RU1775670C - Reversible contact-free direct-current tachogenerator - Google Patents

Abstract

Usage: measurement of angular velocity of rotation. SUMMARY OF THE INVENTION: A reversible non-contact direct current tachogenerator contains a short-circuited rotor, a stator consisting of two pairs of poles, on the first pair of which an excitation winding is placed, and Hall sensors are installed on each of the poles. The Hall sensors of the second pair of poles are connected to a constant current source, the Hall sensors of the poles with the field winding are located along the axis of symmetry of these poles, the output circuits of these sensors are connected in series - in parallel and in series with the output circuits of the Hall sensors of the other poles and connected to DC amplifier input. The output of the amplifier is connected to the power supply circuit of the Hall sensor poles with an excitation winding. 2 ill.

Description

Ј

The invention relates to techniques for measuring rotation parameters of machines, and more particularly, to devices for measuring angular velocity.

A non-contact tachogenerator is known for Hall transmitters, the magnetic circuit of which consists of a closed magnetic circuit, permanent magnets along the longitudinal axis, ferromagnetic poles along the transverse axis (electrical axes are meant). The short-circuited rotor is a cylinder of diamagnetic or magnetically hard material. At the ends of the poles of the transverse axis, Hall sensors are placed in the working gap. The point electrodes of the latter are connected to a constant current or alternating current source. When the rotor rotates in the field of permanent magnets, a transverse magnetic flux and the corresponding EMF of the Hall sensors are proportional to the angular velocity of the rotor. In order to increase the steepness of the transfer characteristic, a measuring winding is placed at the poles of the transverse magnetic circuit, the voltage of which is applied to the current electrodes of the Hall sensors.

The disadvantages of the tachogenerator are:

low steepness of the transfer characteristic at low speeds:

non-linearity of the transfer characteristic, especially with a significant dynamic measurement range;

measurement error caused by temperature dependence of the parameters of the Hall sensors and instability of the magnetic flux of excitation.

As a prototype, a reversible non-contact direct current tachogenerator was selected, containing two stator

3

3

ABOUT

poles with field winding and two poles with Hall sensors placed on them, connected to a constant current source. A short-circuit winding is located on the rotor. In order to increase the steepness of the transfer characteristic, at least two additional Hall sensors are arranged symmetrically with respect to the axis of the pole at each pole with an excitation winding. The potential electrodes of the Hall sensors belonging to each of the poles with an excitation winding are interconnected in series in the opposite direction and in series in accordance with the potential electrodes of the Hall sensors of the other poles. Additional Hall sensors are also partially penetrated by a transverse magnetic flux proportional to the rotor speed, whereby the steepness of the transfer characteristic of the tachogenerator is increased.

The described tachogenerator has the above-mentioned disadvantages, the non-linearity of the transfer characteristic caused by the corresponding dependence of the transverse magnetic flux on the angular velocity of rotation of the rotor and the non-linearity of the transfer characteristics of the Hall sensors. In addition, a large number of Hall sensors used in the tachogenerator should be attributed to disadvantages, which complicates the circuit and makes the device more expensive.

The aim of the invention is to remedy these drawbacks, namely, increasing the accuracy, steepness of the transfer characteristic and expanding the dynamic range of measurement,

This goal is achieved by the fact that in the well-known reversible non-contact direct current tachogenerator containing a short-circuited rotor, a stator consisting of two pairs of poles, the first pair of which contains an excitation winding, and potential sensors are installed on each of the poles in the working gap, the electrodes of which are interconnected, and an indicator, while the Hall sensors installed on the second pair of poles are connected to a constant current source, a constant current amplifier is introduced, and Hall sensors and the first pair of poles are mounted symmetrically with respect to the longitudinal axis of these poles, while the potential electrodes of the Hall sensors in pairs are connected in series according to each other, and between the pairs are connected in series, the potential electrode of one of the Hall sensors of the second pair of sensors

connected to the first input of the amplifier, to the second input of which a potential electrode of one of the sensors of the first pair is connected, current electrodes of the sensors

The halls of the first pair are combined in pairs, with one pair of combined current electrodes connected through an indicator to the first output of the DC amplifier, and the other to the second output of the same

0 amplifier.

In FIG. 1 shows a cross section of a tachogenerator; in FIG. 2 is a circuit diagram of the inclusion of Hall sensors.

5 The reversible non-contact direct current tachogenerator is an electric machine with a squirrel-cage rotor 1, a stator 2 with two pairs of poBi. Excitation winding 4 is placed on diametrically opposite cavities 3 of the first pair. Hall sensors are installed on the poles 5 of the second pair in the working gap 6 and 7. At the poles of the first pair, Hall sensors 8 and 9 are also installed symmetrically

5 relative to the longitudinal axis of these poles. Potential electrodes of Hall sensors in pairs are interconnected in series according to. One of the potential electrodes from the second pair of sensors

0 is connected to the first input of the DC amplifier 10, to the second input of which a potential electrode of one of the Hall sensors of the first pair of sensors is connected. Current electrodes of Hall sensors 8, 9

5 of the first pair are combined in pairs, moreover, one pair of these electrodes is connected through an indicator 11 to the first input of the DC amplifier 10. the other to the second output of the same amplifier. The current electrodes of the Hall sensors b, 7 of the second pair are also pairwise connected and connected to a constant current source 12. The Hall sensors in each of the pairs are selected so that from the total residual voltage to

The 5 potential electrodes were close to zero.

The tachogenerator operates as follows. The excitation winding 4 generates along the axis of the first pair of poles 3 a magnetic flux Фb, which penetrates the rotating rotor 1 and induces an EMF in its winding. The rotor winding current caused by this EMF creates a stationary magnetic flux of the PSF along the axis of the second pair of poles 5 poles 5. The PSF also penetrates the rotor, causes the corresponding EMF and current in its winding, and the latter - the magnetic flux along the axis of the first pair of poles, the secondary reaction of the rotor . As a result, the magnetic flux along the axis of the first pair of poles is reduced to a value. Oq flow, acting on Hall sensors 6, 7 creates an EMF on their potential electrodes

Eq Kq In. f l (t) Bq,

where Kq is the sensitivity of the sensors to magnetic induction;

In is the sensor supply current;

fi (t) is a function describing the effect of temperature on the sensitivity of Hall sensors;

Bq is the magnetic induction in the working gap of the second pair of poles.

Similarly, the Od flow, acting on Hall sensors 8 and 9, creates EMF on their potential electrodes

Ed Kd Bbixf2 (t) Bd,

where Kd, f2 (t) are similar parameters, respectively, Kq and fi (t);

o - the output current of the amplifier;

Bd is the magnetic induction in the working gap of the first pair of poles. 25

The difference between the EMF A E Eq - Ed is applied to the input of the DC amplifier 10.

Amplifier output current

lBWx (Eq-Ed) 30

KyKqlnMOBq

1 + KyKdf2 (t) Bd

where Ku is the gain of the amplifier. 35 Having ensured the appropriate choice of Ku the relation KyKdf2 (t) Bd 1 (at the lowest value of Bd), get

IBblx Rqfl (t) Bqln / Kdf2 (t) Bd

In the manufacture of Hall sensors from the same material and using the same technology, it should be expected that the ratio Kqf i (t) / Kdf2 (t) will be practically stable 45 with a change in temperature and magnetic induction acting on the Hall sensors.

Denoting the above ratio by Ko, get 50

i - k i Bq

OUTPUT - “Ч In r

-

3d fd

SqOd

where Sd, Sq are the cross-sectional areas of the poles.

Magnetic flux values

F0

  Gq g0 fi t go Gd Gq a + 1

10

fifteen

5

0

5

0

5

0

5

Od

Fi

0

to Gd Gq o / 2 -f 1

where Gq, Gd are the magnetic conductivities along the axis of the second and first pairs of poles; d0 is the electrical conductivity of a part of the rotor winding bounded in the tangential direction by a dihedral angle of one radian.

Substituting the values of Oq and Od in the formula for 1out, get

 Out Ko In K - Gq go (L.

iq

The last expression shows that the output signal is the current of the amplifier 10. measured by the indicator 11. is directly proportional to the angular velocity of rotation of the rotor o), i.e. the transfer characteristic of the tachogenerator is linear.

In the tachogenerator-prototype, there is a nonlinear dependence of the flow of the PSF on o, which is the main reason for the non-linearity of its transfer characteristic. To reduce the degree of nonlinearity, the parameters of the prototype tachogenerator are chosen in such a way as to ensure

satisfying the inequality go2GqGd 1 / ffl§ where fiAj is the measurement limit of the tachogenerator. This decreases the steepness of the transfer characteristic. In this tachogenerator, there are no restrictions on the choice of parameter values g0, Gq, and Gd, which makes it possible to choose them optimal and to provide a significantly greater steepness of the transfer characteristic compared to the prototype with the same degree of nonlinearity. So, in the tachogenerator prototype, to ensure the degree of nonlinearity in magnetic flux,

more than 1% accept go2GqGd 0.04 / ojS. In this tachogenerator, parameters can be selected based on the ratio g02GqGd

 1 / j) §, which will provide an increase in the steepness of the transfer characteristic by a factor of 5 compared with the prototype with the same degree of non-linearity or with the given parameters, the dynamic range of the measurement will also be expanded by a factor of 5.

The tachogenerator has the following advantages: increased linearity of the transfer characteristic with the same sensitivity as the prototype, or greater sensitivity with the same non-linearity of the transfer characteristic with the prototype;

large dynamic measuring range;

less error caused by a change in the excitation flux and the influence of temperature on the parameters of the Hall sensors;

fewer Hall sensors.

Claims (1)

SUMMARY OF THE INVENTION A reversible non-contact direct current tachogenerator comprising a short-circuited rotor, a stator consisting of two pairs of poles, the first pair of which contains an excitation winding, and Hall sensors, potential electrodes of which are installed on each of the poles in the working gap interconnected, and an indicator, while the Hall sensors installed on the second pair of poles are connected to a constant current source, characterized in that, in order to increase / Fig 2 accuracy, steepness of the transfer characteristic and expansion of the dynamic range of measurements, a DC amplifier is additionally introduced into it, at the potential electrodes of the Hall sensors in pairs are connected to each other in series according to each other, and between the pairs are connected in series to each other, and one of the potential electrodes of the Hall sensors from the second pair of sensors connected to the first input of the amplifier, to the second input of which is connected a potential electrode of one of the Hall sensors from the first pair of sensors, the current electrodes of the Hall sensors are the first pairs of sensors are paired together, with one pair of combined current electrodes connected through an indicator to the first output of the DC amplifier, the other to the second output of the amplifier direct current, with Hall sensors of the first pair of poles installed symmetrically with respect to the longitudinal axis of these poles.