for clarity solely.
When the mechanical device windings area unit connected to a three-phase offer, the present flowing in every winding varies with time and is as shown in Figure twenty two.1(a). If the worth of current during a winding is positive, the idea is created that it flows from begin to finish of the winding, i.e., if it's the red part, current flows from RS to RF, i.e. aloof from the viewer in RS and towards the viewer in RF.
When the worth of current is negative, the idea is created that it flows from finish to begin, i.e. towards the viewer in Associate in Nursing ‘S’ winding Associate in Nursingd aloof from the viewer in an ‘F’ winding. At time, say t1, shown in Figure twenty two.1(a), the present flowing within the red part could be a most positive worth. At an equivalent time, t1, the currents flowing within the yellow and blue phases area unit each zero.5 times the utmost worth and area unit negative.
the present distribution within the mechanical device windings is so as shown in Figure twenty two.1(b), during which current flows aloof from the viewer, (shown as ) inRS since it's positive, however towards the viewer (shown as þ ) in YS and bachelor's degree, since these area unit negative. The ensuing magnetic field is as shown, thanks to the ‘solenoid’ action and application of the corkscrew rule.
A brief time later at time t2, the present flowing within the red part has fallen to regarding zero.87 times its most worth and is positive, the present within the yellow part is zero and also the current within the blue part is regarding zero.87 times its most worth and is negative. thence the currents and resultant magnetic field area unit as shown in Figure twenty two.1(c). At time t3, the currents within the red and yellow phases area unit zero.5 of their most worths and also the current within the blue part could be a most negative value. The currents and resultant magnetic field area unit as shown in Figure twenty two.1(d).
Similar diagrams to work twenty two.1(b), (c) and (d) will be created for all time values and these would show that the magnetic field travels through one revolution for every cycle of the provision voltage applied to the mechanical device windings. By considering the flux values instead of the present values, it's shown below that the rotating magnetic field contains a constant worth of flux.
The 3 coils shown in Figure twenty two.2(a), area unit connected in star to a three-phase offer. Let the positive directions of the fluxes created by currents flowing within the coils, be A, B and C severally. The directions of A, B and C don't alter, however their magnitudes area unit proportional to the currents flowing within the coils at any explicit time. At time t1, shown in Figure twenty two.2(b), the currents flowing within the coils are:
iB, a most positive worth, i.e., the flux is towards purpose P; American state and iC, 0.5 the utmost worth and negative, i.e., the flux is aloof from purpose P.
These currents bring about to the magnetic fluxes A, B and C, whose magnitudes and directions area unit as shown in Figure twenty two.2(c). The resultant flux is that the phasor add of A, B and C, shown as eight in Figure twenty two.2(c). At time t2, the currents flowing are:
With respect to Figure twenty two.1, the windings area unit described by 3 single-loop conductors, one for every part, marked RSRF, YSYF and BSBF, the S and F signifying begin and finish. In follow, every part winding includes several turns and is distributed round the stator; the single-loop approach is for clarity solely.
When the worth of current is negative, the idea is created that it flows from finish to begin, i.e. towards the viewer in Associate in Nursing ‘S’ winding Associate in Nursingd aloof from the viewer in an ‘F’ winding. At time, say t1, shown in Figure twenty two.1(a), the present flowing within the red part could be a most positive worth. At an equivalent time, t1, the currents flowing within the yellow and blue phases area unit each zero.5 times the utmost worth and area unit negative.
the present distribution within the mechanical device windings is so as shown in Figure twenty two.1(b), during which current flows aloof from the viewer, (shown as ) inRS since it's positive, however towards the viewer (shown as þ ) in YS and bachelor's degree, since these area unit negative. The ensuing magnetic field is as shown, thanks to the ‘solenoid’ action and application of the corkscrew rule.
Similar diagrams to work twenty two.1(b), (c) and (d) will be created for all time values and these would show that the magnetic field travels through one revolution for every cycle of the provision voltage applied to the mechanical device windings. By considering the flux values instead of the present values, it's shown below that the rotating magnetic field contains a constant worth of flux.
The 3 coils shown in Figure twenty two.2(a), area unit connected in star to a three-phase offer. Let the positive directions of the fluxes created by currents flowing within the coils, be A, B and C severally. The directions of A, B and C don't alter, however their magnitudes area unit proportional to the currents flowing within the coils at any explicit time. At time t1, shown in Figure twenty two.2(b), the currents flowing within the coils are:
iB, a most positive worth, i.e., the flux is towards purpose P; American state and iC, 0.5 the utmost worth and negative, i.e., the flux is aloof from purpose P.
These currents bring about to the magnetic fluxes A, B and C, whose magnitudes and directions area unit as shown in Figure twenty two.2(c). The resultant flux is that the phasor add of A, B and C, shown as eight in Figure twenty two.2(c). At time t2, the currents flowing are:
Production of a Rotating Magnetic Field
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April 11, 2019
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April 11, 2019
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