CS215969B1 - Wiring to evaluate the instantaneous phase angle of a stator voltage or current - Google Patents

Abstract

Connection for evaluating the instantaneous phase angle of the stator voltage or current, especially for a drive controller with an asynchronous machine and a frequency converter with pulse width modulation. The tachogenerator output for the first direction of rotation is connected to the forward input of the first counter, the output for the second direction of rotation is connected to the reverse input of this counter. Its output is connected to the first input of the adder, to whose second input the output of the second counter is connected. A source of the desired slip frequency is connected to its forward and reverse inputs. The first counter is controlled by the input signals of the tachogenerator, which senses the engine speed. The first counter has a binary number corresponding to the rotor rotation angle on its outputs. The second counter has a binary number corresponding to the phase angle increase due to the slip frequency on its output. After adding these signals in the adder, we get a number corresponding to the instantaneous phase angle of the stator frequency.

Description

The invention relates to a circuit for evaluating the instantaneous phase angle of a stator voltage or current, in particular for a drive controller with an asynchronous machine and a frequency converter and for width-pulse modulation.

There are a number of connections for summing the mechanical frequency, i.e., the speed of the asynchronous motor with the slip frequency, thereby creating a stator frequency of the motor. The wiring leads to the necessity to remove coincidences of both input signals - ie the frequency signals of the stator and the slip frequency when correctly executed. An example of such a solution is the solution shown in Art. No. 186 550 ”Connection of the controlled drive with an asynchronous machine with short armature. These connections are regularly complex and occupy a relatively large space. For some purposes, it is necessary to add a counter to obtain the instantaneous phase angle of the stator voltage. Because of their complexity, these connections are often unreliable and it is very difficult to find faults and defective components.

Said drawbacks are substantially eliminated by a circuit for evaluating the instantaneous phase angle of the stator voltage or current, according to the invention, characterized in that the tachogenerator is connected via a first counter to a first input of an adder, to whose second input a slip frequency source is connected via a second counter. The wiring output is the adder output. The advantage of the invention is the relative simplicity of the connection, which is particularly advantageous when using integrated digital circuits and when selecting a pure binary code.

The accompanying drawing shows an example of a block diagram of the invention.

The output of the tachogenerator TG for the first direction of rotation fm is connected to the forward input d of the first counter C1. which is bidirectional in this example. The output of the tachogenerator TG for the second direction of rotation fm is connected to the return input from the first counter C1. Its output is connected to the first input S1 of the adder S. The output of the second counter C2 is connected to its second input S2. On its forward d and return z input is connected the source fg, the desired slip frequency. Adder S output is wiring output.

Both counters C1 and C2 may be unidirectional and the adder S may be replaced by a parallel arithmetic unit. The pulse tachogenerator TG can be only and one output. The first counter C1 is controlled by the input signals of the tachogenerator TG, which senses the engine speed.

The first counter C1 has at its outputs a binary number corresponding to the angle of rotation of the rotor [mu] m. A corresponding signal is supplied to the second counter C2 from the desired slip frequency source fgj. The second counter C2 outputs a binary number corresponding to the phase angle increment due to the slip frequency. When these signals are added together in the adder S, it then gets a number corresponding to the current stator frequency base angle

The circuit according to the invention is useful, for example, for controlling a three-phase asynchronous motor powered by an inverter, in particular with pulse width modulation.

Claims (1)

SUBJECT OF THE INVENTION Circuit for evaluating the instantaneous phase angle of a stator voltage or current, in particular for a drive controller with an asynchronous machine and a frequency converter with pulse width modulation, characterized in that the tachogenerator (TG) is connected via the first counter (Cl) to the first input (S1) S), to whose second input (S2) the source (fgjr) of the desired slip frequency is connected via the second counter (C2), the output of which is formed by the output of the adder (S).