SU1275728A1 - Device for determining rotational speed of d.c.electric motor - Google Patents

Description

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The invention relates to electrical engineering and can be used to measure the frequency of rotation of a DC motor.

The purpose of the invention is to improve accuracy.

FIG. 1 depicts a structural

The diagram of the device in FIG. 2 is a view of the output signal of the device.

A device for determining the frequency of rotation of the direct current motor 1 includes a measuring resistor 2, which is connected in series with the electric motor 1, a current sensor 3 whose inputs are connected to the measuring resistor 2, a voltage sensor 4 whose inputs are connected to the electric motor 1, the adder 5, C The purpose of increasing accuracy in the device is input 1 element 6 with dead band, connected between voltage sensor 4 and the first input of adder 5, comparison element 7, relay element 8, aperiodic element 9 an inverting scale element 10, wherein the voltage sensor 4 is connected via the element 6 to the dead zone connected to the first input of the adder 5, the output of which through the aperiodic link 9 is connected to the inverting input of the comparison element 7, the non-inverting input of which is connected to the current sensor 3, the input the relay element 8 is connected to the output of the element 7 of the comparison J, and the output is connected to the secondary. to the input of the adder 5 and connected via the inverting scale element 10 with the output of the device,

The device works as follows

The equation for the dynamic electromechanical characteristics of an electric dc motor of an independent excitation is;

L

 -r.)

dt

where 1 is the current of the motor core;

and - voltage on the engine bark;

Gd - active resistance Ld - inductance of the root chain Kg - coefficient depending on. type of engine.

The device is an electronic model of a 1J motor operating on a real scale2757282

Be time and described by the equations:

§§ - r. V;

V V signii;

(one)

d1 i -

and U.-luUisignU;

where i is the calculated model current; 4,1 - current mismatch

electric motor and model; V is the output signal of the relay element B;

 - permanent positive

J factor

and a is the voltage at the output of the voltage sensor 4;

. uU is the magnitude of the dead zone of the element 6. The electric motor 1 current is determined by measuring the voltage drop across the low-resistance resistor 2. The calculation of the model current 1 from the first equation of system (1) is performed using the adder 5 and the aperiodic link 9, second uranium is solved by the relay element 8, the third by the comparison element 7.

The voltage drop in the brush contacts is simulated by the dead zone element 6 (fourth equation of system (1)).

If in the model described by equations (1), current tracking (sliding mode) occurs, i.e. and, then the average value of the signal V is equal to:

  -Ke

The V signal is broken (time-modulated).

For that; so that the device has a sliding mode on line A, f is necessary and sufficient for dbi

4 Op i. so that u, i

Ai dt, dAi had different signs. Because

dt

Ai- y

j. .d signui,

then the condition of different signs is observed when V j -tj, ui-KgQJ, which is practically possible to fulfill always. In fact, the second input of the adder 5 is supplied with a value equivalent to the emf of rotation of the electric motor 1, with the opposite sign.

Claims (1)

Claim A device for determining the rotational speed of a direct current electric motor, comprising a measuring resistor connected in series with the electric motor, a current sensor whose inputs are connected to the measuring resistor, and a voltage sensor whose inputs are connected. to an electric motor, an adder, characterized in that, in order to increase accuracy, an element with a dead zone is inserted into it, connected between the voltage sensor and the first input of the adder, a comparison element, a relay element, aperiodic (a link and an inverting scale element, the input of which is connected with the output of the relay element and the second input of the adder, the output connected to the input. ^! an aperiodic link whose output is connected to the first input of the comparison element, whose second input? connected to the output of the current sensor, and the output is connected to the input of the relay element.