? ' c c ? 7 4 - 1 Process for controlling the feed of a drum cutter-loader
during mining The invention relates to a process for controlling the feed of a drum cutter-loader during mining.
It is known in the case of a drum cutter-loader for the feed to be controlled in dependence upon the power input of the cutting drums, in order to match the feed velocity to the respective operating conditions, more especially to the hardness of the coal or such like being mined. The control devices used for this purpose usually comprise a frequency converter, via which the feed drive mechanism can be controlled in its speed by frequency variation.
With such arrangements for controlling the feed velocity it is advantageous to control the current of the more highly loaded cutting motor in each case to the nominal value via the feed velocity. If the feed control is accommodated in the heading, signals which are proportional to the currents of the cutting drum motors must be transmitted from the cutter-loader to the heading. If here, in order to avoid a special data channel, the signals are connected into an already existing one, control difficulties may occur on account of the transmission times resulting therefrom. It is an object of this invention to provide a remedy to this problem by controlling the feed of a cutter- loader during mining, in such a way that it is possible to intervene briefly in the control of the feed velocity even with sudden overloading of the cutting drum motors, in order 2 to be able to reduce the rate of feed as rapidly as possible so as to avoid damage to the motor. This possibility of intervention is intended to be provided not only for plants with an existing data channel between cutter-loader and parallel heading, but also for plants without such a data channel.
According to the invention, from one aspect there is provided a process for controlling the feed of a drum cutter-loader in mining, with two cutting drums driven independ-ently of each other, with current systems, which are independent of each other, for the cutting drums on the one hand, and the feed on the other hand, and with an electronic device for regulating the rate of feed in dependence upon the loading of the cutting drum motors, wherein a) signals are derived in the cutter-loader as functions of the single currents of the cutting drum motors and are transmitted to the regulating device in the h parallel heading, b) the signals determined are continuously compared with the nominal value of each single current, and in the event of there being any exceeding of such nominal values, the nominal value predetermined for the control of the feed is reduced for a corresponding reduction of the rate of feed, c) moreover, the signals determined are continuously limited to the nominal value of the single currents of the cutting drum motors, and a total signal is formed 3 is therefrom, and d the total signal is compared with a signal measured in the parallel heading as a function of the actual total current of the two cutting drum motors and in the event of a sudden variation between the two comparison signals, the predetermined nominal value is reduced, and as a result, a reduction of the rate of f eed is brought about.
By such a process of the invention, a continuous control of the individual currents of the cutting drum motors is provided for, the rate of feed being automatically reduced when it is ascertained that a nominal value has been exceeded. Gradually occurring load increases of the cutting drum motors can be logged. In order to be able to take sudden overloads into account also, the total current which can be measured in the parallel heading is also continuously compared with the sum of the two individual currents of the cutting drum motors which are limited to the nominal current and counter-controlled, so that the speed of the feed drive mechanism is reduced when variations are ascertained.
If transmission of the individual currents of the cutting drums into the area of the parallel heading is not possible, another solution to the problem is proposed which consists in that on the one hand, the sum of the two currents of the cutting drum motors is logged in the parallel heading and on the other hand the reactance portion of the total current is logged continuously, and that from the comparison of the amplitudes of total current and 4 reactance current there is derived a signal by means of which, in the event of an overload of at least one of the cutting drum motors, a reduction of the rate of feed is initiated.
This solution originates from the following knowledge.
With uneven loading of the two cutting drum motors, the resulting total current is not adequate for the feed control. The reactance portion of the total current is added in order to estimate the current distribution, according to the invention. From the amplitudes of total current and reactance current, the overloading of one of the two motors can be determined and thus an immediate reduction of the rate of feed can be introduced in each case.
The invention may be performed in various ways and a preferred embodiment will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 shows a general diagram of an arrangement for controlling a drum cutter-loader in a first embodiment; Figure 2 shows an electrical block circuit diagram for the arrangement as shown in Figure 1; and Figure 3 shows an electrical block circuit diagram of an arrangement for controlling a drum cutter-loader during mining, in another specific embodiment.
A drum cutter-loader 1 as indicated in Figure 1 is used in an extraction longwall face and is equipped with two cutting drums 2 and 3, which are driven in each case by a three-phase motor 4 and 5. The feed drive mechanism can be k designed in a customary way, f or example as a rack drive. In this example it is assumed that the feed is produced by two three-phase motors 6 and 7.
From the currents of the cutting drum motors 4 and 5 proportional signals h and i are logged in the cutter-loader 1 and connected to an existing data channel of the coal cutter cable 9 together with further measuring signals which are not relevant for the control system.
In the area of the parallel heading there are a transformer 10 for the energy supply to the cutter-loader 1, a compact station 11 with a flange-mounted heading station 12, a frequency converter station 13 and a terminal box 14. The control of the arrangement from above ground by a control post 15 is also possible.
A control system 16 which is in the heading station 12 splits up the signals coming from the cutter cable 9 via a data connection 17 and transmits the signals via a connection 18 to the control post 15. From the transmitted current signals h and i of the motors 4 and 5 and also from the total current p of the motors 4 and 5 a nominal value _q is formed and communicated to the frequency converter 13. The frequency converter 13 controls the speed of the feed motors 6 and 7 via its control and regulating device 19 and its inverter 20, in dependence upon the nominal value _q.
The inverter 20 is connected on the input side to the transformer 10 via a line 21 and on the output side to the coal cutter cable 9 via a line 22 leading to the terminal box 14.
6 Further details of the arrangement of Figure 1 are explained hereafter by reference to the block circuit diagram of Figure 2. A single motor 23 is assumed as the drive mechanism for the feed of the cutter-loader. The cutting drum motors are indicated by references 4 and 5 as in Figure 1. Signals h and i derived from the currents of these two motors are logged in the cutter-loader and transmitted separately via the data channel of the coal cutter cable to the regulating device in the parallel heading. In Figure 2 the transmission paths are indicated by two single lines 24 and 25.
In the heading station there initially occurs in a unit 26 a maximal selection, in that the greater operating current of the cutting drum motors 4 and 5 is determined at any time on the basis of the signals h and i. As a rule, one of the two cutting drum motors is loaded only slightly above idling. A signal is generated in a subsequent comparator 27 when it is ascertained that the current nominal value has been exceeded, and transmitted via an integral regulator 28 to a comparator 29, in which a subtraction of the predetermined nominal value signal c takes place. The resulting signal passes to the inverter 30, which controls the feed motor 23, so that the speed of the feed motor 23 is correspondingly reduced when it is ascertained that the nominal current of one cutting drum motor 4 or 5 has been exceeded.
The data transmission in the data channel of the coal cutter cable requires a relatively large dead time which is 7 dependent upon the type of power and transmission. With the regulation described heretofore, a reduction of the speed of the feed motor 23 might not therefore be induced sufficiently quickly in the event of a sudden overloading of the cutting drum motors 4 or 5. In order to bridge the dead time, a continuous logging of the total current of the two cutting drum motors 4 and 5 which can be measured in the parallel heading is additionally provided.
Furthermore, the signals h and i of the single currents are limited in units 31 and 32 in the heading station according to the nominal value of the motor currents, and a total signal is continuously formed from these signals in a totaller 33. This total signal and the signal n derived from the actual total current in the parallel heading are applied to a comparator 34. In the event of a sudden increase of the actual total current and also of the signal n, there occurs at the comparator 34 a resulting signal, which after amplification in an integral regulator 35, is compared in a further comparator 36 with the nominal value signal c, the resulting signal initiating an immediate reduction of the speed of the feed motor 23 by appropriate control of the inverter 30.
Figure 3 shows in the form of a block circuit diagram a circuit arrangement for carrying out the process without using a data channel. The same reference numbers as in the example of Figure 2 have been used for the cutting drum motors 4 and 5 and the feed motor 23.
In the heading station there is derived from the total 8 current of the cutting drum motors 4 and 5 a signal f proportional to the current, which together with the voltage u is applied to a known unit 37 for determining the reactance part of the total current. The reactance part ascertained and the total current f are applied to a logical unit 38, in which a continuous comparison of the amplitudes of total and reactance current is carried out. The power factor between the two currents is advantageously constantly determined. In the event of an overload of one of the two cutting drum motors 4 and 5, there occurs a noticeable variation of the ratio of total current to reactance current. If a predetermined limit value fails to be reached here, this produces a control signal at the output of the unit 38, which after amplification in a suitable regulating appliance 39, is conveyed as a control signal s to a comparator 40.
In the comparator 40 there occurs, in the same way as with the arrangement according to Figure 2, a subtraction of the aforementioned control signal s from the predetermined nominal value signal c. The resulting signal produces, via the frequency converter 30, a reduction in the speed of the feed motor 23 and, as a consequence of this, a withdrawal of the power of the overloaded cutting drum motor.
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