SU1038893A1 - Device for determination of ac electrical machine dynamic inductive resistance - Google Patents

Abstract

DEVICE FOR DETERMINATION. DYNAMIC INDUCTIVE RESISTANCE OF WINDOWS OF ELECTRIC AC MACHINES, containing an adjustable DC power supply unit connected via a switching device and a measuring shunt to the windings of the machine, the measuring unit I connected to the contacts of the switching device and the measuring shunt to the windings of the machine, the measuring unit I connected to the contacts of the switching device and the measuring shunt to the windings of the machine, the measuring unit I connected to the contacts of the switching device and the measuring shunt to the windings of the machine, the measuring unit I connected to the contacts of the switching device and the measuring shunt to the windings of the machine, the measuring unit I connected to the contacts of the switching device and the measuring shunt to the windings of the machine, the measuring unit I connected to the contacts of the switching device and measuring shunt , increasing productivity and reducing the measurement time, it is equipped with a comparator connected in series with the control pulse shaping unit and with a muting unit, also equipped with a non-inverted input connected to a measuring shunt by a logarithmic amplifier, the inverse input of which is connected to a reference voltage source, and the output connected to the first input of an analog signal's quick storage unit and a measurement unit, the output of the high-speed memory generator of an analog signal, which is erased. memory, the output of which through the nonlinearity unit is connected to the measurement unit, and the second inputs of the analogue blocks are memorized and connected to the output of the control pulse shaping unit. o 00 90 00 so oe

Description

The invention relates to electric machines and can be used in all parts of the national economy for measuring the inductive resistances of the windings of AC electric machines at the initial moment of a sudden change in mode.

A device for determining the dynamic inductances and the inductance of windings, which contains a capacitor, a source of direct current, a series-connected controlled winding and a ballast winding with a known inductance, is known. The maximum inductance value is determined from the maximum value of the voltage measured on the controlled winding.

However, this device imposes limitations on the type of DC voltage source, since, in accordance with the essence of physical phenomena, it requires power supply only from a charged capacitor, excluding a DC or rectifier device} requires the inclusion of an additional element in the basic circuit of the equipment under test. - ballast inductive resistance, the value of which must be matched with the value of the inductance of the controlled electric machine.

The closest in technical essence and the achieved result to the proposed is a device for determining the dynamic inductive resistances of the windings of electric machines of alternating current, containing an adjustable DC power supply unit connected through a switching device and measuring shunt to the windings of the machine, the measuring unit connected to the contacts switching device and measuring shunt 12.

The disadvantages of this device are that to determine the inductive resistance of an electric machine, measured from the side of the stator or rotor winding at the first moment of the mode change, it is necessary to perform a significant number of operations: to register the transient function, measure the transient function, approximate the transient function, determine the derivative of the transition function in the first moment of its change. This disadvantage causes a decrease in the accuracy of measurement of the derivative with relatively large labor costs and the time required to determine the dynamic inductive resistances.

The purpose of the invention is to increase accuracy, increase productivity and reduce the time required for the dynamic inductive resistance of the windings of ac electric machines.

This goal is achieved by the fact that a device for determining the dynamic inductive resistances of the windings of electric machines, comprising an adjustable power supply unit, a direct current connected via a switching device and a measuring shunt to the windings of the machine, a measuring unit connected to the contacts of the switching apparatus and the measuring shunt, it is equipped with a comparator connected in series with a control pulse shaping unit and with a switching device, also equipped with a measuring device A shunt is a non-inverted input with a logarithmic amplifier, the inverse input of which is connected to a reference voltage source, and the output is connected to the first input of an analog signal high-speed memory unit and the measuring unit, the output of an analog signal high-speed memory unit is connected to the input of a long-term memory unit, the output of which is the nonlinearity unit is connected to the measurement unit, and the second inputs of the analog memory units are connected to the output of the control pulse shaping unit.

FIG. 1 shows a block diagram of a device for determining the dynamic inductive resistances of windings of electric machines of alternating current; in fig. 2 - characteristics of analog signals.

The device contains an adjustable DC power supply unit 1 of the electric machine windings 2. switching device 3 and measuring non-induction shunt 4, logarithmic amplifier 5, which is a four-link logarithmic converter, in which a piecewise linear and piecewise nonlinear approximation of the logarithmic characteristic is combined, which allows to ensure high accuracy of conversion, a fast-acting comparator b, block 7 formation of controlled pulses, the block of fast-acting storage of the analog signal 8, which is an amplifier with a large input impedance, The amplitude-frequency characteristic of which is provided by connecting the capacitance to the output of the amplifier, and the capacitor serves both for storing and correcting, the long-term storing of the analog signal, the non-linearity unit 10, which implements the inversely proportional dependence, the measurement unit 11.

The device works as follows.

From the output of the power supply unit 1 through the measuring shunt 4, the coil 2 of the electric machine is supplied with a constant current of a given value v. Measurement unit 11 is alternately connected for measuring voltage to measuring shunt 4 and contacts of switching device 3, and then to output of unit 5. By adjusting the magnitude of the reference voltage, a voltage equal to zero is set at the output of unit 5. Switching device 3 is turned on, as a result of which DC current is attenuated in the stator windings 2 of the stationary machine (Fig. 2, curve 1). At the output of block 5, a voltage change follows the logarithmic law. 2, curve 2J. The disappearance of the voltage between the contacts at the time of switching on the switching apparatus 3 is recorded by the high-speed comparator b, which triggers the control pulse generation unit 7, which after a predetermined time interval l-t generates a control pulse. With the arrival of the control pulse, blocks 8 and 9 sample the analog signal, and block 9 and long-term memorization (Fig. 2, curve 3). Since the change in current in a short-circuited winding circuit of an electric machine at the initial stage of attenuation can be described with high accuracy equivalent to the attenuation coefficient ot, then (tl enioe e i -ott.

and about

The constant component C i is compensated when the reference voltage is applied - I to the inverse input of the block 5.

Thus, when choosing the coefficient of force at the input of block 10 equal to ui-r-, the value of the analog signal at its output will be equal to m-, which corresponds to the well-known expression for the super-intermediate inductive resistance

0

.

. Where T is the current decay time to Nu l on the initial tangent. The magnitude of the active resistance 5 of the attenuation circuit is determined by;

about

rssh

where Rj, i is the voltage of shunt 4;

0

voltage measured on shunt 4 before switching on switching device 3;

and the voltage measured on the contacts of the commuting

5 apparatus 3.

The use of the proposed device for determining the dynamic inductive resistances of AC electric machines makes it possible, compared to lime, to increase speed by eliminating the oscillography operation and the time-consuming operation of processing oscillograms by manual measurements.

5 | transition function of a significant number of points in time, moreover, to increase the accuracy of determining dynamic inductive resistances, since it eliminates experimental data, which are obtained with handheld transducers.

Claims (1)

DEVICE FOR DEFINITION. OF DYNAMIC INDUCTIVE RESISTANCE OF AC ELECTRIC MACHINE WINDING, containing an adjustable DC power supply connected through a switching device and a measuring shunt to the windings of the machine, a measuring unit connected to the contacts of the switching device and a measuring shunt, which is characterized in order to increase the accuracy that To increase productivity and reduce measurement time, it is equipped with a comparator connected in series with the unit "" of the formation of control pulses and commutated The logging amplifier is also equipped with a non-inverse input connected to the measuring shunt, a logarithmic amplifier, the inverse input of which is connected to the reference voltage source, and the output is connected to the first input of the high-speed memory unit of the analog signal and the measurement unit, the output of the high-speed memory unit of the analog signal is connected to the input of the long-term unit memory, the output of which through the nonlinearity block is connected to the measurement block, and the second inputs of the analog memory blocks are connected to the output of the control pulse generation unit.