CA1263144A

CA1263144A - Relay trouble detecting device

Info

Publication number: CA1263144A
Application number: CA000483039A
Authority: CA
Inventors: Heihachiro Umemura
Original assignee: SHINKOH ELECTRIC CO Ltd
Current assignee: SHINKOH ELECTRIC CO Ltd
Priority date: 1984-06-04
Filing date: 1985-06-03
Publication date: 1989-11-21
Also published as: FR2565430A1; DE3520257A1; GB2162391A; DE3520257C2; GB2162391B; GB8513905D0; FR2565430B1

Abstract

ABSTRACT OF THE DISCLOSURE
A relay trouble detecting device which at the outbreak of any trouble in a relay (including a magnet switch) detects such trouble immediately and gives an alarm. This device is provided with a sensor for detecting driving current arranged at a driving circuit for a load and a judging circuit to which signals from the sensor and operation signals from a relay operation circuit are input.
the judging circuit stores the value of mutual relation between the two signals in normal condition and works an alarm circuit when the mutual relation between the two signals shows the value outside the standard.

Description

i3~4 This invention relates to a relay trouble detecting device, which automatically detects any trouble in a relay or magnet swltch (hereinafter referred to simply as "relay") pro-vided in a driving circuit for a motor or other load.

High-voltage, high current is used for driving a motor for a large hoist crane or processing machine. It is dangerous to carry out a switching operation manually for starting and stopping. In order to avoid such danger, relays which open and close a driving circuit of high-voltage, high current from a low voltage, low current are employed. The life of the relay depends upon the fre~uency of use, values of voltage and current, etc.
Especially in the case o a three-phase alternating circuit, when any one of the three phases has a bad connection, so-called single-phase running occurs. This can result in burning of the motor. Where relay contacts become fused together, so-called "runaway" occurs and does great damage to persons and ob;ects.
With this in view, it is customary to set the permissible time for use of each relay and to replace the relays by new ones when the permissible time has expired. This, however, involves uneco-nomical use of relays bacause some are still usable safely at the time of change. Depending upon the environment in which the relays were used, some break down earlier than usual due to gas, water c~ntent, etc. Th~s, a safe countermeasure has heen desired.

According to the present invention there is provided a relay trouble detecting device, comprising: a sensor for generat-ing detection signals in response to driving current flowing in a driving circuit; means for generating relay operation signals in response to operatlon o a relay associated within said driving circuit; and a judging circuit for examining said detection sig-nals and said relay operation signals to determine whether a fault condition exists, said judging circuit selectively produc-ing a signal to activate an alarm circuit upon detectlon of afault condition.

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The invention wilJ. now be described in more detail, by way of example only, with refe.rence to the accompanying drawings, in which:-Fig. 1 is a schematic drawing illustrating the baslc concept of the present invention;

Fig. 2 is a perspective view of the sensor for detect-ing driving current;

Fig. 3 is a perspective view of another embodiment of a sensor for detecting driving current;

Fig. 4 is an overall circuit diagram showing the first embodiment of the present invention;
Fig. 5 is an overall circuit diagram showing the second embodiment of the present invention;

Fig. 6 is an overall circuit diagram showing the third embodiment of the present invention;

Fig. 7 and Fig. 8 relate to the fourth embodiment of the present invention, in which Fiy., 7 is an overall circuit diagram and Fig. 8 is a plan view of the main device from which an upper lid was removed; and Fig. 9 is an overall circuit diagram of the fifth embodiment o~ the present invention.

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Fig. 1 is a drawing showing the basic concept relay trouble detecting device according to the present invention. In Fig. 1, a power source 1 is connected to a load 3, such as a motor, via a relay 4. The relay 4 is opened and closed by a relay operating circuit 5. Numeral 6 denotes a rPlay trouble detecting ~5 : ' ... .

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device which comprises a sensor 7 for detectiny dr~ving current disposed in a driving circuit 2 and a ~udging circuit 8 to which detec-ting signals from said sensor 7 and operating slgnals from the operating circuit 5 are applied. As the means oE inputting operating signals, a sensor 9 for detecting operating signals is fitted to the operating circuit 5, for example. The judging cir-cuit 8 is composed of an IC for example. This circuit compares the relay operating signals with the detecting signals from the sensor for detecting driving current and in the case of three-phase alternating current, it detects whether or not electriccurrent of each phase is uniform and thus judges whether the relay 4 is good or bad. When an abnormality occurs, an alarm circuit 10 is actuated -to give an alarm or a switch 12 for cutoff provided in the driving circuit 2 is opera-ted to open the driving circuit 2.

LP is an alarm lamp. The sensor 7 for detecting driv-ing current is composed of a current transformer, for example, and is so constructed that it detects electric current of each phase separately in the case where the power source is three-phase AC. An example is shown in Fig. 2. In a sensor 15 for detecting driving current shown in Fig. 2, conductors Ra, Sa, Ta, connected to each phase R, S, T, respectively, are wound round a winding 16 (in the drawing conductors are shown passing through Ra~ so as to generate induced ~2~3~

current at the wlnding 1~. The number of turns of each phase is different. Numeral 17 is an output terminal whlch is connecked to the judging circuit 8. The ~udging circuit 8 compares induced current induced at the winding 16 of each phase and detects any variation of induced current caused by interruption or bad con duction of any one of the three phases.

Fig. 3 shows a different type of sensor for detecting driving current. This type is applicable to the case where each conductor of the driving circuit 2 is thick and is unsuitable for winding round the winding 16 as shown in Fig. 2. A sensor 20 for detecting driving cuxrent comprises current transformers ~la,21b provided for conductors R, S, T (a current transformer for R
phase is omitted in the drawing) for detecting each phase and a main current transformer 24. Conductors 23a,23b are wound round a winding 25 of the main current transformer 24 from the sec-ondary sides of the current transformers 21a,21b for detecting each phase. As will be described later, it is possible to have the current transformers 21a~21b for detecting each phase serve as a sensor for detecting drivlng current. Output signals of each transformer are applied to a ~udging circuit via a conver-sion circuit.

The sensor 9 for detecting operation signals is com-posed of a current transformer, for example, and "
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detects electric current flowing in the relay operating clrcult 5when the circuit 5 is working. However, in the case where the operating circuit 5 is DC, operating signals are applied to the ~udging circuit 8 by other proper means as will be described later.

Embodiment 1 The first embodiment 1 is shown in Fig. 4~ In a three-phase driving circuit 30, a plurality ~three, for example) of loads 31a,31b and 31c are arranged in parallel. Each load is a driving motor, for example, and for normal and reverse operation of the driving motor, each load is connected to the driving cir-cuit 30 via the relays 32a,32b,32c ....... 32f. Numeral 33 is a relay operating circuit which is provided with solenold coils MCl,MC2,MC3 .. ~... MC6 for relays 32a,32b,32c ..... , respectively and interlock type push buttons Pb2,Pb3,Pb4 for the solenoid coils. The push button Pbl is a main push button.

A relay trouble detecting device 40 comprises a sensor 41 for detectlng driving current provided in the driving circuit 30 and an operating box 42. The operating box ~2 is provided with a sensor 43 for detecting operation signals for the relay operating circuit 33 and a switching contact 45 for a judging circuit 44 and an alarm circuit 46. The alarm circuit 46 is con-nected ~o a no ~use breaker ~hereina~ter referred to as NFB ) hav-ing a trip circuit provided in the driving circuit 30. Both the sensor 41 Eor detecting driving curr~nt and the sensor 43 for detecting operation signals are composed of current transformers.
The sensor 41 should prefer~bly be constructed as shown in Fig. 2 or Fig. 3. In Fig. 4, 48a,48b .~.... 48f are normally closed contacts for prevent1ng erroneous operation and are opened when the solenoid coils MC2,MCl,MC4 ...... operate.

In the above constructlon, when the relays 32a,32b ..... ~ are in normal condition~ loads 31a,31b,31c are driven by ' ~ ` :

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input of relays and the amount of electric current flowlng in the driving circuit 30 is detec-ted by the sensor 41 for detecting driving current. In this case, according to the horsepower of the load and the number of loads, the amount of electric current flowing in the driving circuit 30 should vary but the amount of alternating current in each of the three phases is uniform. By pressing the push buttons Pb2,Pb3,Pb~ to work the relays 32a,32b ...... , the amount of electric current flowing in thP relay oper-ating circuit 33 is detected by the sensor 43 for detecting oper-ation signals. In this case, the amount of electric current flowing in the operation circuit 33 is proportionate to the num-ber of closed push buttons.

The judging circuit 4~ can find the number of closed push buttons from the amount of electric current induced at the sensor 43 for detecting operation signals. When, for example, the push button Pb2 is ~0 2~

' pressed to work only the load 31a and the relay 32a or the relay 32b is actuated, if any one of the relay contacts becomes faulty and does not conduct, operation signals are applied to the ~udg-ing circuit 44 via the sensor 43 for detectlng operation signals but current is only induced at the sensor 41 by the two phases which are conducting. The judging circuit 44 detects this and judges that the relay is faulty on the basis of signals from both sensors 41,43 and opens the NFB 47 via the alarm circuit 46.
when two or three ~all) contacts have a bad connection, no elec-1~ tric current flows in the driving circuit 30 and only operationsignals are applied to the judging circuit 44, from which bad conduction o~ the relay can easily be found. At the termination of operation, if the load 31a continues to be driven due to fus-iny together of contacts, despite the release of the push button Pb2, signals are applied to the judging circuit 44 only from the sensor 41 for detecting driving current and no signals are applied from the sensor 43 for detecting operation signals, ~hereby faultines~ of the relay can be recognized.

If both the load 31a and the load 31b are working nor-mally with the push buttons Pb2 and Pb3 depressed and -the push button Pb~ is pressed to work the third load 31c but the relay 32e (or 32f) is faulty and one of the contacts is bad, electric current flows to the phase connecting to the remaining two contacts.
Therefore, electric current among the three alternating phases becomes out of balance and this unbalance can be recognized by the induced current in the sensor 41. If two or three contacts are bad, electrtc current in the operation circuit 33 increases due to closing of the push button Pb4, but the increase of elec-tric current is not recognized in the driving circuit 30. This indicates that the relay is faultyO

lo Embodiment 2 This embodiment is shown in ~ig. 5. A relay trouble detecting device 50 shown in this embodiment is so deslgned that a main electromagnetic contact 52 is opened by the operation of an alarm circuit 51. The alarm ~ircuit 51 is connected to the side of the normally closed terminal 45a of the switching contact 45 provided in the operation box 42 Isame as in the case of Embodiment 1) and carries a push button Pb5 and a solenoid coil MC7 of the main electromagnetic contact 52. Under this arrange-ment, on starting the push button Pb5 is first pressed to closethe main electromagnetic contact 52. If a bad contact occurs, the fault is detected in the same way as in Embodiment l and the switching contact 45 is switched over to release the main elec-tromagnetic contact 52. In Embodiments 1 and 2, an example o~
using three-phase AC is shown as a driving power source but it is applicable ko single phase AC. In the embodiments, AC ls adopted for the relay operation circuit 33 and a current transformer is used as the sensor for detecting operation signals, but in the case where DC is used for the operation circuit, electric current flowing in the operation circuit can be detected by a DC gal vanometer or other proper means.
Embodiment 3 This embodiment is shown in Fig. 6. In the preceding embodiments, driving current flowing in the driving circuit 30 _ g _ ~ ~64~

and operating current ~lowiny in operation circuit 33 are detected by the detecting sensors 41 and 43, respectively and de-tecting signals from the both sensors ~ 3 are input to the judging circuit ~. In this embodiment, however, a sensor for detecting operation current is omitted and with the operatlon of a relay, operation signals are input directly to the ~udging cir-cuit. A relay 60 provided in the driving circuit 30 connecting to the load 31 is a relay of semi-conductor element (hereinafter referred to as soLid-state relay, abbreviated as SSR), using a light shielding system as a switch 61.

In the above relay 60, due to the construction of the SSR, voltage is generated at its secondary side by the influence of leakage current, even if input signals are in the OFF state, and it is not appropriate to use a relay for detecting the sec-ondary side.

A relay trouble detecting device 62 in this embodiment comprises the sensor 41 for detecting driYing current ~same as the sensor 41 of the preced1ng embodiment provided for the driv-ing circuit 30 to the load 31), a relay operating circuit 63 r such as an interface circuit for the relay 60 (SSR) for switching the driving circuit, and a ~udging circuit 64. Operating signals of the switch 61 are input to the ~udging circuit 64 from the relay operating clrcuit 63. The switch 61 is of light shielding type and comprises a light emitting elem~nt LEC, a light receiv-ing element PD ana a light shielding plate 65 which is interposed between the two elements and is shifted to and from the light shielding position. Switch signals are transmitted to the relay operating circuit ~3 in a control box ~7 via a signal transmit-ting circuit 66. While the relay operating circuit ~3 gives op-erating signals to the relay (SSR) 60, the operating signals are input to the judging circult 64. In Fig. 6, LP and RSW are a lamp for information and a resetting switch, respectively for the judging circuit 64. Numeral 70 is a switch circuit for a contact 72 to be provlded in an alarm circuit 71. The alarm circuit 71 .

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operates the NFB ~7. under this arrangement, detecting signals from the sensor 41 for detecting driving curren~ and the switch closing signals from the switch 61 are compared at the judging circuit 64 to judge whether the relay 60 is good or bad. I~ a fault occurs, the alarm circult 71 is closed immediately and the driving circuit 30 is opened. In this embodlment, the relay 60 provided ;., ,.,., .;. ~

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~2 -in ~he driving clrcui-t 30 and the switch 61 are of non-contact -type bu~ the switch is not neces3arily required to be of non-contact type and a switeh de~ioe o-E con-tact -type may be used.
Embodiment 4 Thi~ embodirnent is shown in Fig. 7 and Fig. 80 In this embodiment~ a relay trouble detecting deviee is composed of a plurality o~ sensing members, one of which is called a main deviee ~nd the others are called supplemental deviees. While the main deviee alone has breal~ing function of NFB, the supplemental devices have terminals (for signal transmitting) to the main deviee. On the basis of relay trouble signals deteeted by the main device, by the supplemental ~e~iee or by both the main deviee and the supplemental deviee 9 trouble signals (for breaking the NFB at thé
main device) are issuedO A plurality oF loads, for example, three loads 31a, 31by 31e are eonneeted to the eo~mon driving eireuit 300` Also, the NFB 47is provided in the common driving cireuit 300 Relays for eireuit switehing 80a, 80b; 80e are provided in braneh driving circuit~ 30a, 30b, 30c respectively eonneeted to the load 31a, 31b~ 31e. MC shows a magnet coil and PB shows a push but~on.
A relay trouble detee-ting deviee 81 for relays 80a, 80b9 80e eomprises a plurality of sensing member3 82, 83~ 84, o~ whieh -the sending member 82 is ealled a main device and the sensing members 83, 84 are ealled supplemental de~ices. The main device 82 is equipped , ~ ~ 3 ~ ~

with a sensor 85 for detecting driving current provlded in the branch driving circuit 30a, a sensor 87 for detectlng operation current provide,d in an operation circuit 86a for the relay 80a, a judging clrcuit 88 to judge whether the relay 80a is good or bad by the input signals from both sensors 85,87 and a switching means 89 for an alarm circuit 90. The sensor 85 for detecting driving current is composed of a current transformer as in the case of the preceding embodiments. In this embodiment, a power source for driving the main device 82 is electric current obtained from the sensor 85 for detecting driving current and therefore the driving power source circuit for the main device 82 can be omittedO The sensor 87 for detecting operation current detects presence of operation current by utilizing a current transformer. An output terminal is connected to the judging cir-cuit 88.

The alarm circuit 90 is for opening the NFs and the switching means 89 mainly comprises a SSR, such as a triac, and makes the alarm circuit 90 go ON when an abnormality occurs.
Both the supplemental device 83 and the supplemental device 84 are of the same construction and are described below. Similarly to the main device a2, the supplemental devic~ 83 carries a sen-sor 91 for detecting driving current for the branch driving cir-cuit 30b, a sensor 92 for detecting operation current provided in the operation circuit 86b of the relay 80b and a judging clrcuit 93, but lacks the alarm circuit switching means 89 which is pro-vided for the main device.

Similarly to the main device 82, sensors 91 and 92 are provided with a current transformer and terminals 95 for trans~
mitting signals and are connected to the main device 82 by means o~ connecting cords 94. When an abnormality is detected in the relay ~Ob, the switching means 89 provided in the main device is operated. Simi].arly to the main device 82, the supplemental device 83 takes the output from the sensor 91 as its driving power source.

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For the other supplemental device 84, like symbol num bers are given to like parts and explanation of it is omitted.
However, 86c is the operation circuit for the relay 80c.

In the above composition, when the relays 80a,80b,80c are in nor~al condition, any one (for example, 86a) of the relay operating circuits 86a,86b,86c is ON and when driving current is applied to the load 31a, both the sensor 85 for detecting driving current and the sensor 87 for detecting operation current give signal current, which the ~udging circuit 88 detects. The switching means 89 and thus the SSR, are not operated. This applies where all relay operation circuits 86a,86b,86c are OFF
and the branch driving circuits 30a,30b,30c are OFF. However, even if any one (80b, for example) of the relays 80a,80b,80c has become faulty and the relay .

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operating circui-t 86b is in the OFE' state, so long as electric current flows in three phases or two phases of the branch driving circuit 30b, the supplemental device 83 detects it at the ~udglng circult 93 and switches the alarm circuit switching means at the main device 82 ON, thereby putting the alarm circuit into the conducting state and opening the NFB 47.

Fig. 8 is a plan view of the main device 82. In Fig.
8, terminals 96a,96b are connecting terminals for the operation circuit 86a; 96c,96d are connecting terminals for the switching means 89; and 96e,96f,96g are connecting terminals for the sup-plemental devices 83 and 84.

Embodiment 5 This embodiment is shown in Fig. 5. Thick wires are used for the driving circuit 30 common to loads 31a,31b,31c to carry heavy current.

A relay trouble detecting d~.vice 100 comprises two sensing members 101,102 ~hereinafter the sensing member 101 is referred to as a main device and the sensing member 102 is re:Eerred to as a supplemental devlce). The main device 101 ls provided with a current transformer 104 for an arbltrary one phase (R-phase, for example) in the driving circuit 30, a switch-ing means 108 for a judging circuit 30 and an alarm circuit 109 r and a sensor 111 for detecting operation current provided in a relay operation circuit 110. The alarm circuit 109 comprises an operation circuit ~or an NFB 107. The switching means 108 is mainly composed of SSR as in the preceding embodiments. The sup-plemental device 102 1s provided with a current transformer 105 for the other one phase (T-phase r for example) in the driving circuit 30, a judging circuit 113 to ~udge whether the relay is good or bad by input signals of a sensor 112 ~or detec-ting opera-tion current provided in a relay operation circuit 110 and termi-nals 115 for transmitting signals connected to the main device 3~

101 by cormecting cords 114. ~elays 120a,120b .... 120f for nor-mal and reverse driving of each load 31a,31b,31c are arranged in parallel in the relay operation circuit 110 and when any one of the relays becomes ON, operation current is detected by the sen-sors 111 and 112 for detecting operation current.

A current transformer is applied to the sensors 111,112 for detecting operation current as in the case of the preceding smbodiment. In Fig. 9, PBl,PB2 ..~. PB4 are push button switches of the interlock type. In thls embodiment, a driving power source for the relay trouble detecting device 100 is electric current obtalned from the sensor 103 for detecting driving cur-rent.

In the above embodiment, in the case where relays 20arl20b ...~ 120f are in normal condition, if any one of the relays ~the relay 120a, for example) is ON and driving current is applied to the corresponding load 31a, the sensor 103 for detect-ing driving current and the sensors 111,112 for detecting ... .

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operation current generate signal current, whlch is applied to the judging circuits 106,113. In the case where all the relays 120a,120b .... 120f are OFF, no electric current flows in the driving circuit 30. In either case, judging circuits 106,113 do not make the alarm circuit 109 ~namel~, SSR) ON.

Even when any one of the relays 120a,120b .... 120f has become faulty and the relay operation circuit 110 is OFF, so long as electric current flows to three phases or two phases of the 10driving circuit 30, the sensor 103 for detecting driving current operates and applies signal current to the ~udging circuits 106 and 113 or any one of 116 and 113. Thus, the ~udging circuit 106,113 make the switching means 109 ON and open the NFB 107.

15In the described embodiments, when a relay provided in a driving circuit for load has gone wrong, the contact of one or rnore relays is bad and current does not flow upon operation of the relay or when the relay contacts do not break upon release of the relay, such trouble is detected from electric current flowing in the driving circuit and the relay circuit. An alarm is given and unforseen accidents can be prevented.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A relay malfunction detecting device, comprising: a sensor for detecting driving current provided in a driving circuit which connects a power source with a load, and a judging circuit to which detecting signals from said sensor and operations signals of a relay operation circuit are applied, said sensor being operable to apply detecting signals corresponding to applied load current to said judging circuit, which judging circuit is operable to examine the mutual variation relation between the detecting signal and the operation signal and operate an alarm circuit selectively.

2. A detecting device as claimed in claim 1, wherein the sensor for detecting driving current is a current transformer.

3. A detecting device as claimed in claim 1, wherein the driving circuit is single phase or three- phase AC and the sensor for detecting driving current comprises a current transformer.

4. A detecting device as claimed in claim 1, wherein the sensor for detecting driving current is a current transformer and output signals of said current transformer provide power for operation of the device.

5. A detecting device as claimed in claim 1, wherein the driving circuit is three-phase AC and the sensor for detecting driving current is a current transformer common to each phase and equipped with a judging circuit to judge the applied current of each phase.

6. A detecting device as claimed in claim 1, wherein the driving circuit is single-phase or three-phase AC, the sensor for detecting driving current comprises a plurality of current transformers for detecting each phase, each provided for conductors of at least two phases, and a main current transformer, a secondary output of the transformer for detecting each phase being connected to the main current transformer.

7. A detecting device as claimed in claim 1, wherein said means for generating relay operation of signals comprises a sensor for detecting operation signals.

8. A detecting device as claimed in claim 7, wherein the sensor for detecting operation signals is a current transformer.

9. A detecting device as claimed in claim 1, wherein an alarm circuit is connected to a no-fuse breaker (NFB) operating circuit provided in the driving circuit.

10. A detecting device as claimed in claim 1, wherein the alarm circuit forms an operating circuit for an electromagnetic contact for switching the driving circuit and is closed normally but is opened by a signal from the judging circuit.

11. A detecting device as claimed in claim 17 wherein a switching means for the alarm circuit is a solid-state relay.

12. A detecting device as claimed in claim 1, wherein a switching means for the alarm circuit is a contact relay.

13. A detecting device as claimed in claim 1, further comprising a plurality of sensing members, one of which is a main device and the others are supplemental devices, said main device being provided with the sensor for detecting driving current, the judging circuit and a circuit for operating the alarm circuit and the supplemental circuit being provided with the sensor for detecting driving current, the judging circuit and output terminals to transmit output signals of the judging circuit to the main device.

14. A detecting device as claimed in claim 13, wherein a plurality of loads are connected in parallel to the driving circuit, the main device is arranged in a branch driving circuit for one load and the supplemental devices are arranged in each branch driving circuit for the other loads.