GB2216274A - Apparatus for ascertaining the direction of rotation of the phases of a three-phase electric network - Google Patents

Description

22-16274 "APPARATUS FOR ASCERTAINING THE DIRECTION OF ROTATION OF THE

PHASES OF A THREE-PHASE ELECTRIC NETWORK" The invention relates to apparatus for ascertaining the direction 5 of rotation of the phases of a three-phase electric network.

Precautions must be taken prior to making any connection to a three-phase electric network.

For example, if it is a rotating machine such as a pump or a saw which is involved, then to ensure satisfactory operation it is necessary, to avoid an incident or accident, that the connection of the phases between the network and the rotary machine respect a given configuration linked with their rotation and it is therefore important to know beforehand the direction of this rotation.

Precautions of the same kind should be taken when connecting two three-phase electric networks together, as otherwise there may be a short circuit across at least some of their phases.

Apparatus is currently available for recognising the direction of rotation to be observed.

Generally such apparatus employs indicating means, in practice these are warning lights, the actuation of which follows one or other of the directions of rotation of the phases of the electric network to be monitored.

The present invention relates more particularly to those of such apparatus which comprises a plurality of indicating means which, operated by a control circuit to energise them in sequence to indicate the direction of rotation which is to be recognised, are disposed according to a circumference along which they are regularly distributed, the whole forming what is usually referred to as a caterpillar'.

In practice, the control circuit which operates these indicating means, hereinafter referred to as sequentially controlled indicating means, comprises possibly in integrated form a counter which receives at one of its inputs the pulses from a clock, and a decoder, the outputs of which are suitably connected to the sequentially controlled indicating means.

Devices of this kind have performed satisfactorily.

2 According to the invention there is provided apparatus for ascertaining the direction of rotation of the phases of a three-phase electric network, comprising-a plurality of indicating means operated by a control circuit to energise them in sequence according to the image of the direction of phase rotation to be recognised, hereinafter for convenience referred to as sequential control indicating means, the control circuit comprising a counter which receives at one of its inputs the pulses of a clock, and a decoder, the outputs of which are suitably connected to the sequential control indicating means, wherein the sequential control indicating means used are indicating means which have effects which differ according to the direction of the current which passes through them, the corresponding control circuit comprises in parallel two decoders, one for the supply of the indicating means in one direction, the other to supply the indicating means in the opposite direction, the control circuit comprising in addition an orientation circuit which is sensitive to the direction of rotation of the phases in the network in question and operates one or other of the decoders according to the direction of rotation.

Such apparatus can have improved convenience of use and performance.

Hitherto the sequentially controlled indicating means which constitute the 'caterpillar', always traversed by their energising current in the same direction, operate in the same way for one direction of rotation or the other, the recognition of this direction of rotation resulting solely from the sequence, in one direction or tIne other, in which they are thus successively energised.

Thus, these sequentially controlled indicating means function differently according to the direction of rotation of the phases.

For example, there are bi-chromatic diodes which light up green for one of the directions of rotation, that which is assumed to be the correct direction, and show red for the opposite direction of rotation, that which is assumed to be incorrect.

The direction of phase rotation to be recognised can thus be more clearly visualised, while the colours used, one representing approval, the other rejection, advantageously directly indicate whether the envisaged connection is suitable or whether, on the other hand, it should be remade.

3 In the prior art devices, furthermore, recognition of the direction of rotation of the phases normally involves these phases being compared by the dephasing of one of them by a dephasing circuit of suitable resistance and capacitance.

But such an arrangement has the drawback of lacking flexibility with regard to the applications which can be envisaged in so far as, for its constitution, the dephasing circuit to be used depends largely on the frequency on the alternating signals of the phases to be detected, and upon their amplitude.

Preferably, the orientation circuit employed comprises two flip-flops mounted in cascade, one to the inputs of which are applied the signals delivered by two shunting circuits each of which respectively receives two of the phases of the network in question, and the other to the inputs of which are applied not only the output from the precedent flip-flop but also the signals delivered by a shunting circuit which receives the third phase of the network.

Thus, by the substitution of an electronic artifice for a conventional dephasing circuit, the apparatus of the invention can be suitable for recognising the direction of rotation of the phases of a three-phase electric network whatever the frequency and amplitude of the alternating signals of these phases.

However, it can easily happen, when the direction of rotation of the phases is recognised, that despite an incident on any one of the phases, for example the breakage of a phase or an undesired connection to neutral or to earth, the sequential control detecting means will be functioning normally without any intervention and without giving cause to suspect the existence of such a fault.

In order to offset this disadvantage, the device may have in addition to its sequential control indicating means, another indicating means hereinafter referred to as the fixed control indicating means, the supply to which is controlled by a level detector which receives a voltage representing the sum of the voltages of the three phases of the network.

Thus, if one of the phases is defective, this fixed control indicating means which is for example as previously a warning light will operate permanently.

4 Preferably, the level detector which controls it also controls the associated clock so that when this latter is blocked, energising of the sequential control indicating means is also interrupted, which advantageously reinforces the resultant indication of the defect which 5 is present in one of the phases.

Therefore, it is sufficient to monitor each of these.

The apparatus can thus make it possible without ambiguity to recognise the direction of rotation of the phases in a three-phase electric network independently of the frequency of the network and signal the presence of a possible fault in connection on one of these phases.

The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:- Figure 1 is a circuit diagram of apparatus for ascertaining the direction of phase rotation of the phases of a three-phase electric network according to the invention; Figure 2 is an electronic diagram appropriate to an embodiment of the apparatus of Figure 1; Figures 3A to 3B are traces illustrating one of the functions of the apparatus of Figure 1; Figures 4A and 4B are similarly traces iiustrating another of the functions of the apparatus of Figure 1; and Figure 5 is a partial plan view of the apparatus of Figure 1 illustrating a preferred arrangement for the various indicating means which it comprises.

Generally, and as illustrated in the drawings, apparatus for ascertaining the direction of phase rotation comprises three terminals 10A, 10B, 10C suitable for connection to three phases A, B, C of a three-phase electric network, the direction of phase rotation of which _30 is to be ascertained.

A plurality of indicating means 11, referred to hereinafter as sequential control indicating means, are operated by a control circuit 12 which can energise them in sequence in the image of the direction of phase rotation to be ascertained. The control circuit 12 generally comprises a counter 13 which receives at one of its inputs the pulses from a clock 14, and a decoder 15, the outputs of which are suitably connected to the sequential control indicating means 11.

In the embodiment shown, the sequential control indicating means 11 are five in number.

< Preferably, the number of outputs of the corresponding decoder 15 is a multiple of this number so that it is possible to benefit from a "flash" effect to energise the sequential control indicating means 11.

For example, the decoder 15 comprises for this purpose ten outputs and they are only used for energising sequential control indicating means 11 at the rate of one in two.

In practice, in the embodiment shown, the counter 13 and the decoder 15 are integrated, so that they together form one single and the same component 16.

This is for instance a Johnson counter.

The sequential control indicating means 11 used are indicating means of which the effects are differentiated according to the direction of the current passing through them and the corresponding control circuit 12 comprises in parallel two decoders 15, 15', of which one, for example the decoder 15, supplies the sequential control indicating means 11 in one direction and the other, the decoder 151, supplies them in the opposite direction, the control circuit 12 furthermore comprising, as detailed hereinafter, an orientation circuit 17 which is sensitive to the direction of rotation of the phases of the network in question and can operate one or other of the decoders 15, 15' according to the direction of rotation.

In practice, in the embodiment illustrated, the decoder 15' is identical to the decoder 15.

Therefore, like the latter, it belongs to a Johnson counter 161.

Thus, in this embodiment, there are two working counters 13, 13'.

A.single counter 13 or 13' would however be sufficient to serve the two decoders 15, 151 needed.

Preferably, and as illustrated in the electronic diagram in Figure 2, the sequential control indicating means 11 used are bi-chromatic diodes.

In other words, they are two-colour electroluminescent diodes and each 1s for example formed by two crystals disposed head-to-tail in one and the same housing.

For example, these two-coloured diodes can light up green when traversed by the current in one direction and red when traversed by the 6 current in the opposite direction.

For the supply, through the decoders 15, 15', of the sequential control indicating means 11 which are thus constituted, the control L_ circuit 12 in the embodiment illustrated comprises a three-phase 5 rectifier bridge 18.

For each of the phases A, B, C upstream, the three-phase rectifier bridge 18 in practice comprises current limiting resistors 19A, 20A; 19B, 20B and 19C, 20C, as shown in Figure 2, a double-alternating rectifier circuit 21A, 21B, 21C formed of two diodes 22, and it delivers its direct current output voltage to a filtering capacitor 23 of which the terminal potential, applied to the input of the counters 13, 13' is duly limited, to 10 volts for example, by a Zener diode 24. For the necessary current amplification, there are between the 15 outputs of the decoders 15, 151 and the sequential control indicating means 11, buffers 25, 25' with, connected in series with them, on the side of the decoder 15, current limiting resistors 26. In a manner known per se, the clock 14 which provides for joint control of the counters 13, 13', is a blocked oscillator. 20 As such an oscillator is well known in itself, it wLL- not be described in detail here. The orientation circuit 17 comprises a cascade arrangement; o!-;qo electronic type RS flip-flops 28, 29 comprising NO-OR gates. To the inputs of the flip-flop 28, are applied the signals delivered by two shunting circuits 30A, 30C each of which respectively receives two of the phases, such as phases A, C, while to the inputs of the flip-flop 29 are applied not only the output from the preceding flip- flop 28 but also the signals delivered by a shunting circuit 30B receiving the third phase, in this case phase B. 30 For each of the phases A, B, C, the shunting circuit 30A, 30B, 30C thus employed, which operates downstream of the corresponding current limiting resistors 19A- 20A, 19B-20B, 19C-20C, comprises a capacitor 31, a resistor 32 and two protective diodes 33, 34. The output from the flip-flop 29 is applied to an integrating network 35 comprising in addition to an orientation diode 36, a capacitor 37 and a resistor 38 and, at the output of this integrating circuit 35, in order to operate either the Johnson counter 16, or the 7 -ion or the Johnson counter 161 and therefore, for control in one direct other, there are sequential control indicating means 11, a reversing Schmitt trigger 40, followed by an inverter 41 upstream of the sole Johnson counter 161.

In addition to the sequential control indicating means 11, the apparatus comprises another indicating means 43, hereinafter referred to as the fixed control indicating means.

The fixed control indicating means 43 is preferably a warning light.

As shown in Figure 2, it may for example be a simple electroluminescent diode.

The supply to it is controlled by a level detector 44, which is in practice an inverting Schmitt trigger receiving a voltage which reflects the sum of the voltages of the three phases A, B, C.

To do this, there is provided for each phase A, B, C, a single-alternating rectifier circuit 45A, 45B, 45C, which in practice comprises a simple diode 46, and this rectifier circuit 45A, 45B, 45C is, for each phase A, B, C, followed by a current limiter resistor 47, all the current limiting resistors 47 thus used forming with two other resistors 49, 50 a potentiometer bridge 48 at the input of the inverting Schmitt trigger 44.

In addition to the fixed control indicating means 43, the inverting Schmitt trigger 44 operates, in parallel in respect of this fixed control indicating means 43, the clock 14 for the possible inhibition thereof and therefore for inhibiting the buffers 25, 25'.

In practice, this inverting Schmitt trigger 44 operates through an integrating circuit 52 comprising not only an orientation diode 53 but also a condenser and a resistor 55 and an inverter 56 with an orientation diode 57 upstream of the clock 14.

Preferably, and as shown in Figure 5, the sequential control indicating means 11 are regularly distributed over a circumference centred on the fixed control indicating means 43.

The various components mentioned hereinabove have their own power supply.

As this will be familiar to a man skilled in the art, it has not been illustrated in the drawings and will not be described here.

8 Once the apparatus has been connected to the network of which it is intended to ascertain the direction of phase rotation, by connection of each of its terminals 10A, _10B, 10C to the corresponding phase A, B, 41 C of this network, the oscillator constituting the clock 14 comes into operation and continuously delivers pulses to one and the other of the Johnson counters 16, 16' and the outputs of these, decoded for the purpose, only become conductive in turn, with a subsequent offset from one to the other at each of the clock pulses which they receive.

The supply voltage delivered by the double alternating rectifier circuits 21A, 21B, 21C therefore only arrives cyclically through the Johnson counter 16 or the Johnson counter 161 and in a specific sequence, at the sequential control indicating means 11.

The arrangement is that the corresponding sequence corresponds to the location of these sequential control indicating means 11 along the circumference along which they are established, so that the corresponding excitation, visualised by the fact that they light up, seems to pass in one direction or the other according to the arrow F or the arrow P in Figure 5.

When for example the sequential control indicating means 11 are supplied by the Johnson counter 16 and when they are traversed by the current in a first direction, these sequential control indicating means 11 light up for example in a green colour, and their lignting sequence corresponds to a circular path of the corresponding excitation which, as indicated by the arrow F in Figure 5, is a clockwise direction.

When, in contrast, the sequential control operating means 11 are supplied through the Johnson counter 161 and when consequently they are traversed by the current in an opposite direction to that previously indicated, the sequential control indicating means 11 light up for example in a red colour and their illumination sequence corresponds to a circular path of the corresponding excitation which, as indicated by the arrow F1 in Figure 5, duly differentiated from the previously mentioned arrow F is then the trigonometric direction or anti-clockwise direction which is opposite to the previously mentioned clockwise direction.

In order to determine which of the Johnson counters 16, 16, through which the supply is to pass to the sequential control indicating means 11, the orientation circuit 17 proceeds as follows.

9 As indicated by the traces in Figures 3A and 3B, the phases A, B, C permanently deliver sinusoidal and alternating waves 60A, 60B, 60C which are offset by 1200 in respect of one another, and the shunting circuits 30A, 30B, 30C correspondingly and as they pass through zero, in increasing phase of these waves, deliver pulses 61A, 61B, 61c which are_ also offset by 1200 in respect of one another.

It is the order of succession of these pulses which determines the direction of rotation of the phases A, B, C in question.

Let it be first of all assumed, as in Figure 3A, that the pulses 61B linked to the phase B exactly follow by 1200 those 61A which are connected to the phase A and they are themselves exactly followed by 1200 by the pulses 61C connected to the phase C.

At the logic level 1, each pulse 61A positions the flip-flop 28 and each pulse 61C restores it to logic level 0.

Thus, a peak 63 is created cyclically at the output 62 of the flip-flop 24.

The pulse 61B linked to the phase B is compared by the flip-flop 29 which this peak 63 which is applied to one of the inputs of the flip-flop 29.

If, as is the case in the trace in Figure 3A and which corresponds to a correct rotation of the phases A, B, C, that is to say a rotation of these phases in the order corresponding to their rank, firstly A, then B and finally C, the pulse 61B is then present even when the peak 63 is jointly present, the output 64 of the flip-flop 29 permanently remains at the logic level 0, as shown diagrammatically by a continuous line 65 in this diagram.

In this case, it is the Johnson counter 16 which is operative, while the Johnson counter 161 is inhibited by the inverter 41.

If, one the other hand, as shown in the trace in Figure 3B, the pulse 61B linked to the phase B is outside the peak 63 created by the flip-flop 28, which corresponds to an incorrect direction of rotation of the phases A, B, C, the phase C occurring before the phase B, the output 64 of the flip-flop 29 alternatively passes through the logic level 0 to the logic level 1, thus with the creation of a peak 66 which is offset in relation to the preceding peak 63.

The peaks 66 then present at the output of the flip-flop 29, at a frequency equal to that of the network in question, are memorised by the integrating circuit 35 and the inverting Schmitt trigger 40 disposed downstream thereof then produces inhibition of the Johnson counter 16 while the Johnson counter 161 comes into operation in turn, having been released by the inverter 41. 5 In the foregoing, it has been assumed that in accordance with the trace in Figure 4A, which gives the level of voltage at the input terminal of the inverting Schmitt trigger 44, the various phases A, B, C were all correctly connected. Let N1 be the mean level of this voltage, which results from 1.0 addition of the semi -alternations of the sinusoidal waves 60A, 60B, 6oc.

The inverting Schmitt trigger 44 is so chosen that, for this level N1, the fixed control indicating member 43 is not energised.

If, now, it is assumed that one of the phases, for example phase B, is incorrectly connected, being for example connected to neutral or to earth, then the amplitude of its wave 60B is consequently reduced, or even cancelled out if it is broken.

The mean level N2 of the voltage then applied to the input terminal of the inverting Schmitt trigger 44 is itself consequently reduced.

In fact, for this level N2, the inverting Schmitt trigger 44 via the integrating circuit 52, produces energising of the fixed control indicating means 43 which then lights up permanently.

At the same time, this inverting Schmitt trigger 44 causes inhibition of the oscillator constituting the clock 14 and hence that of the buffers 25, 25' so that as the sequential control indicating means 11 are no longer energised, only the fixed control indicating means 43 is energised.

At this moment, it is easy to identify the phase or more 30 generally the input A, B, C which is defective.

In fact, it is sufficient to disconnect the terminals 10A, 10B and 10C one after the other.

That terminal the disconnection of which does not change the indications is the faulty input.

The invention is not confined to the embodiment which has been described and illustrated and alternative embodiments are possible within the scope of the appended claims.

In particular, the indicating means used need not necessarily be warning lights; on the contrary, acoustic means may equally well be used as substitutes for the said warning lights, or they may be used in association therewith.

More generally, each of the components more particularly described may be replaced by another component which is capable of carrying out the same function.

11 4 12

Claims (9)

1 Apparatus for ascertaining the direction of rotation of the phases of a three-phase electric network, comprising a plurality of indicating means operated by a control circuit to energise them i n sequence according to the image of the direction of phase rotation to be recognised, hereinafter for convenience referred to as sequential control indicating means, the control circuit comprising a counter which receives at one of its inputs the pulses of a clock, and a decoder, the outputs of which are suitably connected to the sequential control indicating means, wherein the sequential control indicating means used are indicating means which have effects which differ according to the direction of the current which passes through them, the corresponding control circuit comprises in parallel two decoders, one for the supply of the indicating means in one direction, the other to supply the indicating means in the. opposite direction, the control circuit comprising in addition an orientation circuit which is sensitive to the direction of rotation of the phases in the network in question and operates one or other of the decoders according to the direction of rotation.

2. Apparatus according to claim 1, wherein the sequential control indicating means used are bi-chromatic diodes.

3. Apparatus according to claim 1 or claim 2, wherein the orientation circuit comprises a cascade arrangement of two flip-flops, one to the inputs of which are applied the signals delivered by two shunting circuits each respectively receiving two of the phases of the network and the other to the inputs of which are applied, in addition to the output from the preceding flip-flop, signals delivered by a shunting circuit receiving the third phase of the network.

4. Apparatus according to any one of claims 1 to 3, wherein to supply the sequential control indicating means through decoders, the control circuit comprises a three-phase rectifier bridge.

13

5. Apparatus according to any one of claims ' to 4, wherein the number of outputs of the decoders is a multip-e of the num6er of sequential control indicating means to be controlled.

6. Apparatus according to any one of claims 1 to 5, wherein comprising in addition to the sequential control indicating means, another indicating means, hereinafter referred to for convenience as the fixed control indicating means, the supply to which is controlled ng a voltage which by a level detector, the level detector receiv represents the sum of the voltages of the three phases of the network.

7. Apparatus according to claim 6, wherein in parallel in respect of the fixed control indicating means, the levell detector likewise controls the clock.

8. Apparatus according to claim 6 or claim 7, wherein the sequential control indicating means are regularly distributed over a circumference.

9. Apparatus for ascerraining the direction of rotatLon of the phases of a three-phase electric network substantially as hereinbefore described and illustrated with reference to the accompanying drawings.

Published 1989 at The Patent Office, State House, 68"? 1 High H01born, London WCIR 4TP. Further copies maybe obtained from The Patent Office Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques Itd, St Mw7 Cray, Kent, Con. 1/87