RU2491706C1 - Device to stabilise rotation frequency of single-phased commutator motor - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: square root calculator is introduced into the feedback channel thus forming quadratic function of feedback signal and hence valid voltage value changes as a square root function of electromagnetic torque of the motor at constant speed, and accordingly optimal control law for the electric drive is ensured as regards maximum performance efficiency in dynamic modes.

EFFECT: improvement of energy indicators for electric drive.

1 dwg

Description

The invention relates to electrical engineering and, in particular, to an electrified tool, household and industrial electrical appliances, devices for special purposes.

A device is known (http://www.coilgun.ru/920/regulator.gif) for automatically stabilizing the rotational speed of a dc sequential excitation electric motor, which includes a sawtooth voltage generator (GPN), a circuit for comparing the signal from the output of the GPN with a feedback signal and a pulse-width converter for controlling engine speed. The disadvantage of this solution is that it does not respond to a number of disturbances (for example, deviations of the voltage of the power source and the heating temperature of the motor windings), since it does not control the output coordinate - the frequency of rotation of the electric motor.

Closest to the claimed solution, according to the applicants, is a device for implementing a method of stabilizing the rotational speed of a single-phase collector motor according to as USSR No. 997216, Н02Р 5/12 dated 02.15.83, the device contains an electric DC motor with series excitation, included in the diagonal of a semi-controlled valve bridge (power amplifier) and shunted by a reverse diode and discharge resistor, the common point of which is connected to the input of an intermediate amplifier, consisting of an operational amplifier and a transistor, the output of the intermediate amplifier being the input of an integrator consisting of a transistor and a capacitor that is connected to the input of the switching device a solid, performing the functions of a power amplifier control unit, including a capacitor, on which a given voltage is generated, a transistor, the unlock voltage of which is a reference voltage.

The disadvantage of this device is that in dynamic modes of operation the value of the coefficient of efficiency (COP) of the stabilization system of the rotational speed of a single-phase collector motor is quite small, while the main mode of operation of such an electric drive is dynamic mode, while the maximum value of efficiency will be at nominal values of current and voltage, for which the engine was calculated.

The technical result of the proposed solution is to increase the efficiency of the electric drive in dynamic modes.

This goal is achieved by the fact that a device for calculating the square root (quadrator) is introduced into the feedback circuit (Bobrovnikov LZ Radio engineering and electrical engineering. / LZ Bobrovnikov. - 4th ed., Ext. And revised. - M. : Nedra, 1990, p. 172), which forms a quadratic dependence on the feedback signal, and in proportion to the output signal of the quadrator, the effective value of the motor voltage at the output of the SHIP changes.

Figure 1 presents a diagram of a device for stabilizing the speed of a single-phase collector motor.

A device for stabilizing the rotational speed of an electric motor comprises an uncontrolled rectifier 1, a pulse-width converter 2, a dc motor of series excitation 5, shunted by a reverse diode and a discharge resistor, the common point of which is connected to the control system 6, which determines the rate of decay of the self-induction EMF, quadrator 4, which generates a control signal for a switching device proportional to the square root of the electromagnetic moment of the motor, and a switching device Property 3, which generates a control signal of a pulse-width converter for regulating the width of the applied pulse of the rectified supply voltage.

The device operates as follows.

At a time when the transistor included in the pulse-width converter 2 is turned off, the electric motor can be considered disconnected from the network and, if its circuit is closed to a discharge resistor, for the formed motor-diode-resistor circuit, one can write the equation

$$L\cdot \frac{di\left(t\right)}{dt}+e\left(t\right)+\left(R_{\mathrm{I\; am}}+R_{\mathrm{about}\mathrm{at}}\right)\cdot i\left(t\right)=0\begin{array}{ccc}& & \end{array}\left(\mathrm{one}\right)$$

$$e\left(t\right)=k_{F}c\cdot \omega \cdot i\left(t\right),\begin{array}{cccc}& & & \end{array}\left(2\right)$$

where e (t) is the EMF of the engine armature;

C is the structural constant of the electric motor;

k _Ф - proportionality coefficient between armature current and magnetic flux;

R _I , R _s - resistance windings of the armature and excitation;

ω is the frequency of rotation of the motor shaft, 1 / s;

L is the inductance of the electric motor circuit, GN.

With great accuracy, we can assume that L = const, since the current i (t) of the armature is caused by the action of the self-induction EMF and is about 10-15% of the nominal current I _n . For the same reason, and k _Ф = const.

Time t ₀ , at which the current defined by equation (1) vanishes, and therefore vanishes and the self-induction EMF is, with a high degree of accuracy, proportional to the load current and inversely proportional to the engine speed. The time interval from π to π + ωt ₀ corresponds to the width of the voltage pulse across the discharge resistor shunting the motor (5), which is fed to the input of the control system (6), determining the rate of decline of the self-induction EMF. The output signal of the control system (6), containing information on the angular frequency of rotation of the engine, is fed to the input of a quadrator (4), in which a signal is generated proportional to the square root of the electromagnetic moment of the engine. The generated signal is fed to the input of the switching device (3), which generates control signals for the transistors of the pulse-width converter.

The necessity of generating a feedback signal as a function of the square root of the electromagnetic moment of the motor is determined by the optimal, from the point of view of ensuring maximum efficiency in dynamic modes, control of a single-phase collector electric motor.

To determine the control criterion, we consider the structure "controlled converter - sequential excitation engine" in relative units:

; $$\mu =\frac{M}{M_H}=i^2$$

; $$\nu =\frac{\omega }{{\omega }_H}$$

; $$u=\frac{U}{U_H}$$

; $${\mu }_C=\frac{M_C}{M_H}$$

; $$\tau =\frac{t}{T_M}$$

; $$T_M=\frac{J\cdot {\omega }_H}{M_H}$$

; $$\rho =\frac{R_{Я}}{R_H}$$

$$i=\frac{I}{I_H}=\sqrt{\mu }$$

; $$\mu =\frac{M}{M_H}=i^2$$

; $$\nu =\frac{\omega }{{\omega }_H}$$

; $$u=\frac{U}{U_H}$$

; $${\mu }_C=\frac{M_C}{M_H}$$

; $$\tau =\frac{t}{T_M}$$

; $$T_M=\frac{J\cdot {\omega }_H}{M_H}$$

; $$\rho =\frac{R_{\mathrm{I\; AM}}}{R_H}$$

Then the basic equation of motion of the electron beam in the system of relative units has the form:

$$\mu =\frac{d\nu }{d\tau }+{\mu }_c$$

The task of optimal control of the electric drive can be formulated as follows: change the motor speed from the value ν ₁ to ν ₂ so that for an arbitrary time of the transition process the energy consumed from the converter is minimal. For this, it is necessary to provide maximum dynamic efficiency:

$$\eta \left(\tau \right)=\frac{{\displaystyle \int \left({\mu }_c\cdot \nu \right)\cdot d\tau }}{{\displaystyle \int \left({\mu }_c\cdot \nu +\Delta P\right)\cdot d\tau }}$$

where ΔР is the loss in the electric field: electrical ΔР _el and mechanical ΔР _mech .

Obviously, the maximum of this functionality will be provided under the following condition:

$${\displaystyle \int \left({\mu }_C\cdot \nu +\frac{u^2}{\rho }+\Delta P_{MEX}\right)}d\tau \to \min$$

Expressing dτ from the equation of motion and replacing the integration limits, we obtain

$${\displaystyle \underset{0}{\overset{{\tau }_{PP}}{\int }}\left({\mu }_C\cdot \nu +\frac{u^2}{\rho }+\Delta P_{MEX}\right)}d\tau ={\displaystyle \underset{\nu \mathrm{one}}{\overset{\nu 2}{\int }}\nu \cdot \left({\mu }_C+\frac{u^2}{\rho }+\Delta P_{MEX}\right)\cdot }\frac{d\nu }{\mu -{\mu }_C}$$

In those cases when µ _C is a function of speed and does not depend explicitly on time and path, the minimum of a certain integral is achieved provided that for each value of speed in the interval ν ₁ -ν _{2 the} motor moment provides a minimum of the integrand

$$\frac{d}{d\mu }\left[\raisebox{1ex}{$\left(\nu \cdot {\mu }_C+\frac{u^2}{\rho }+\Delta P_{MEX}\right)$}\!\left/ \!\raisebox{-1ex}{$\mu -{\mu }_C$}\right.\right]=0$$

Find the derivative and express the stress, neglecting mechanical losses:

$$u=\pm \sqrt{a\cdot \mu }$$

where a = ν · ρ.

Thus, the claimed technical result is achieved due to the fact that a multiplier dividing device is introduced into the feedback channel, forming a quadratic function of the feedback signal, and thereby the effective voltage value changes as a function of the square root of the electromagnetic moment of the engine at a constant speed, and therefore provides the optimal, from the point of view of ensuring maximum efficiency in dynamic modes, the law of control of the electric drive.

Claims (1)

A device for stabilizing the rotational speed of a single-phase collector motor, comprising a series-direct current DC motor, fed from a pulse-width converter and shunted by a reverse diode and a discharge resistor, the common point of which is connected to the input of the control system, which contains an intermediate amplifier consisting of an operational amplifier and a comparator and transistor, and the output of the intermediate amplifier is the input of an integrator consisting of a transistor and a capacitor, cat The first one is connected to the input of the switching device, which generates a control signal for a pulse-width converter, including a capacitor, on which a given voltage is generated, a transistor, the supply voltage of which is a reference voltage, characterized in that the device contains a square root calculator that generates a switching control signal a device that controls the transistors of a pulse-width converter in such a way that the effective voltage value is supplied I single-phase commutator motor varies as a function of the square root of the electromagnetic torque of the engine, and a power amplifier consists of an uncontrolled rectifier and PWM inverter.