SU1394384A1 - Method of controlling d.c. thyristor drive of drawworks - Google Patents

Abstract

The invention relates to electrical engineering and can be used in electric drives with dual-zone regulation / development. The aim of the invention is to eliminate self-oscillations during the descent of the load. In the device, which implements this method, the sign of the mismatch between the given and actual speeds is additionally determined with the help of a sensitive element. The mass of the load is measured using a mass sensor 17. When the load mass is in the range specified by the indicator 18, the actual speed exceeds the set speed and the load descent mode is in effect, the logic element 19 acts on the switch 13. The output of the control unit 10 is the EMF disconnected from the input of the block 11 and connected to the output of the block 14 to form a control effects on the excitation current control loop. In this control method, the required rate of increase of the braking moment is provided when switching to the regenerative braking mode. 4 il. eaten

Description

sixteen

with so

with

00 4;

The invention relates to electrical engineering, namely to thyristor DC drives with two-zone speed control.

The purpose of the invention is to exclude self-oscillations during the descent of the load.

FIG. 1 shows a functional diagram of the device that implements the method; in fig. 2 is a functional block diagram of a current setting unit J in FIG. 3 and 4 are oscillograms of a transient process for controlling known and proposed electric drives.

16 and a level indicator .18 are connected respectively to the first, second and third inputs of the AND 19 logic element, the output of which is connected to the control of the inputs of the controlled switch 13 and the force control unit 12.

The excitation current setting unit 14 (Fig. 2) consists of the reference voltage source 20, the division 21 unit, the input of which is divisible is connected to the output of the reference voltage source 20, and the divider input is from the output

The electric drive contains an electric motor - a 5 set speed homer;

25

galer 1, the root circuit of which is connected to an irreversible thyristor converter 2, controlled by control unit 3, to the input of which speed controller 4 is connected, the output of which is also connected to one of the inputs of comparison unit 5, the second input of which is connected to the output of speed sensor 6 and the output of the comparator unit 5 is connected to the input of the braking control unit 7, the first output of which is connected to the control input of the control unit 3. The motor excitation winding 8 is powered by a reversing converter 9, in 30 the control circuit of which is connected to the EMF control unit 10, the excitation current control unit 11, the control input of which is connected to the second output of the braking control unit 7 and the exciter voltage forcing control unit 12. In addition, the device contains a control switch 13, a block 14 for setting the excitation current, first and second sign-sensitive relay elements 15 and 16, a mass sensor 17, a level indicator 18 and an AND 19 logic element. At the same time, the first input of the controlled switch 13 is connected to the output the EMF unit 10, the second input of the controlled switch 13 is connected to the output of the excitation current task unit 14, and the output of the controlled switch 13 is connected to the input of the excitation current control unit 11, the output of the comparison unit 5 is connected to the input of the sensitivity sensor Nogo relay element 15, the output rate of dt sensor 6 - to the input of the sign-sensitive relay element 16, and the output of the sensor masses 17 - 18 to the input of the indicator layer. The outputs of the sensing relay elements 15 and

This divider 21 is connected to the input of the functional converter 22, the output of which is the output of the drive current command unit.

The way to control the thyristor electric drive of the drawworks is to set the speed of the electric drive, measure its actual value, compare the set and actual speed, determine the sign of their mismatch, and if the actual speed is exceeded, set the braking command the weight of the load is detected, the mode of load lowering is detected and, when the weight of the load is in a given range, in the mode of lowering the load simultaneously with the command to brake, reduce the coefficient ient forcing excitation and alter the current task, the excitation is inversely proportional to a predetermined speed.

The drive works as follows.

Using a speed setting device 4, set the speed setpoint to the power descent, measure the speed 6 of the actual speed of the motor 1, measure the speed of rotation of the electric motor 1, compare the set and actual speed of the electric drive and compare the actual speed of the set value brake control. In addition, the sign of the mismatch between the desired and actual speeds of the electric drive is determined with the help of the sensitive element 15, the sign of speed, the corresponding descent of the load, using the sensitive sensing relay element 16, as well as the weight of the load using the mass sensor 17. With

35

40

SO

55

0

five

0

This divider 21 is connected to the input of the functional converter 22, the output of which is the output of the drive current command unit.

The way to control the thyristor electric drive of the drawworks is to set the speed of the electric drive, measure its actual value, compare the set and actual speed, determine the sign of their mismatch, and if the actual speed is exceeded, set the braking command the weight of the load is detected, the mode of load lowering is detected and, when the weight of the load is in a given range, in the mode of lowering the load simultaneously with the command to brake, reduce the coefficient ient forcing excitation and alter the current task, the excitation is inversely proportional to a predetermined speed.

The drive works as follows.

Using the speed setting device 4, set the speed setpoint to the power descent, measure the speed sensor 6 with the actual speed 5 of the motor 1, compare the set and actual speeds of the electric drive in comparison unit 5 and, if the actual speed exceeds the set value, issue a braking command using block 7 brake control. In addition, the sign of the mismatch between the target and actual speeds of the electric drive is determined by means of the sensing element 15, the sign of the speed, the corresponding descent of the load, by means of the sensitive sensing relay element 16, and the weight of the load by means of the mass sensor 17. With

five

0

O

five

the following conditions coincide: the weight of the load is in the range specified by the indicator 18, the actual speed is set by what is determined by the comparison unit 5 and the sign-sensitive relay element 15, and the presence of the load descent mode, which is determined by the sign-sensitive relay element 16 - the logic element AND 19 acts on the control input of the controllable switch 13, thereby disconnecting the input of the EMF control unit 10. From the input of the excitation current control unit 11, connecting it to the output of the excitation current command unit 14 to form a control action on the excitation current control circuit, affect the control input of the exciter voltage control unit 12 to reduce its forcing factor.

The formation of a control action on the excitation current control loop is carried out as follows.

At idle, at low load current

where lOj, .- preset and valid

electric drive speed

Then

F

- (y mix

to

F

. F-Hi and

zs

where Uort K (-Uj cosc MciKc;

Ujc K w

do uj

 With the help of the division calculation unit 21, the value of K f, and with the help of the functional converter 22, the value.

is used to set the excitation current in regenerative braking,

From the oscillogram (Fig. 3) it can be seen that the acceleration of the electric drive in the mode of power descent occurs normally. After an effective speed of a given magnitude is exceeded, the co- mandation for braking is given. transition to regenerative braking mode, d 5 0

five

0

five

0

five

Q

For forceonan-induced} excitation current arises a dynamic speed drop. This leads to the excess of the given speed real1 {- telnaya and the command to switch to the mode of power descent. Such processes are repeated, i.e. In the process of regulation in this mode, the control angle of the power converter increases to the limit value determined by the maximum voltage of the converter in the inverter mode. When this occurs, an increase in the braking torque occurs, which also causes a decrease in speed.

When the drive is controlled by the proposed method, when switching to the regenerative braking mode, the excitation force is reduced, which provides a smoother increase in the braking torque, which eliminates the dynamic speed drop. At the same time, a control action is generated on the excitation current control loop so as to provide the necessary margin for the voltage of the power converter in the inverter mode. As can be seen from the oscilloscopes 1m (Fig. 4), the dynamic speed drop does not occur, and the electric drive operates in the steady state regenerative braking.

Thus, with the proposed control method, the required rate of increase of the braking moment is provided when switching to the regenerative braking mode, as well as the required margin for the voltage of the core converter in the inverter mode. This eliminates the slowdown and the transition of the electric drive to the setting of the self-oscillation mode.

Claims (1)

Invention Formula The control method of the thyristor electric drive of the direct current of the drawworks, according to which the speed of the electric drive is set, its actual value is measured, the target and actual speeds are compared, the error rate is determined, and at ripenFiiriipHint the actual speed is given a braking command, characterized in that, in order to eliminate self-oscillations during the descent of the cargo, the weight of the cargo is additionally determined, the mode of descent of the cargo is increased and when the weight of the cargo is in a given , S.C Z1 f-syg.2. Uw . -20 -thirty the range in the mode of lowering the load simultaneously with the application of the braking command reduces the excitation forcing ratio and changes the setting of the excitation current inversely proportional to the set speed. yy cffiaifc WO az.J ur i8CA iffi: j Compiled by V.Kuznetsova Editor S.Patrusheva Tehred M.Morgental Corrector M. Maksimishinets Order 2235/54 Circulation 583 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, F-E5, Raushsk nab., 4/5 of max ISO S-tCcJ Subscription