Magnetic saturation

Figure 28.28 A typical magnetic saturation (B-H) curve for CRGO sheets...

The power convertor must provide the AC motor with low-harmonic voltage waveform and simultaneously allow the amplitude to be adjusted. This avoids magnetic saturation of the motor as the frequency is adjusted. For constant torque, from maximum speed to base speed, the voltage is adjusted proportional to frequency. Above base speed, the motor is usually operated at constant horsepower. In this region the voltage is held constant and the flux density declines. Also, the convei tor must limit the starting current, ensure operation at favorable slip, and provide a path fitr reverse power flow during motor slowdown. 

The British Gas version uses magnetic saturation, and can identify corrosion on both internal and external pipe surfaces. The specification for seamless pipe is ... 

The calculated energy of interaction of an atomic moment and the Weiss field (0.26 uncoupled conduction electrons per atom) for magnetic saturation is 0.135 ev, or 3070 cal. mole-1. According to the Weiss theory the Curie temperature is equal to this energy of interaction divided by 3k, where k is Boltzmann s constant. The effect of spatial quantization of the atomic moment, with spin quantum number S, is to introduce the factor (S + 1)/S that is, the Curie temperature is equal to nt S + l)/3Sk. For iron, with 5 = 1, the predicted value for the Curie constant is 1350°K, in rough agreement with the experimental value, 1043°K. 

The top magnetic pole, 2 to 4 /rm thick, and overpass lead, which provides electrical connection to the central tap of the coils are now deposited and patterned (as in step 2). The back regions of the magnetic poles are, as a rule, made thicker than the p>ole tips, to achieve high head efficiency and avoid magnetic saturation. 

Both possible valence states contribute in the ratio 78 22, giving iron the necessary magnetic saturation moment of 2.22 magnetons. This concept leads to a valency of 5.78. 

Recently, the discovery of short range ferromagnetic interactions (SRFM) (Weiss temperature, 0 IK from l/% vs T, magnetization saturation curves corresponding to S = 2, rather than S = 1/2) in crystals of 1(2) was reported(7, ). 

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