This paper uses the method of complex time variable to deduce the tran-sfer functions of induction motors in the type of current control slid-frequency control system and the system controled by the secondary exciting current constant under general conditions.

The results of the experiments show that the system, compared with the general PID controller, is more stable and can keep the current constant in the welding process, and then guarantees the quality of the welding.

In view of the influence of charging procedure on the service life of charger,the paper designs an intelligent battery charger based on MC68HC08,develops hardware circuit and software of intelligent controller,as well as puts forward the three-phase charging procedure of Constant Current,Constant Voltage and Tiny-Steam Charging,thus the intelligent control being realized.

Besides,the control system also utilizes such quality monitoring techniques as constant current,constant voltage and step rising current etc,and has comprehensive functions of half wave welding,whole wave welding etc.

Based on analyzing the high-speed welding process, this paper introduced various electrical current waveform control methods such as constant current, constant voltage, big constant current and small constant current. And it also introduced their work process respectively.

The paper proposes the basic structure and principle of the main circuit of IGBT AC TIG welder with douple inverted square wave. The primary inversion is designed as both negative current feedback and threshold sythetic control system to keep current constant. The secondary inversion is used for controlling the arc starting.

This article presents an analysis of voltage and current control modes of DC/DC converter and proposes a multi-purpose controller working in constant voltage,constant current,constant power states alterable.

The system adopting the single-chip microcomputer of intel80C196KC as the core tool and fuzzy logic as the adjusting way can compensate for the all kinds of influences on the welding current and make the current constant in the welding process, thus it can guarantee the quality of the welding.

According to the analysis of the starting characteristic of induction motor and the comparison on PID control and fuzzy control, this paper presents a design method of induction motor soft starting based on fuzzy control. Through measuring input current, and processing fuzzy inference, the fuzzy controller can change the control angle of thyristor, keep the starting current constant and increase the terminal voltage, therefore get better control results.

It includes the following aspects: Using the compact circuits and SCM AT89S52, finishing the design of high-power direct current constant power supply whose protected current could be constant adjusted, connecting the character that hardware circuits respond quickly with the advantage that software's protection is steady, and expanding functions of traditional constant power supply.

At pH 3.0, the value of limiting diffusion-current constant (K) was 8.42?±?0.23 (n?=?7).

In BRb of pH?=?4, the diffusion-current constant was 6.45?±?0.07?μA?·?mM-1.

Circuit arrangement to keep a stimulating current constant

An addition of the crown ether shifts the reduction potential of In(III) towards the negative side, its current remaining unchanged, while that of Cd(II) almost did not change, also leaving the wave current constant.

Within the current constant Q layer, we use Gabor spectral analysis on the signals to pick time-variant gain-constrained frequencies and then deduce the corresponding gain-constrained amplitudes to stabilize the inverse Q-filtering algorithm.

The polarographic wave due to the hydrolysis of zirconyl chloride in 0.1 M KC1, N(CH3)4Br or KKO3 solution has been found to be proportional to the concentration of zirconyl chloride and may be used as the basis for its quantitative determination.It has been demonstrated by pH measurement and conductometric titration that the hydrolysis proceeds quantitatively as follows:ZrOCl3+H2O = ZrO(OH)Cl+HClThe diffusion current constant cf the hydrolytic wave is smaller than the ordinary hydrogen wave because the...

The polarographic wave due to the hydrolysis of zirconyl chloride in 0.1 M KC1, N(CH3)4Br or KKO3 solution has been found to be proportional to the concentration of zirconyl chloride and may be used as the basis for its quantitative determination.It has been demonstrated by pH measurement and conductometric titration that the hydrolysis proceeds quantitatively as follows:ZrOCl3+H2O = ZrO(OH)Cl+HClThe diffusion current constant cf the hydrolytic wave is smaller than the ordinary hydrogen wave because the presence of ZrOCl2 increases the viscosity of the solution and hence decreases the diffusion coefficient of the hydronium ion.

Theories of the "dead-stop" end-point method of titration of Foulk andBawden have been studied recently by Delahay, Kies, Duyckaerts,Gauguin and Charlot, and Bradbury, but no conclusive remarks have beenobtained by these authors as to the choice of optimum experimental conditionssuch as the applied voltage, the initial concentration of the solution to betitrated, the temperature, the electrode area, the stirring rate, the resistancein the circuit and the sensitivity of the galvanometer. This situation hashandicapped...

Theories of the "dead-stop" end-point method of titration of Foulk andBawden have been studied recently by Delahay, Kies, Duyckaerts,Gauguin and Charlot, and Bradbury, but no conclusive remarks have beenobtained by these authors as to the choice of optimum experimental conditionssuch as the applied voltage, the initial concentration of the solution to betitrated, the temperature, the electrode area, the stirring rate, the resistancein the circuit and the sensitivity of the galvanometer. This situation hashandicapped the wide applicability of this method, although it yields accurateresults and requires only inexpensive equipment. In the above mentioned theories, it is generally assumed that the iR dropin the circuit may be neglected i. e., the concentration overpotential E_πis equalto the applied voltage E and will not change in the course of the titration.But it is found experimentally that the magnitude of the resistance in thecircuit will greatly effect the shape of the titration curve and the sharpness ofthe end point. In fact, if we want to increase the sensitivity of the method(i. e., to titrate very dilute solutions), it is necessary to insert a high resistance(as high as a mega ohm) in the circuit in order to have a sharp end point In view of the above considerations we have derived the equations, g=i/i_0 =xSE~(-1)(Y_B-1)/(Y_B+1), 0≤x<0.5 (1a) g=0.5SE~(-1)(Y~(1/2)-1)/(Y~(1/2)+1) x=0.5 (1b) g=(1-x)SE~(-1)(Y_A-1)/(Y_A+1), 0.51 (1e)for the intensity of current i as a function of the "fraction x being titrated"(at the end point, x=1) during the titration of A with D as shown by thefollowing reaction: A+D=B+C (2)where A/B and C/D are two reversible redox pairs. In these equations, g=the ratio of the current i at any given stage during the titrationto that i_0 which would be obtained if the concentration overpotential E_π were zero. This latter quantity is equal to the applied voltage E divided by thetotal resistance R in the circuit, i. e., i_0=E/R. S="the dead-stop titration constant" which determines the shape ofthe titration curve and is equal to the product of three quantities: 1) thediffusion current constant of A, k_A, 2) the initial concentration of A, C_0, 3)the total resistance, R; i. e., S = k_AC_0R. K=the equilibrium constant of the reaction (2). α=the ratio of the diffusion current constant of D to that of A, i. e.,α=k_D/k_A. Y_A=the ratio of the concentration of A at the anode, (A)_a, to that atthe cathode, (A)_c, i. e., Y_A = (A)_a/(A)_c; similarly, Y_B=(B)_c/(B)_a; Y_c= (C)_a/(C)_c; Y_D =(D)_c/(D)_a. Y=Y_AY_B=Y_CY_D=exp{(1-g)nFE/RT}, where n, R, T have theusual meaning as used in electrochemistry. At any given stage of titration, x and Y are known, then Y_j's (j=A, B,C, D) may be calculated as follows: Y_j=Q(Y-1)+(Q~2(Y-1)~2+Y)~(1/2) (3)In the above expression, when j=A, Q=x-0.5; when j=B, Q=0.5-x;when j=C, Q=0.5-1/x; when j=D, Q=1/x-0.5. Since g is a measurable quantity, Y is a function of g and E, so thatequation (1b) provides a convenient means to evaluate S and hence k_A. Differentiating (1c) with respect to x, we obtain (dg/dx)_(x→1)=-SE~(-1)(Y-1)/(Y+1) (4)this is the expression for the steepness of the current change near the endpoint. The theoretical titration curves and their slopes near the end point as cal-culated with the aid of the equations (1), (3) and (4) were plotted in Fig. 2 (p. 8),where the applied voltage being fixed at 59 mv but the dead-stop titrationconstant S has been varied tenthousand-fold. From this figure we may drawthe following conclusions: (1) At the given applied voltage, the larger the S the steeper the titra-tion curve. Steeper curve will give more sharp end point, but it is not ad-vantageous if the curve is too steep, since there will be no warning whenapproaching the end point and a drop of the reagent may be sufficient to causea jump from the left to the right branch of the titration curve over thecurrent minimum. The most suitable value of S is in the order of magnitudeof ten. (2) For the titration of Ce (IV) with Fe (II) at room temperature usingtwo platinum foil electrodes of area of about 0.8 square centimeters, we foundk_A is in the order of magnitude of 0.1. Since S=k_AC_0R the product of C_0and R should be in the order of magnitude of 10~2. If C_0=10~(-3)M then a resistanceof about 10~5 ohms should be inserted. (3) Since k_A=nFAD_A/δ, the factors which determine k_A are: the elec-trode area A, the diffusion coeficient D_A and the effective thickness of the diffusion layer δ, these latter quantities are effected by the temperature andthe viscosity of the solution, the rate of stirring, etc. Fig. 3 is a similar plot, but in this case S is fixed at 0.59, while E variesfrom 5.9 to 590 mv. From this figure we see that the slopes of the titrationcurves for E=295 and 590 mv are smaller than those for E=118, 59 and 5.9mv, so that an applied voltage over several hundreds mv is usually disadvan-tageous in the dead-stop titration. On the other hand, too small an appliedvoltage is also inconvenient because then a much more sensitive galvanometermust be used and the current readings will sometimes be erratic due to sometemporary polarization effects. The experimental test of the above theory will be reported in the nextcommunication.

It was found that the polarographic behavior of cadmium ion in 0.5 M H_2SO_4 solution containing 0.01% gelatin is unsatisfactory because the diffusion current does not attain a perfect constant value but continues to increase gradually up to the potential of hydrogen discharge.The polarographic behavior of cadmium ion in 0.5 M H_2SO_4 solution without gelatin is studied in this work. It is found that the polarographic behavior of cadmium ion in 0.5 M H_2SO_4 is excellent.The current-potential curves of cadmium...

It was found that the polarographic behavior of cadmium ion in 0.5 M H_2SO_4 solution containing 0.01% gelatin is unsatisfactory because the diffusion current does not attain a perfect constant value but continues to increase gradually up to the potential of hydrogen discharge.The polarographic behavior of cadmium ion in 0.5 M H_2SO_4 solution without gelatin is studied in this work. It is found that the polarographic behavior of cadmium ion in 0.5 M H_2SO_4 is excellent.The current-potential curves of cadmium ion in 0.5 M H_2SO_4 solutions in which the concentration of cadmium varies from 0.050mM to 20.0mM are determined and the well-defined polarographio waves with limiting diffusion current and easily determined half-wave potential are obtained. The limiting diffusion current (wave height) of cadmium ion in 0.5M H_2SO_4 is proportional to its concentration. The half-wave potential of cadmium ion only varies slightly in the range of-1.011～-1.047 V (vs. 0.5 M mercurous sulfate electrode) as the concentration of cadmium ion varies from 0.05mM to 20.0mM. Therefore, cadmium can be determined quantitatively and qualitatively by polarographic method in H_2SO_4 solution.The following polarographic data of cadmium ion in 0.5M H_2SO_4 solution are obtained: the diffusion current constant i_d/cm~(2/3) t~(/6)=3.97μA/mM?mg~(2/3)·s~(1/2) the half-wave potential E_(1/2)=-1.011 V(vs. 0.5M mercurous sulfate electrode) or E_(1/2)=-0.559 V (vs. SCE), and the number of electron transferred in the electrode reaction n=2.