GB1591080A - Dc supply arrangement - Google Patents

Description

(54) A D.C. SUPPLY ARRANGEMENT (71) We, SIEMENS AKTIEN GESELLSGHAFT, a German company of Berlin and Munich, Germany (fed rep), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to an arrangement for the supply of direct current to intrinsically safe- installations in underground mining.

A known current supply arrangement for an output voltage of about 12V and an output current of 1A contains two constantly conductive control devices which are cast, together with a transformer which is on the input side and a rectifier connected to the latter on the output side, in a housing, which is in turn disposed in a housing of the "increased safety" kind of protection.

With the aid of series control devices (i.e.

control devices which are conductive continuously instead of having a switching effect) stabilised current supply arrangements have poor efficiency since the power loss in the transistors, through which the feed current flows, is released as heat and must be eliminated by cooling elements. Should larger fluctuations of the input voltage at the series control device have to be taken into account, the stabilisation must be dimensioned for the most unfavourable voltage and is thereby uneconomic.

Further devices for voltage control are known, which compare the voltage actual value alternately with an upper and a lower desired value according to the principle of the two-step controller. Should the actual value fall below the lower desired value, a switching transistor is driven so that the output voltage goes up. Should the upper desired value be exceeded, then the transistor is blocked. As a result of this operational method, the control losses are low. These devices are particularly suitable for the control of voltages for controls constructed from integrated switching circuits, therefore for voltage in the order of 5 V.

According to the present invention there is provided an arrangement for the supply of direct current to intrinsically safe installations in underground mining, comprising a transformer with at least one rectifier connected at the output side, and an assembly carrier carrying an assembly in or on which are mounted, to operate on output electricity from said at least one rectifier, a first electricity control device which is operable according to a switching principle, a second electricity control device which is arranged to operate continuously conductively for controlling current and voltage and is connected in series with the first electricity control device, an over voltage protection device and an under voltage protection device.

According to one embodiment, as a result of the use of a switching electricity control device in conjunction with a series (ie continuously conductive) control device, the arrangement operates with low losses. The input voltage of the arrangement can thereby diverge from its nominal value by + 30 /O.

The output voltage of the assembly can amount, for example, to 12 V in the case of 1.5 A or to 5 V in the case of 6A.

For a better understanding of the invention and to show how it may be put into effect reference will now be made by way of example, to the accompanying drawings in which: Figure 1 is a circuit diagram; Figure 2 is a view of an assembly; and Figures 3 to 5 show parts of a flameproof unit.

An alternating current transformer (Figure 1) feeds a switching controller (regulator) 3 and a series (ie continuously conductive) controller (regulator) 4 controlling current and voltage via a rectifier bridge 2. The switching controller 3 includes a control part 5 which controls the pulse-pause ratio of a switching transistor 6 in such a way that a direct voltage of basically constant level is produced at the output of the controller - after smoothing the pulsating direct current by means of a choke 7 which is charged during the duration of connection of the switching transistor 6 and is discharged during the blocking time, and by means of a capacitor 8. The charge current flows via a diode 9 in the blocking state of the transistor 6, which is periodically switched on and off by the control part 5.In order to attain an output voltage in the order of 5 V, the uncontrolled voltage at the output of the switching controller can amount to for example 24 V direct voltage. The series controller 4 is connected to the output of the switching controller 3. It comprises a constantly conductive control transistor 10 and a control part 11 constructed from integrated switching circuits. As a result of prestabilisation by the switching controller 3, the heat loss occurring at the transistor 10 is low.

By virtue of the low power loss occurring at the control transistor, the arrangement, which is advantageously combined into an assembly, is suitable to be inserted into a housing which is resistant to compression.

Instead of this, the assembly can be embedded in a sealing compound.

A voltage proportional to the output current is compared with a reference voltage by means of a measurement device consisting of a resistance 12 and an amplifier 13. Should the output current exceed the nominal current, the control part 5 and the control part 11 are blocked. The two measurement devices operate independently of one another and effect, if necessary, a switching off of the output current.

A thyristor 14 is connected to the output of the series controller as an over voltage protector whose control electrode is positioned on a voltage divider formed from resistances 15, 16 and which short-circuits the output in the case of an over voltage. An operational amplifier 17 is disposed in parallel with this in order to supervise under voltage and compares the output voltage with a specified reference voltage of for example 3.5 V. Should the output voltage fall below this value, the control part 5 is blocked, so that the latter supplies no more current. In order to lift the controller block, the total arrangement must be switched off for a few seconds.

The described supervisory devices guarantee that the mechanism does not supply a current that is higher than the nominal current and that the voltage does not exceed or fall below the specified upper or lower limit values. The current supply arrangement is protected from sustained short-circuits. Since the output capacity of the arrangement is low, the current peak is limited to a minimum in the case of a short-circuit.

Figure 2 shows a side view of an assembly 18 containing the switching controller 3 and the series controller 4 including the measurement devices 12, 13, the operational amplifier 17 and the over voltage protection arrangement 14, 15, 16. In this view of the constructional elements only the thyristor 14 and the diode 9 can be seen, which are attached to a common cooling element 19 which is also for the transistors 6 and 10, whereas the remaining constructional elements are disposed on a printed circuit board 20 and are embedded in a sealing compound 21. The cooling element 19 is connected to the printed circuit board by means of distance bolts 22.Moreover, a carrier frame 23 is attached to the printed circuit board by means of distance pieces and a front plate 25 is attached by a pulling grip 26 to the printed circuit board, to whose lower end a terminal strip 27 with, for example, fifteen poles is attached.

In Figures 3 and 4, a current supply system is shown as the example of the embodiment consisting of several assemblies including an input transformer and a rectifier, the system being inserted in a flameproof housing 28, 29.

A terminal box 30 of the "increased safety" kind of protection is attached to the base of the housing 28 on the input side. A duct 31 for connecting the transformer 32 to the mains is inserted into the adjoining walls of the terminal box and of the base of the housing. The connection leads not shown from the duct to the transformer are conducted via a disconnection switch 33, whose drive axis 34 is for example connected to a switching axis 36, conducted through the housing cover 29, by means of a plug coupling 35. The appertaining handle 37 is formed with a recess which frees the access to a locking device 38 of the cover in the open position of the disconnection switch. In order to attach rectifier constructional elements 43 and the assemblies 18, for example three frames 39 are supported by separator bolts 40 in the base of the housing.

Ribbed guides 41 placed on each other in pairs are engaged into the frames.

As Figure 5 shows to a greater extent, the ribbed guides 41 are provided with a longitudinal groove 42 which serves to conduct the printed circuit board 20 of the constructional elements 43 or assemblies 18. Socket strips 44 are assigned in the under side of the housing to the terminal strips 27 provided on the assemblies 18 and likewise the constructional elements 43, the individual sockets of these socket strips being connected to contacts of a contact strip 45 attached for example on the middle frame 39 or of a further contact strip 46 disposed for example in the base of the housing. The contacts of these strips are connected to multi-pole ducts 47 which are inserted in the adjoining walls of the under side of the housing and of a further terminal box 48 attached to the latter. The terminal ends of the ducts 47 are connected to connector sockets of additional housing 51 via control lights, in particular light diodes 50, disposed on a further printed circuit board 49; the socket housing can be inserted into the additional housing 52 by means of corresponding plug inserts. According to Figure 4, which shows the supply system in a top view, there are provided for example two rectifier constructional elements characterised by the circled reference numbers 43, two assemblies for 5 V, 6 A likewise characterised by circled reference numbers 18, and three inserted assemblies 18 for 12 V, 1.5 A are shown.

The described and illustrated arrangement provides an arrangement for the current supply of intrinsically safe, integrated control devices containing switching circuits, which works with very slight losses, which can be connected on the input side to voltages of different value and which, because of its constructional shape, is suitable for the construction of current supply systems. The fact that the arrangement works with slight losses is due to the series connection of the switching controller 3 and the series controller 4. The losses of the switching controller 3 are slight, and the input voltage of the series controller 4 prestabilised by the switching controller 3 also reduces its power loss.

In an embodiment which is not illustrated, the flameproof unit can be formed by embedding at least one assembly 18 and the transformer 32 and at least one rectifier 43 in a sealing compound.

Also, the flameproof unit may consist of several individually sealing-compound-cast assemblies and likewise cast constructional elements containing the transformer and the rectifier.

WHAT WE CLAIM IS: 1. An arrangement for the supply of direct current to intrinsically safe installations in underground mining, comprising a transformer with at least one rectifier connected at the output side, and an assembly carrier carrying an assembly in or on which are mounted, to operate an output electricity from said at least one rectifier, a first electricity control device which is operable according to a switching principle, a second electricity control device which is arranged to operate continuously conductively for controlling current and voltage and is connected in series with the first electricity control device, an over voltage protection device and an under voltage protection device.

2. An arrangement according to claim 1, wherein a plurality of such assemblies with equal or different output voltages and currents, and the transformer and the at least one rectifier, are assembled into a flameproof unit.

3. An arrangement according to claim 2, wherein the flameproof unit is formed by providing the assembly carrier or carriers carrying the assembly or assemblies, the transformer and the at least one rectifier in a pressure-resistant housing.

4. An arrangement according to claim 2, wherein the flameproof unit is formed by embedding at least one assembly and the transformer and the at least one rectifier in a sealing compound.

5. An arrangement according to claim 2, wherein the flameproof unit consists of several individually sealing-compound-cast assemblies and likewise-cast constructional elements containing the transformer and the at least one rectifier.

6. An arrangement for the supply of direct current to intrinsically safe installations in underground mining, the arrangement being substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. there are provided for example two rectifier constructional elements characterised by the circled reference numbers 43, two assemblies for 5 V, 6 A likewise characterised by circled reference numbers 18, and three inserted assemblies 18 for 12 V, 1.5 A are shown. The described and illustrated arrangement provides an arrangement for the current supply of intrinsically safe, integrated control devices containing switching circuits, which works with very slight losses, which can be connected on the input side to voltages of different value and which, because of its constructional shape, is suitable for the construction of current supply systems. The fact that the arrangement works with slight losses is due to the series connection of the switching controller 3 and the series controller 4. The losses of the switching controller 3 are slight, and the input voltage of the series controller 4 prestabilised by the switching controller 3 also reduces its power loss. In an embodiment which is not illustrated, the flameproof unit can be formed by embedding at least one assembly 18 and the transformer 32 and at least one rectifier 43 in a sealing compound. Also, the flameproof unit may consist of several individually sealing-compound-cast assemblies and likewise cast constructional elements containing the transformer and the rectifier. WHAT WE CLAIM IS:

1. An arrangement for the supply of direct current to intrinsically safe installations in underground mining, comprising a transformer with at least one rectifier connected at the output side, and an assembly carrier carrying an assembly in or on which are mounted, to operate an output electricity from said at least one rectifier, a first electricity control device which is operable according to a switching principle, a second electricity control device which is arranged to operate continuously conductively for controlling current and voltage and is connected in series with the first electricity control device, an over voltage protection device and an under voltage protection device.

2. An arrangement according to claim 1, wherein a plurality of such assemblies with equal or different output voltages and currents, and the transformer and the at least one rectifier, are assembled into a flameproof unit.

3. An arrangement according to claim 2, wherein the flameproof unit is formed by providing the assembly carrier or carriers carrying the assembly or assemblies, the transformer and the at least one rectifier in a pressure-resistant housing.

4. An arrangement according to claim 2, wherein the flameproof unit is formed by embedding at least one assembly and the transformer and the at least one rectifier in a sealing compound.

5. An arrangement according to claim 2, wherein the flameproof unit consists of several individually sealing-compound-cast assemblies and likewise-cast constructional elements containing the transformer and the at least one rectifier.

6. An arrangement for the supply of direct current to intrinsically safe installations in underground mining, the arrangement being substantially as hereinbefore described with reference to the accompanying drawings.