CS233724B2 - Method to prevent d-c electric motor from overload utilizing checking of effective current and electronic fuse to perform the method - Google Patents

Abstract

In a method of monitoring the effective current in direct current electrical machines to prevent overloading, a quantity representing the actual current (Iist) is squared; and a quantity representing the square of the rated current (I<2>N) is subtracted from the square of the actual current (I<2>ist). The difference is integrated over time, and the integrated value is indicated as a measure of the loading of the drive. This measurement may be used to control the load. <IMAGE>

Description

The present invention relates to an effective current method in DC electrical overload prevention machines in which ae produces the square of the actual current. The invention further relates to an electronic fuse for carrying out the method, which comprises an actual current quadrator and an integrator.

The effective current control of DC electrical machines, if any, was performed using complex electronic counting circuits. This type of tulle control is realized and only feasible with expensive equipment. Setting up these devices was very time-consuming, since many of the initial data of the monitored device had to be determined for their function.

DE-OS 29 22 197 discloses an automatic overload tripping device for controlling the electrical comfort, preferably for motors of motor vehicle antennas.

which is expected to limit the maximum torque of the motor, whereby the overload of the engine speed * decreases below a certain limit as a criterion for switching off the drive. In this case, the torque limitation is effected by means of electronic circuits, namely by a circuit for current dissipation.

It is known from CH-A 591 775 to protect the rotor of an electric machine against excessive temperatures, which comprises a quadrature for generating the square of the actual current and an integrator. However, since the circuit according to the present invention has been found, it is unlike other, more complicated and not so precise generation of a certain value from the corresponding circuits.

Also known from SU-Author's Certificate 675 517 is known for protecting electric motors against excessive temperatures, which comprises a quadrator for generating a second actual current moerdna and an integrator. However, even this device is considerably more complex from the national point of view to the peripheral elements compared to the present invention.

The object of the invention is to provide a method koxntroly effective current in stetno8eěrtých electric machines for zammzení overload and electronic fuse py implementing such method ^kt Zr ^eh by using ^the ontrol ^y z ^ k ^ in ^ current value detected zatlení actuator and the actuator is protected against overloads .

According to the invention, this object is achieved by subtracting the square of the nominal current from the square of the actual current and integrating the difference according to the wafer, the integrated value being indicated as a mra of the load of the drive and used for load control.

An electronic fuse comprising an actual current quadrator and an integrator is used to perform the method, and the subtlet is based on the fact that a differential circuit is connected to the output of the quadrature to produce a difference between. connected to the longer input of the differential circuit, the output of the differential circuit is connected not to the integrator, not to the outputs of which both the indicator and the threshold control circuit are connected.

A preferred embodiment of the electronic fuse is that the output of the threshold control circuit is connected to an optical or acoustic indicator device.

By using the electronic overload fuse according to the invention, which is based not on the rated current, a simple, high-level information check is provided for the operator of the device, and at the same time an effective overload protection is ensured.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, in which the electronic fuse according to the invention is shown in block form. *

The electronic fuse consists of a quadrator 1, the output of which is connected to one input of the differential circuit g. Not the other input of the differential circuit 1 is connected to a constant voltage source 2. The output of the differential circuit 2 is connected to an integrator 8, one output of which is connected to the threshold control circuit 2 and the other output to the indicator 6. An indicator device 6 may be connected to the threshold control circuit 2.

The actual current ae feeds the quadrator 1 where the square of its value is generated. Quads 1 is connected to a differential circuit 2 »in which the square of the rated current Γν 2 2 subtracted from the square of the actual current TIBtech · Square rated current is 1.2 ^ ^b přivádlěna odečítecímu of water from the source 2 £ boMtentního voltage.

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When a positive difference occurs (IJ _et “ijp * 0, this difference is integrated in the integrator 4 over time. The content of the integrator £ is shown in the indicator χ. The value indicated is a measure of the time it takes to mow before the machine is checked can burden.

At the same time, the content of the integrator is compared in the electronic control circuit 2 threshold. values. A value of 0 indicates the optical or acoustic device £, this can fall at ^x ^ enálkou that the machine is ready to work.

At a value> 0, due to the risk of thermal overload, restarting the machine should be avoided until the value is = 0 or ≥ 0, which is achieved after a certain pause. Pro. for this purpose, an automatic re-lock can be provided.

The described connection function can also be achieved - with digital technology elements.

Claims (3)

SUBJECT OF THE INVENTION 1. A method of controlling the effective current of a DC overload avoidance machine in which a second true current power is formed, characterized by subtracting a second power current (Ij) from this second current current (1 ^^) ^. and cut the int e ^{g p} oestrus ccording tesa, wherein tategrovará hotoota with the ^ melts as a measure of load on the drive and is used to konarole zetížení. 2. An electronic fuse for carrying out the method of claim 1, both comprising an actual current quadrant and an integrator, characterized in that a differential circuit input (2) is connected to the output of the quadrator (1). to create the difference between the square of the real current Me Λ (iist) ^{8 me2} * i squared of rated current (ij) from constant power supply (2) connected to other input of differential circuit (3), output of differential circuit (2) is connected to input of integrator (4), one output of it is connected to the indicator (7) and the other to the threshold control circuit (5). 3. The electronic fuse according to claim 2, characterized in that the threshold value control circuit (5) is equipped with an optical or acoustic indicator device (6).