SU895743A1 - Apparats for resistor braking of d.c. series excitement traction engine - Google Patents

Description

connection point for braking and joking resistors. Fig. 1 shows a circuit diagram of the proposed device; in fig. 2 is a graph of current variation versus relative duration of switching on a thyristor interrupter. The DC motor, having a winding 1 core and a winding 2 after successive excitation, forms together with a thyristor interrupt Lem 3 a sequential closed loop. The braking k and shunt 5 resistors are connected respectively in parallel to the winding 1 of the engine core and the excitation winding 2. Parallel to the excitation winding 2, a reverse diode 6 is connected. Between the point common to winding 1 kor and winding 2 excitations of the motor, and the point common to resistors and 5, current sensor 7 is turned on. The control of the thyristor interrupter 3 is carried out using the control unit 8. The output of the control unit 8 is connected to the input of the functional setpoint converter 9, the output of which is connected to the second input of the comparison element 1. The device operates as follows. During the conductive state interval of the thyristor interrupter 3, a short-circuited circuit is created: winding 1 core — excitation winding 2 — thyristor interrupter 3 and winding 1 core, therefore, the currents of the core and In excitation increase. In this case, a part of the current of the winding 1 core is branched off via the braking resistor A, and a part of the current schd is connected to the shunt resistor 5, which causes the drive field of the driver to be attenuated. During the interval of the non-conducting state of the thyristor interrupter 3, both currents are reduced, closing according to the braking resistor A (circuit winding 1 core - current sensor 7 brake resistor 4 - winding 1 core) and reverse diode 6 (circuit; winding 2 excitation - reverse diode 6 - current sensor 7 excitation winding 2). Through the current sensor 7 in the continuation of the entire period T of operation of the chopper, a current lp flows, equal to the difference of the currents i p ifl- i. At the end of the current sensor 7, a signal is generated that is proportional to the average 30 period T value of this difference Do Zc;) - g, where 3f, 0g are the average for the period T, the values of the current and excitation currents, The ratio of these currents is i6.,. Ji. The .4Й 9 V is the field attenuation coefficient and depends on the relative turn-on time of the thyristor interrupter -j and the ohmic resistances of the power circuit. In this expression, f T-l-. thyristor chopper ON time; , Box-resistance resistors of brake and shunt resistors, 5. J, is the ohmic resistance of the excitation winding. From formula (1) it follows that it is possible to write as follows: p: 41- i) D In the course of braking, as the vehicle speed decreases, the current J5 decreases. According to formula (2), with unchanged t and Tc, a decrease in vehicle speed also decreases. The thyristor interrupter control unit provides a change only upwards. When the current JP is less than the predetermined value of Jpu (setting), an increase occurs, and when Zp rc, the increase in C stops. The weakening of the excitation field of the traction motor occurs simultaneously with the change in voltage on the engine cortex. The change of f and, therefore, fi when regulating the braking force in the high-velocity region occurs in such a way that the software switching restriction of the traction motors is observed. This regulation is based on the well-known relationship that

applied to the pulse control has the following form:

(

sz

V h | b

the maximum voltage between the louvers of the engine manifold in the zone of maximum 1 reaction of the core of the main magnetic field of the main poles; the average for the interval of the conducting state of the thyristor chopper, the value of the voltage of the traction motor operating in generator mode;

coefficients depending on the design parameters of the thrust engine. of the proposed device is determined by the following offenses. QrC9

Huge device at brake process condition

(five)

e

 e

m g me 5

where 6 is the allowable value of yule. Depending on (3), the variables are bm, bd, and ft. The input element of the comparison device of the proposed device is supplied depending on the UA current difference 3 p 3 9 - 8 The expediency of using the current difference follows from the expressions for the average values of currents in the power elements of the device

wa ,,,

where is the memory mean value of current in

braking resistor. These expressions are derived from expressions (3) and (k) on the basis that the regulation of the braking process is carried out at a constant voltage between the collector laps (eNv-Swa). In expressions (6) - (9), the currents are represented in as a product of two functions | b. One of the factors

me

is an expression

who r (v)

with increasing pj, i.e. as the engine speeds decrease, it increases. According to this, the current of the engine core 2 also increases (. The excitation current J fj also

increases because in expression (7) the second factor is fv ,.

Due to the second factor (1- fi) in expression (8), the current Jp does not increase monotonically, but only

a certain value of | i (see figure 2). Then, the current Lp begins to decrease.

The regulation of the braking process is expediently carried out according to the law, which is obtained as a result of a piecewise linear approximation of the curve calculated by the formula (8), as shown in FIG. 2 by the dashed line. In the proposed device, a piecewise linear approximation is performed by a functional setpoint converter. The simplest approximation is obtained at a constant current setting in the entire adjustment interval (dash-dotted line in Fig. 2). Increasing the efficiency is achieved by increasing the number of approximation segments.

Main technical and economic

The effect of using this povicTBa is to increase the capacity of the roads. This is achieved by increasing the technical speed of movement of electric trains due to the use of automatic regulation of the braking current in the high-speed region at the maximum possible level with a permissible voltage of 6 cz between the collector lamellas in the zone of the greatest distortion of the excitation field of the core reactions. The use of resistor braking at all, including high speeds.

allows you to reduce the cost of operating brake pads and improve sanitary conditions on the platforms of stopping points as a result of the elimination of iron dust from braking the train.

Claims (1)

1. USSR author's certificate №, cl. B 60 L 7/22, 1971. Ul.1