FR2504748A1 - SEMICONDUCTOR LOAD PROTECTION DEVICE WITH ELECTRONIC SIMULATION OF THE HEATING OF AN ENGINE - Google Patents

Abstract

THE DEVICE ACCORDING TO THE INVENTION INCLUDES A SENSOR 14 WHICH DETECTS THE CURRENT IN AN ELECTRIC CIRCUIT, AN OVERLOAD DEVICE 26 IN REVERSE TIME CONNECTED TO THE SENSOR AND DETECTING THE THERMAL STATE OF THE LOAD, TO PRODUCE A SIGNAL TO A TRIP DEVICE 38 CONTROL CIRCUIT, THE LATTER COMMANDING THE ELECTRICAL CIRCUIT WHEN THIS SIGNAL IS GENERATED.

Description

SEMICONDUCTOR LOAD PROTECTION DEVICE

  WITH ELECTRONIC HEATING SIMULATION

OF AN ENGINE

  The present invention relates to a

  in general to tank protection devices

  semiconductor, and concerns more particularly-

  an electronic simulation of the heating characteristics of an engine allowing a load protection device to precisely control

  the thermal state of an engine or load.

  It is known that certain load protection devices perform various functions

  protection, for example the detection of overcurrent

  tee, phase break and earth faults.

  These functions generally introduce a time of

  tripping for a circuit breaker and associated load

  ciée, this tripping time being an independent function

  pours the square of the intensity of the current flowing in the load to be protected In other words, an inverse time relationship is generally applied, the instant

  at which a fault is detected and the instant of the dis-

  junction being in inverse relation so that it re-

  following a strong overcurrent a short period for triggering the device while a fault of

  relatively reduced overcurrent leads to a peri

  relatively long before triggering Types of devices that operate in this manner are described in United States Patents

  NO 4,021,703, NO 3,996,499, 3,818,275 and NO 3,602,783.

  However, the aforementioned patents impose numerous components.

  to simulate the thermal state of a load, ne-

  stopping separate components for triggering

  as well as for resting the use of

  separate trigger and quiescent poses

  in the prior art to simulate the ther-

  load behavior produces uncertainty as to whether the load has heated up beyond or

  has cooled below nominal values.

  In its broadest form, the invention therefore relates to a charge protection device intended to protect an electrical circuit against

  overcurrents, and which includes a device for

  detection of the current flowing in an electric circuit

  this detection device producing a sig-

  output nal which is a function of the current flowing; a connected reverse time overload device

  to the detection device to detect the thermal state

  load, and producing a signal for a circuit control trip device, the latter signal being produced at an instant which is

  depending on the thermal state of the load; a provision

  capacitive device connected to the sur-

  reverse time charging comprising a device for raising the voltage level in the capacitor device as a function of the thermal state of the load; and a circuit control trip device connected to the reverse time overload device and the electrical circuit for controlling

  the latter when the last signal is produced.

  In an embodiment which will be de-

  crit below, a load protection device

  includes an electronic simulation of the heater

  of a motor A current sensor is used to produce an output signal which is function

  of current flowing in an electrical circuit.

  A reverse time overload device is con-

  connected to the sensor and includes a storage device

  sinage to detect the thermal state of the load,

  producing a signal for a trip device

  circuit control ment at a time which is

  depending on the thermal state of the load A device

  tif storage is connected to the overload device in reverse time so that the level

  electrical potential in the storage device

  sinage is a function of the thermal state of the load.

  A circuit control device is connected to the reverse time overload device and the electrical circuit to control the latter when the signal is produced by the device.

reverse time overload.

  Other features and benefits of

  the invention will appear during the description

  which will follow from an exemplary embodiment and with reference to the appended drawings in which: FIG. 1 is a diagram of a load protection device with semiconductors, according to an embodiment of the invention, comprising

  part of the electrical device or circuit ex-

  Figure 1 A is a diagram of a device for detecting earth faults,

  Figure 2 is a tri-

  phase of a contactor comprising the semiconductor load protection device,

  Figure 2 A is a mono- representation

  phase of a contactor comprising the semiconductor load protection device, FIG. 3 is a block diagram of a semiconductor load protection device showing the signal circuits for different fault conditions,

  Figure 4 is a graphical representation

  only the percentage of overcurrent as a function of the time necessary to cause the electrical device or circuit to trip, and

  Figure 5 is a representation of in-

  physical connection of the device of Figures 1, 1 A, 2 and 2 A.

  Throughout the description,

  similar posers will be identified by the same

  numerical references Modified components, similar

  areas in basic operation, to those already described,

  but different in their use, will be identi-

  trusted by references already assigned with the addition

a premium (').

  The Figures, and more particularly Figure 2, represent a circuit protection device 12 The circuit protection device 12 comprises, in this embodiment of the invention, a three-phase line comprising conductors or lines Li, L 2 and L 3 which are connected on the right to a three-phase load and on the left to a three-phase source of electric current Between the load and the electric current source is a current sensor 14 and, connected in series, a circuit breaker

  or motor contactor 16 In the embodiment

  tion of Figure 2, a single current IL is shown, flowing in the line LI It is understood that

  other currents can circulate, and circulate generally

  generally in the other lines L 2 and L 3 and these other currents can be a function of the current IL The choice of the current IL is simply made for the purpose

to simplify the representation.

  The current sensor 14 has two output terminals which are designated by 18 and 20 A load resistance module 22 is shown, connected to terminals 18 and 20 The load resistance module 22 consists of a resistive element which can be connected to the terminals 18 and 20 to convert the current IL into a voltage V which can be used by another device

  circuit protection in the device of Fig 2.

  The load resistance module 22 can be connected

  tee in parallel with a fault module 24 at the

  earth, a reverse time logic circuit 26, a circuit

  phase break detection 28 and an accessory module 30 which may include elements such as a control panel, an overload state indicator or long acceleration modules which are described in more detail in the United States Patent from America NO 3 996 499 cited above The other elements can be connected for example to terminals 32 and 34 It is understood that modules 24 and 30 can be omitted

  or replaced and that other modules can be added

  tees provided that the parallel connection relationship

  with the load resistance module 22 is maintained.

  Each of the circuits 24, 26, 28 and 30 already mentioned for example has an output terminal which can be connected to a line 36 which, in turn, is connected to an output switch 38 which controls the line 40

  which, in turn, is connected to the circuit breaker or contact

  tor of motor 16 already mentioned In this embodiment of the invention, the voltage V across the terminals

  output 18 and 20 is proportional to the current IL.

  If the anticipated increase in the IL current becomes sufficient

  large enough, a different load resistance can

  be placed between terminals 18 and 20 so that the voltage

  Zion between these terminals is approximately the same, even if the current IL is much more intense La

  same compensation by substitution of a resistor ap-

  property may apply if the nominal current range

  nal is significantly lower This means that elements 24 to 30 do not have to be changed because they do not

  are sensitive only to the voltage V This means also

  there is no need to change the output switch 38 Consequently, the value of the load resistor 22 is modified so that the voltage V enters

  terminals 18 and 20 is roughly the same, independent

  particularly the current characteristics of the load when the latter operates at nominal current

  100 percent logic circuit 26 of reverse time

  fulfills the function I T well known in this tech-

  In summary, the reverse time logic circuit 26 delivers an output signal at a period which varies with the value of the voltage V appearing at its input. Figure 2A shows another protection device 12 'intended to be used in the case of a

  load and from a single-phase or direct current source.

  This embodiment of the invention comprises a single

  single phase or continuous line Ll which supplies the

  tion to a single-phase or continuous load on the right, from a single-phase or continuous source on the

  left It also has a circuit breaker or contact

  16 'single contact motor tor, including a con-

  tact S to interrupt the current IL 'In the case of

  alternating current, the current sensor

  14 'can be the same as that of Figure 2 The mo-

  dule 24 'of load resistance differs from module 22 of load resistance of Fig 2 in that the total current IL' can be significantly different from the range of

  current IL of Fig 2 and therefore, with likely-

  a higher resistance value so that the voltage V is roughly in the same values as

  those of the device of Figure 2 But the lo-

  gic 26 'of reverse time and the accessory module 20' can be similar to the corresponding modules of Fig 2 This brings out the flexibility of use of the circuit protection device It should be noted that there is no detection of breakage phase in this embodiment, because this function is typical of a device with alternating polyphase electric current. It should also be noted that the outputs of the modules 26 ′ and par for example are connected to line 36 ’which, in turn, is connected to the input of the output switch 38 'which itself controls the line 40' in order to actuate the circuit breaker or motor starter 16 'In a similar way to that of Fig 2, the output switch controls the line 4 o in order to activate the circuit breaker or the

motor contactor 16.

  Figure 5 is a physical interconnection drawing for the device shown in Figures 1, 1 A and 2 It represents the housing 58 of the protection device which encloses the electronic circuits shown in Figure 1, except for the circuit breaker -

  or the motor contactor 16, the charger

  ge M and the load resistance module 22 The power supply

  the circuit is applied to terminals A and B at the top of the housing 58, next to which are

  the sleep button and the trip indicator

  LED 2 The contacts for the RE 1 relay are also

  at the top of the housing 58 Line conductors

  Ll, L 2 and L 3 go through current transformers

  site which are in the housing 58, allowing the load protection device to be interposed in series in the electrical circuit Modules 60, such as that shown in FIG. 5, comprising module pins 62 are produced so as to match the device connection terminals 66

  protection The connection terminals 66 of the device

  protective tif are arranged to allow

  the introduction of module 60, in only one possible way.

  These connection terminals 66 of the protection device

  are used by modules 60 to fulfill functions

  tions on the circuit protection device At the rear of the modules 60 there are pins 64 for module crossing which allow other modules

  similar 60 are "twinned" thus allowing

  read several modules 60 The connection terminals 66 of the protection device are arranged in a redundant manner, with the exception of the ground fault terminal GF, thus allowing the modules 60 to be inserted in the left or right of

  protection device connection terminals 66.

  j 5 The boot 58 of the protective device can be

  mounted using mounting brackets 68, on any

  which surface is suitable, thus being able to be

  worm in close proximity to the equipment to be protected.

  Regarding the implementation of the device

  protection, Figure 1 shows an embodiment

  sation of the invention intended for a three-phase line, with a three-phase source, for controlling a motor M which consists of a three-phase load In this embodiment of the invention, the electrical and electronic elements constituting the current sensor 14, the load resistance module 22, the logic circuit

  of reverse time, the output 52, the apparatus 16 of con-

  motor tactor, the logic circuit 28 for phase failure, the power source 54 and the test circuit 56 are shown in Schematic form.

  case, a current IL which circulates in the line L1 is de-

  tected by a CT 1 current transformer in the cap-

  current tester 14 Resistor R 2 in series with the

  potentiometer Pl represented in module 22 of resistance

  load tance constitutes this module 22 already described, at the terminals of which the output voltage V appears. It should be noted that the potentiometer Pl may be a resistor

  fixed if a specific load calibration is known.

  Similarly, in lines L 2 and L 3 the

  current IL flows through the current sensor 14,

  from CT 2 and CT 3 current transformers

  combining a voltage across the terminals of the load resistance module 22 The current induced in the current transformers CT 1, CT 2 and CT 3 is rectified in a three-phase pon t circuit constituted by diodes Dl, D 2, D 3, D 4, D 5 and D 6 A varistor Vi is connected to the output

of the three-phase bridge circuit.

  The neutral branches of the current transformer

  CT 1, CT 2, CT 3 are connected to one end of a re-

  resistance Ri and to a GF terminal of earth fault.

  The other end of the resistor RI is connected between the resistor R 2 and the potentiometer Pi The output of the current sensor 14 essentially produces a unidirectional voltage such as the connection to the resistor

  R 2 is called a positive terminal 42 while the con-

  connection to potentiometer P1 is called a negative terminal 44, corresponding respectively to the output terminals 18 and 20 of the current sensor 14 It should be noted

  that the negative terminal 44 and the earth of the circuit (called

  earth) are at the same potential The terminal posi-

  tive 42 is connected to the cathode of diode D 7, to one end of resistors R 4, R 9 and R 14 and to the anodes of diodes D 9 and D 10 The negative terminal 44 is connected to an armature of capacitors C 1, C 5 and C 6

  as well as the anode of a Zener ZD 6 diode, an arma-

  of the capacitor C 8, at the negative supply inputs of the operational amplifier OA 1, and at the

  comparator MC 7, as well as at one end of the resistors

  these R 32 and R 36 and finally, to the emitters of the transistors T 1 and T 2 The anode of the diode D 7 is connected to the other

  armature of capacitor C 1 as well as at the other end

  of resistor R 4 The anode of diode D 7 is also connected to the cathode of Zener diode ZD 1, to one end of resistor R 12 and to the negative input signal terminal of comparator RC 4 L the other end of the resistor R 9 is connected to the cursor and to a terminal of the potentiometer P 2, to an armature of the capacitor C 2, to the anode of the Zener diode ZD 1, to the terminal of positive input signals- comparators MC 4 and MC 3 as well as the anode of the diode D 8 The cathode D 8 is connected to the negative input signal terminal of the comparator MC 4, at the other end of the resistor R 12 and at one end of resistors R 25 and R 27, at

  the anode of diode D 14 and the cathode of diode D 13.

  The other armature of the capacitor C 2 is connected to

  the other terminal of potentiometer P 2 and to electrical ground

  that the cathode of diode D 9 is connected to an ex-

  end of resistor R 17 The cathode of diode D 10 O is connected to the cathode of diode Zener ZD 3

  and at one end of the resistor R 24 The other end

  of resistor R 17 is connected to one end of resistor R 15, to one end of resistor R 21 and to the comparator output signal terminal

  MC 4 The other end of resistor R 14 is connected

  t 50474 I tee at the other end of resistors R 15 and R 25,

  at one end of the resistor R 16 and of the condensa

  C 9, at the positive supply inputs of the am-

  operational amplifier OA 1 and comparator MC 7, at one end of a break contact SW 1, at one end

  resistor R 30 and in auto mode contact

  switch 51, and finally to the cathodes of the Zener ZD 9 and ZD 10 diodes which are part of the circuit

  supply bridge 46 The other end of the

  resistor R 16 is connected to the output signal terminal of comparator MC 3, to the anode of diode Dll and to one end of resistor R 20 The cathode of diode Dll and the other end of resistor R 20 are connected to the cathode of the diode D 12 and to the cathode of the Zener diode ZD 4 The anode of the diode D 12 is connected at one end of the resistor R 22 to the other end of the resistor R 22, at the negative input terminal of the operational amplifier OA 1 and the other armature of the capacitor C 6 The anode of the diode D 13 is connected to the other end of the resistor R 21 and of the capacitor C 5 as well as to the negative input signal terminal of the MC 8 comparator The negative input signal terminal of the MC 8 comparator

  is connected to the trip terminal (T) The

  thode of diode D 14 is connected to the cathode of Zener diode ZD 6 and to the negative input signal terminal of comparator MC 7 The anode of Zener diode ZD 3 is connected to the other end of the resistor R 22. A guard band surrounds the connections o

  resistors R 22 and R 24 meet, the conden-

  sator C 6, the negative input signal terminal of the operational amplifier OA 1 and the anode of the diode D 12 The guard strip is of an electrically conductive strip surrounding the aforementioned connections on both sides a printed circuit board which is the preferred embodiment, this guard strip being

  electrically connected to the cathode of diode D 13.

  The function of the guard band is to surround the

  critical signal circuits that can be affected

  ted by card impedances that can affect

  circuit operation These impedances are pro-

  picked up by things like map construction, cleanliness, and humidity Using a

  guard strip minimizes the possibility of

  card pedances between ground or supply voltages

  ment, causing false signals in the circuits.

  Figure 1A shows the circuit 24 of deran-

  ground connections intended to be interconnected with the circuits of Figure 1 Interconnections are made

  by terminals GF, -, +, T and K of circuit 24 of deran-

  earthed connections with terminals GF, -, +, T and K

of the diagram in Fig 1.

  Terminal GF of earth faults circuit 24 is connected to one end of the resistor

  R 8 the other end of which is connected to the input terminals

  input of positive and negative signals from comparators MC 1 and MC 2 respectively The negative (-) terminal is

  connected to one end of the -resistance R 5, to the ano-

  from the Zener ZD 2 diode, to a capacitive armature

  C 4 and C 7, at the negative supply input of the comparator MC 6, at one end of the resistor R 26 and at the cathode of a silicon-controlled rectifier

  SC 1 The positive (+) terminal is connected to an

  resistor R 7 and R 19 The trip terminal

  (T) is connected to the cathode of diode D 15.

  The other end of resistor R 5 is con-

  connected to the negative signal input terminal of the

  parator MC 1 and to one terminal of the resistor R 6 The other end of the resistor R 6 is connected to a terminal of the potentiometer P 3 the other terminal of which is connected to

  its cursor, upon entering positive signals from the comparison

  MC 2 and to the other terminal of resistor R 7 The terminal

  ne of comparator MC 1 output signals is connected to the comparator MC 2 output signal terminal and

  at one end of the resistors R 10 and RI 1 The other ex-

  end of the resistor R 10 is connected to the negative signal input terminal of the comparator MC 5 and to a frame of the capacitor C 3, the other frame of which is grounded The other terminal of the resistor Rll is connected to a end of resistor R 13, at the

  positive power input terminal of MC 6, at ex-

  end of resistor R 23 at the anode of the diode

  LED 1, then to terminal K The other former

  end of the resistor R 13 is connected to the positive signal input terminal of the comparator MC 5, to the negative signal input terminal of the comparator MC 6 and to the cathode of the Zener diode ZD 2 The other terminal

  of resistor R 19 is connected to the signal terminal

  output of comparator MC 5 and at one end of resistor R 18 The other terminal of R 18 is connected to the positive signal input terminal of comparator MC 6 and to the other armature of C 4 The terminal of comparator output sigrux MC 6 is connected to the anode of

  the diode D 15 and to the cathode of the Zener diode ZD 5 thus

  if at the other terminal of R 23 The anode of the Zener diode ZD 5 is connected to the other terminal of C 7, R 26, then to the grid of the silicon-controlled rectifier SC 1 The positive terminal of SC 1 is connected to one end of resistor R 28, the other end of which is connected

  at the cathode of the LED 1.

  Returning to Figure 1, the other terminal of capacitor C 8 is connected to the positive signal input of operational amplifier OA 1, to the other

  resistor terminal R 27 and to one resistor terminal

  tance R 29 The output terminal of the operating amplifier

  tional OA 1 is connected to the positive signal input of comparator MC 7 The output terminal of comparator MC 7 is connected to the other terminal of resistor R 29 and to the cathode of diode D 16 The signal input positive of comparator MC 8 is connected to the anodes

  diodes D 16 and D 17 and from there to a terminal of the resis-

  tance R 31 The other terminal of resistor R 31 is con-

  connected to the central contact of the switch SI 1 The output signal terminal of the comparator MC 8 is connected to the cathode of the diode 17 and to the cathode of the Zener diode ZD 7 The anode of the Zener diode ZD 7 is connected to the other terminal of R 32 and at the base of an NPN transistor T 2 The other terminal of the resistor R 36 is connected to

  the base of an NPN transistor T 1, at an armature of the con-

  densifier Cll and at the anode of the Zener diode Z Dll Le

* collector of the transistor T 1 is connected to the other arma-

  ture of capacitor Cll, to the anode of the Zener diode ZD 8 and to the cathode of the light-emitting diode LED 2 The anode of the light-emitting diode LED 2 and the cathode of the Zener diode ZD 8 are connected to each other terminal of the resistor R 30 and to the "manual" contact switch 51 The cathode of the Zener diode Z Dll is connected to the anode of the diode D 20 and to one terminal of the resistor R 35 The other terminal of resistor R 35 is connected to terminal K The cathode

  of diode D 20 is connected to the collector of the transistor

  tor T 2, at the anode of the diode D 21 and at one terminal of the resistor R 3 The other terminal of the resistor R 3 is connected to one of the winding terminals of the relay

  RE 1 The other winding terminal of relay RE 1 is con-

  connected to the cathode of the diode D 21, to the other contact of a return switch SW 1 and from there to the terminal K. The other armature of the capacitor C 9 is connected to ground and also to the terminal circuit 46 negative

  One of the input terminals al-

  of circuit 46 in the supply bridge is con-

  connected to one terminal of resistor R 34, the other of which

  terminal is connected to terminal B The other input terminal

  very alternative of the circuit 46 in supply bridge is connected to one terminal of the resistor R 33 and of the capacitor C 10, the other terminals of the capacitor C 10 and of the resistor R 33 being connected together and to the terminal A. RE 1 relay contacts, (see Figure 1) are a set of single-pole working contacts, one terminal of which is connected to one winding terminal of the motor contactor device 16, the other winding terminal being connected to one terminal of a voltage source Vs The other terminal of the voltage source VS is connected to the other terminal of the contacts of the relay RE 1 The contacts which are in the motor contactor device 16, designated by 16 A, 16 Bet 16 C are working contacts and are connected in series with the conductors LI, L 2 and L 3 respectively Il

  it is understood that the motor contactor device 16

  can use a standard engine starter with start and stop buttons

to control the charge.

  Dass the preferred embodiment of the

  vention, the comparators MC 3, MC 4, M 7 and MC 8 make

  part of an integrated circuit box and therefore

  quent, although each of the four comparators needs

  care of an input signal, only a power source

  tion is required (see Table I).

  Due to the modularity of the invention,

  different connection points are provided to allow

  be to use different modules therefore for

  facilitate the possible replacement of module 22

  load resistance, a positive terminal 42 and a terminal

  negative 44 are provided, as already described, and equi-

  apply to terminals 18 and 20 in Fig 2 In addition, a

  trigger terminal designated by "T" allows injection

  ter a trigger signal so that the device

  protection disconnects the load from the Egale- source

  a GF ground fault terminal is provided to which the neutral branches of the current transformer CT 1, CT 2, CT 3 are connected. Similarly, a power supply terminal K supplies power to all

  circuits that may be required in a module.

  As far as now works

  Figure 3 illustrates the essential functions of the invention subdivided into construction elements These elements are based on circuits at the level of the components and illustrate

  the main signal circulation circuits.

  In summary, a power source 54 is used to power most of the elements of the device according to the invention. The power source uses a control or input voltage F 5 which

  can be for example 115 and 230 Volts at 50 or 60 Hz.

  The voltage is reduced or lowered to a usable voltage F 6 and rectified into a direct voltage F 7 which

  is then delivered to the different elements of the functions

  test 56, overcurrent and timing

  , phase break 28 and fault detection-

  grounded 24 In addition, reference voltages F 9 are produced from the DC power source, as well as a quiescent circuit intended

to the output function.

  A current detection function 14 is used to detect the intensity of the current drawn by the load. The current detection circuit FI delivers an alternating output which is then rectified into a DC voltage F 2, and converted into a voltage signal F 3 by a current source Consequently, the voltage produced by the current detection function 14 is proportional to the intensity of the current drawn by the tank. The voltage is used by the overcurrent and timing function 50, the function 24 of earth fault detection and

  the phase break function 28, because the current

  read by the load gives an indication of overcurrent,

  phase failure and faults to ground fa-

eyelashes to use.

  The logic circuit 50 of overcurrent and

  timer performs many functions The inten-

  sity of the current used by the load is detected in the form F 10, and therefore produces an indication of

  overcurrent The output of the fault detection circuit

  rant varies with the intensity of the current drawn by the load, so that in the case of a condition of

  overcurrent, it triggers a time switch F 12

2 SO 4145 -

  overcurrent porization If the current intensity in the load exceeds a predetermined value for

  a predetermined period, a trip switch

  F 14 is energized In addition, if the load produces a strong current demand, the overcurrent delay F 13 starts automatically In a similar way, under conditions F 1 l of hot start, when

  the load is hot, either by its operation

  continuous, either by a previous overheating, the intensity of the starting load current is controlled, so that the overcurrent delay F 13 can cause the tripping switch F 14 to trip if, as already indicated, the current in the load exceeds a predetermined intensity, but for

  a shorter predetermined period.

  The test circuit on site 56 allows the direct supply current F 7 to supply the switch F 12

  of overcurrent delay of the overcurrent circuit

  time delay 50, thus triggering the commu-

  trip trigger P 14 by simulating a fault condition allowing the control 8 F 4 of the

  semiconductor protection according to the invention.

  The earth fault detection circuit 24 uses the voltage F 3 produced by the circuit

  14 current detection to determine whether a condition

  earth fault F 19 exists, causing

  thus the initialization of the delay F 20 of deran-

  Grounding After the detection of a ground fault exceeding a predetermined level for a predetermined period, the module is triggered, thus energizing an indicator F 22

of earth disturbance.

  The phase-break circuit 28 controls the

  voltage produced by the circuit 14 for detecting the

  rant Upon detection of a phase break fault F 15, a switch F 16 for phase break delay

  is triggered, so that the additional switch

  re-release F 18 operates after a pre-

determined F 17.

  The output circuit 52 controls the state of the

  basic trigger switch P 14 forming part of

  tie of the overcurrent and tempo logic circuit 50

  as well as the output of the additional trip switch F 18 forming part of the circuit 28

  phase failure On detection of a signal

  tripping, the relay control transistor F 25 de-energizes a control relay F 26 which, in turn, controls a contactor P 25 which disconnects the power supply from the load In addition, the circuit F 25

  of relay control transistor causes production

  tion of an indication F 24, as well as a "locking" F 23 in the output condition, so that the control relay keeps the contact open until a

  signal F 8 to quiesce is received.

  A detailed description of the circuits will be

  now done Regarding the power source

  54, Figure 1 shows that this circuit 54 is des-

  tined to operate continuously from a voltage source which is connected to the supply terminals "A" and "B" and which can be, as indicated, / 130 Volts, at 50/60 Hz depending on the value of the components chosen The lowering of the voltage

  input is made using a conden-

  sator C 10 as a voltage drop component The resistor R 33 is dimensioned so as to present a discharge circuit to the capacitor CIO while the resistor R 34 is used as a current limiter The power bridge circuit 46 using the diodes D 18, D 19, ZD 9 and ZD 1 O converts the voltage

  input input of terminals "A" and "B" in a voltage

  The two diodes 7 ener ZD 9 and ZD 10 limit

  try the maximum continuous voltage The ripple alternates

  native is reduced by a filter capacitor C 9; The supply voltage VK directly supplies the system comparators MC 1, MC 2, MC 3, MC 4, Mc 5, Mc 6, t SO-4748 MC 7 and MC 8 as well as the operational amplifier OA-1 note that the comparators MC 1 and MC 8

  are part of integrated circuits (IC) which, like the

  as shown in Table I, have four comparators per integrated circuit.

  In the present embodiment, the com-

  meters MC 1 to MC 8 are polarized so that if the voltage at the positive input signal terminal is greater than the voltage at the input signal terminal

  negative, the output terminal has a high impe

  dance, and is therefore essentially

  connected from the rest of the circuit while if the voltage at the negative input signal terminal is greater than the voltage at the positive signal input terminal, the comparator output is electronically connected to the negative power input of the associated integrated circuit, therefore being grounded as shown in the diagrams in Figures 1 and 1 A.

Table I

  Integrated Circuit IC-2 IC -2 IC-1 IC-1

IC-2

  IC -2 IC-1 IC-1 Designation MC 1 MC 2 MC 3 MC 4 MC 5 MC 6 MC 7 MC 8 Function Earth fault detection comparator Earth fault detection comparator Switch comparator

over-time delay

  current switch comparator

rup timer

phase ture

Timing comparator

earth faults

Timing comparator

earth faults

Trigger comparator

  overcurrent Switch comparator

additional trigger

OA-1 IC 3 buffer

2504? 41

  In addition, the supply voltage VK lights up

  trigger indicators, LEDs

  luminescent LED 1, LED 2, the output circuit 52, the

  test circuit 56 and the reference voltage branch

  Reference voltages V 1, V 2 are produced from the supply voltage VK, using

  resistor R 25, diode D 14 and the lead diode ZD 6.

  Therefore, two reference voltages are pro-

  picks, the first reference voltage V 1 appears

  health at the anode of diode D 14 to determine the tempo-

  overcurrent and the set points of

  switching of comparators MC 3 and MC 4 (see table I).

  The second reference voltage V 2 produced at the

  Zener diode ZD 6 diode provides the reference signal

  Reference to the MC 7 comparator for tripping by overcurrent

  between the operational amplifier OA-1 and the output circuits 52 Two reference voltages are

  necessary to ensure operation at voltages

  reduced input sions * which may appear at the

nes "A" and "B".

  Regarding the current sensor i 4, the three lines L 1, L 2 and L 3 of a three-phase source

  are connected in series respectively with the con-

  16 A, 16 B and 16 C working tacts of the circuit breaker or

  the motor contactor apparatus 16, at a tri-

  phased, for example an M motor Transformers

  of intensity CT 1, CT 2 and CT 3 which are in the box

  protective tier 58 of Fig 5 are arranged respectively

  tively on lines L 1, L 2 and L 3 to sample the current drawn by the load M The current transformers CT 1, CT 2 and CT 3 can be connected in

  star, producing an alternating current proportion-

  nel to the primary current IL drawn by the load M The alternating current is then rectified into a direct current using the diodes D 1, D 2, D 3, D 4, D 5 and

  D 6 constituting a three-phase bridge A varistor V 1 as-

  on transient overvoltage protection

  which can be produced by inputs from trans-

  250 474 e intensity trainers CT 1, CT 2 and CT 3 The output of the diodes DI to D 6 is converted into a direct voltage proportional to the current IL drawn by the load,

  by means of the load resistor 22 For an inten-

  sity given, the amplitude of this voltage at 100 percent of the load M is constant and determined by the value of the load resistance 22, so that the values of the resistance R 2 and of the potentiometer Pl are adjusted so to produce the same voltage as at terminals "+" 42 and "-" 44 regardless of the value

  load M Therefore, the value of the resistance

  load tance 22 is chosen essentially for

  "correspond" to the different charges M, having all

  days the same voltage across the terminals It is understood that the load resistor 22 can be permanently introduced into the associated load protection circuit, but in the present embodiment, it

  constitutes a module 22 as shown in Figure 2.

  The continuous output of the three-phase bridge rectifiers DI to D 6 is proportional to the maximum difference between two of the three three-phase currents Therefore, when the motor phase currents are equal, the minimum continuous voltage of the resulting waveform can be for example about 0.866 times the maximum continuous voltage, and the ripple frequency is six times the line frequency When the load or motor

  M undergoes a phase break, the DC voltage pro-

  pick is a continuous output signal that looks like

  the output of a single-phase bridge rectifier Therefore

  quent, in the present embodiment of the invention

  tion, the load resistance module 22 must have a resistance of for example 60 to 600 Ohms so as to deliver an output voltage at the positive and negative terminals 42 and 44, for example on average of 10 V

  for a current IL in a load M at 100% o.

  The overcurrent circuit (see also Fig 3) produces an overcurrent trip of a contactor, based on the current-time relationship

2504? 48

  (I 2 T) basically derived from the heating in

  a load M Consequently, for currents IL de-

  passing 115 percent of the current at full load M,

  being able to produce for example 11.5 Volts at the terminal po-

  sitive 42, the overcurrent circuit 50 triggers a timing sequence The timing speed depends on the magnitude of the overcurrent (which determines

  respectively the value of the voltage across the terminals

  tive and-negative 42 and 44) and to some extent

  current before the overcurrent condition.

  More particularly, a two-component resistant branch detects the voltage at the positive terminal 42, which is proportional to the current in the load M.

  The potentiometer P 2 allows the calibration of the point of

  trip while the capacitor C 2 filters the

  continuous input to MC 3 switch comparator

  overcurrent delay If the voltage at the

  Tem- switch comparator MC 3 positive input

  overcurrent porization exceeds the reference voltage

  rence V 1, the output of this comparator MC 3 goes to the "open" state. The function of the diode D 8 is to protect the positive inputs of the comparator MC 3 of overcurrent timing switch against excessive input voltages.

  The values of resistance R 9 and of the potentio-

  meter P 2 are adjusted so that the voltage at the positive input terminal of the comparator MC 3 is greater than the voltage at the negative terminal and therefore the

  comparator MC 3 output is in high im

  pedance (open) when the load M is greater than

  percent Therefore, with a charge M lower than

  less than 115 percent, the delay capacitor

  C 6 charges up to an initial voltage which is less than

  lower than the voltage appearing at the positive terminal 42 and may for example not exceed 5 volts, while similarly during a cold start, when the load M is not supplied, the initial voltage

  of the delay capacitor C 6 is zero On the appearance

  rition of an overcurrent condition, the voltage at the positive terminal 42 and therefore at the positive signal input of the comparator MC 3 becomes greater than the reference voltage V 1 and therefore, at the signal input terminal negative of the comparator MC 3. This therefore causes the comparator MC 3 to go to the high impedance state (open). The capacitor C 6 can therefore be charged by a current coming from the diode D 10 and from the resistor R 24 up to at a tension

  which approaches the voltage at positive terminal 42.

  The capacitor C 6 therefore produces the time delay, while representing the thermal capacity of a load,

  for example the temperature of a motor winding.

  In addition, the ignition voltage of the Zener ZD 3 diode

  is chosen so that with a condition of over-

  current exceeding 140 percent of rated load, the Zener ZD 3 diode initiates, allowing the passage of a

  current through branch R 22 This therefore allows an appro-

  exponential ximation in two parts of the time relation I 2 T and therefore a faster charge rate of the capacitor C 6 The values

  components of the timing circuit are calibrated

  abutments so as to produce an actuation of

  about nine seconds trip at 600 percent full load current M, about one minute

  at a full load current of 200 percent and from

  about 3 minutes at a full load current of 125 percent This is graphically depicted on the

  Figure 4 For a given time constant, the values

  their resistors R 22 and R 24 are chosen from ma-

  very high compared to the value of the capacitance of the capacitor C 6 In addition, the value

  of capacitor C 6 is chosen very small because the con-

  main sideration for the choice of the delay capacitor C 6 is a weak relation between the leakage current and the capacity Consequently, the values of R 22 and R 24 can be for example of Il Megohms and 20 Megohms respectively while the value of capacitor C 6 may be for example only 6 microfarads But since very low currents

  charge, which can be of the order of a few nano-

  amps, are used, potential leak circuits must be isolated This is done by means of a certain number of components such as the resistor R 16 which establishes the conditions of load current values for the output terminal of the comparator MC 3 of

  overcurrent delay, and by the clxix of a diode

  of D 12 with low leakage, thus isolating this current source from the delay circuit 50 In addition, input bias currents such as that of the

  comparator MC 7 for tripping by overcurrent

  wind affect the timing and therefore the overcurrent trip comparator MC 7 is also isolated from the rest of the timing circuit

  by the operational amplifier OA 1.

  In addition, uncontrolled impedances of the printed circuit board can intervene in the operation of the circuit and the time delay because these impedances can be for example of the order of 100 to 1000 Megohms, and result from uncontrolled parameters such as the realization of the card, its cleanliness and humidity The effects of these impedances are reduced to a minimum by the guard band 48 which, as already indicated, isolates the critical points of the timing circuit from neighboring voltages on the card.

  circuits Guard band 48 is electrically connected

  ment to the neutral reference branch V 1 so that a comparatively low impedance to ground or a comparatively low impedance cannot appear.

high voltage.

  In the presence of an overcurrent condition, when the voltage of the capacitor C 6 exceeds the reference voltage which is available at the positive terminal of the operational amplifier OA 1, the comparator MC 7 for tripping by overcurrent, normally in the state

2504? 40

  high impedance (open), goes to low impedance, thus grounding the output terminal of MC 7 and allowing the output circuit 52 to de-energize the load M With the output of the comparator MC 7 at low level, the resistors R 27 and R 29 halve the

  voltage at the positive signal input terminal of the

  parateur This action maintains the signal, thus maintaining the tripping condition for the output circuit 52, until the overcurrent condition is eliminated with the delay capacitor C 6 discharged below the voltage at which it was

  percent percent of the nominal load M and generally

  ral, in the present embodiment of the invention,

  five volts Consequently, the rest is delayed

  several minutes and, in this mode of

  reading, about a quarter to a minute Diode D 10

  limits a possible discharge circuit, ensuring the con-

  control of the delay interval while the condensa-

  C 8 ensures insensitivity relative to transi-

  parasitic roofs The Dll diode and the ZD 4 lead diode

  are dimensioned so as to limit the maximum tension

  male which appears at the negative signal input terminal

  ve of the operational amplifier OA 1 and which could damage the components if the voltage across the capacitor C 6 exceeds a safety level for

the operational amplifier OA 1.

  As regards the circuit 28 for phase rupture, as already indicated, - in the case of a phase rupture at load M, the voltage signal which appears at the positive terminal 42 resembles the direct voltage of a single-bridge rectifier The MD 4 comparator for phase-break delay, controlling

  the voltages across the capacitors C 1 and C 2,

  detect this change in waveform and trigger a time delay for the comparator 1 E 8 of the additional trigger switch which also reacts to

  trigger signals from ex-modules

* tiors. Under normal three-phase conditions,

  the voltage appearing at the input terminal of sig-

  negative of the comparator MC 4 of phase break delay is equal to the voltage across the capacitor CI and approaches the voltage at the positive terminal 42, while the voltage appearing at the positive signal input terminal of the comparator MC 4 of phase break delay is equal to the voltage across the capacitor C 2 Since the output of the current transformers CT 1, CT 2-and CT 3 delivers an alternating current, an undulation is propagated by the diodes Dl at D 6 so that the voltage at the positive terminal 42 contains a certain undulation and therefore a minimum and a maximum It is

  this maximum voltage of 100 percent of the load no-

  minimum M as the voltage approaches the input terminal

  of negative signals from comparator MC 4 The minimum voltage

  male is not low enough to allow the

  charge of the peak detection capacitor C1 by the diode D 7 But under phase failure conditions,

  the minimum voltage decreases to the vicinity of the poten-

  earth, allowing the capacitor Ci to discharge by the diode D 7 faster than the voltage across the capacitor C 2 decreases, and it is lower than the voltage detected by the overcurrent and timing circuit Consequently , the voltage appearing at the positive signal input terminal of the timer control comparator MC 4

  phase failure is greater than the signal voltage

  nal negative, equal to the voltage at the input terminal of comparator MC 4, so that the output of the latter

  goes to high impedance state therefore open.

  Zener ZD 1 diode protects signal input terminal

  negative of the MC 4 comparator against any excess voltage-

  sive Resistor R 12 polarizes comparator MC 4 in

zero current conditions.

  With the output of the time comparator MC 4

  open phase break, the capacitor

  Dke timer C 5 is charged by the voltage which appears

  is at the positive terminal 42 The time from the detection of the phase break until the actual tripping of the output circuit is dependent on the intensity of the current in the phase or phases which remain The tripping time is established by resistance

  R 15 which is supplied from the supply voltage

  16 tation V If the phase-breaking current increased the time delay would be accelerated by the

  load comprising resistor R 17 and diode D 9.

  For phase-breaking currents of 50 percent of the nominal load M, the tripping time can be, for example, 30 seconds, while the tripping time with a current of O Opour percent of the nominal load M breaking phase can be for example 20 seconds In addition, the capacitor C 5 serves as a trigger capacitor for external modules which can be connected to the terminal T, charging instantly at a voltage exceeding

  the one that appears at the signal input terminal

  trigger comparator MC 8

  additional In normal mode or without trigger

  the voltage which appears at the input terminal

  positive of MC8 trigger switch comparator

  additional fall is equal to voltage drops

  of D 17, ZD 7 and the base-emitter junction of the transist

  tor T 2 Consequently, if the voltage across the

  densifier C 5 and therefore the voltage which appears at the terminal

  negative signal input of comparator MC 8

  additional trigger mutator exceed the

  voltage drop due to diodes D 17, ZD 7 and transistors

  tor T 7, the output of the comparator MC 8 being normal-

  in the high impedance (open) state changes to

  low impedance, connecting the output terminal to ground.

  This produces a trigger signal for the stage of

04748

  output 52 When the trigger signal is produced, the voltage at the positive signal input terminal of the comparator MC 8 is reduced to the voltage drop of the diode D 17, generally 0.6 Volt This voltage reduction at the terminal positive of MC 8 comparator main-

  holds the trigger signal until -i condi-

  trigger condition is eliminated and the condensa-

  time delay C 5 is discharged unless the voltage drop of the diode D 17 The delay of the voltage drop is also controlled by the value of the resistor R 21, this delay being all the longer as the value of this resistance is higher so that if the resistance R 21 is for example 900 kilohms, this results in delay of 1.25 minutes while for example if the resistance R 21 is chosen with a lower value, for example 15 kil 4> hms, setting

  at rest is not delayed at all but in fact instantaneously

  tanned. With regard to the ground fault circuit 24, Fig 1 A is a diagram of this circuit It is understood that the fault circuit 24 to

  the earth can be integrated with the circuits of the dispo-

  load protection device, but in the present embodiment of the invention, it consists of a module 24 shown in FIG. 2 and which can be plugged in as shown in FIG. 5 In the absence of a fault in the earth, the phase currents in

  the lines L1, L 2 and L 3 of FIG. I are equal in in-

  1200 phase shift and phase shift Continuous output of the cap-

  current generator 14 contains a ripple amplitude of from about 140 to about six times the frequency of the source and, in the present embodiment, a

  source of approximately 60 Hz produces a wave frequency

  tion of 360 Hz In addition, in the absence of a ground fault in the load M, the vector sum of the phase currents in the load and therefore the vector sum of the currents in the transformer secondary of the branch neutral GF of Fig 1

  is zero Therefore, no current flows

  flows through the resistor Ri and the voltage drops across the resistor R 2 and the potentiometer Pl

  can be equal (see Figure 1) When a disturbance

  ment to earth occurs, the vector sum of the currents in the three phases of the load M N is more

  equal to zero It follows that a residual current circ

  flows in the resistor RI of Fig 1 towards the neutral branch GF At the same time as a current in the resistor Ri, there appear unequal currents in the resistor R 2 and the potentiometer Pi It is understood that the resistor R 1 can be for example a short circuit because its main function is to present a circuit in the neutral branch during a ground fault condition In this ground fault condition, a current flows through the resistor RI and the voltage across the terminals of R 2 is different from that at the terminals of the potentiometer Pi Consequently, the potential voltage of the terminal GF is no longer about half

  23 of the voltage of terminals "+" and "-" 40, 44 With this ni-

  voltage calf at terminal GF less than half the voltage at positive and negative terminals 42 and 44, the voltage at the negative signal input terminal of comparator MC 1 of earth fault sensor is greater than the voltage at the positive terminal of this

  MCI comparator, from which it follows that the sig-

  comparator output signals MC 1 is grounded The comparator ground output signal terminal

  MCI or MC 2 results in a discharge to the mass of the conden-

  sator C 3 which is normally charged essentially at voltage V Consequently, comparator MC 5 of K ground fault delay time receives at

  its positive signal input terminal an essential voltage

  tially equal to the starting voltage of the Zener diode ZD 2, greater than the voltage of the input terminal

  therefore, the output of the com-

  MC 5 parator is in the high impedance or open state This allows the capacitor C 4 to charge up to a voltage which exceeds the ignition voltage of the Zener ZD 2 diode and therefore the voltage of the comparator MC 6 positive signal input terminal for earth fault delay is higher than

  lower than the voltage of the negative signal input terminal

  tive of this same comparator The output signal terminal

  tie of MC 6 is therefore in a high impedance (open) state.

  This allows the voltage VK at terminal K to circulate

  ler a current in the diode D 15 towards the terminal of

  trip T, thus causing the comparator MC 8 of the additional trip switch of the

  Fig 1 starts a trigger sequence and desali-

  lie the load M The value of the Zener ZD 5 diode is

  chosen to ensure the start of the sequence of

  Zener ZD 5 diode must have a voltage

  over the voltage appearing at the terminal

  ne positive signal input comparator MC 8 additional trigger switch Voltage

  applied in addition to the starting voltage of ZD 5 entral-

  do the priming of the rectifier grid controlled if

  licium SCI 1, allowing the passage of a current and to the

  LED 1 to indicate that a trip

  earth disturbance occurred The setting

  at rest the protective device is done in the manner

  re described below, either automatically or manually-

  is lying. In normal mode, when no earth fault is present, the output of the earth fault delay comparator MC 6 is at

  ground, short-circuiting the voltage VK pro-

  amalgamating a current in the resistor R 23, so as not to allow a current to flow through the diode D 15 or the Zener diode ZD 5, to remove the supply of the grid of the rectifier SC 1 In addition, in the mode of

  put to rest on opening the momentary contact of the

  mutator SW 1, the voltage is removed from terminal K thus stopping the circulation of a current in the rectifier controlled with silicon SCI, which extinguishes the light-emitting diode LED 1 The potentiometer P 3 determines the percentage of fault current to earth which is allowed before authorizing the change of state of the comparators MC 1 or MC 2 In addition, the Zener diode ZD 2 determines the voltage and therefore the percentage of load of the motor IL for which the delay comparator MC 5 disturbance to

earth is unlocked.

  The test circuit 56 makes it possible to check the

  overcurrent and delay circuit 50 in the ab-

  sence of an overcurrent condition in the load

  M, or without using an external test device.

  Resistor R 14 is dimensioned so that

  in the normal quiescent current control mode,

  when the load M is not in overcurrent condition

  sity, the effect of adding the resistor R 4 is minimized This is due to the low impedance of the load resistor 22, which has been mentioned

  previously that it was in the range of 60 to 600 Ohms.

  When removing the calibration socket 22 or another module, such as that shown in FIG. 2,

  the impedance of the increased current detection circuit 14

  lies down to a value which is about 5.5 times

  that of the resistance R 14 Since the resistance

  tance R 14 is supplied by the supply voltage

  VKI the voltage which appears at the positive terminal 42

  passes the one which should appear at load resistance 22 if load M received a nominal current of 100% This therefore simulates an overcurrent condition

  so that the overcurrent and time circuit 50

  porization begins to trigger a tempo sequence

  This sequence takes place in the same way as that already mentioned for an actual overcurrent condition. The resistor R 14 is designed to simulate a current representing 125 percent of the current at full load of the motor M, so that the load M is disconnected from the source in approximately 3 minutes, as shown in Figure 4 The M load is re-energized in the output circuit 52 and continues so as to cause tripping, thus de-energizing the load M , until the load resistance module 22 is again plugged into the load protection device. With regard to the output circuit 52, upon production of a trigger signal by the

  overcurrent and delay circuit 50, the circuit

  cooked 28 of phase break or by the appearance of a trigger I signal at terminal T, coming for example from the earth fault circuit 24, the relay control transistor T 2 and therefore

  the output relay RE 1 are de-energized, thus eliminating

  if the supply of the load M Simultaneously with the

  de-energization of relay RE 1, the light-emitting diode-

  cente LED 1 and blocking circuit transistor T 1 are energized Connection switch Si indicates

  if the unit automatically returns to idle or requires

  site a manual standby, by the fact that the voltage source at the base of the control transistor T 2

  relay is connected in series with switch 51.

  In the normal energized state, when power is applied to the load M, the base current of the relay control transistor T 2 is

  provided by the resistor R 31 and the Zener diode ZD 7.

  With transistor T 2 on, the control relay

  RE 1 is excited now closed its working contacts

  vail With the transistor T 2 saturated, the basic drive of the blocking control transistor T 1 is derived to ground by the diode D 20, thus keeping the light-emitting diode LED 2 off The resistor R 36

  base of transistor T 1 ensures the state of this transistor

  tor when transistor T 2 is turned on.

  If the output terminal of the overcurrent trip comparator MC 7 or of the additional trip switch MC 8 comparator

  goes low, going to ground, attacking

  that basic relay control transistor T 2 is short-circuited to ground The use of the diode D 16 ensures that the voltage required to change

  of the operational amplifier OA 1 and therefore

  sequence the state of the comparator MC 7 tripping by overcurrent is not affected by a change of state of the output circuit 52 This action therefore allows

  the comparator MC 7 or MC 8 which caused the trip-

  controls the duration of the delay before being put to rest.

  The automatic-manual SI switch can be a

  two-position unipolar mutator or an internal connection point in the diagram of FIG. I and, in the present embodiment of the invention, it is a connection point In the manual configuration, the time which runs out before being put to rest

  after de-energization of the REI relay can be instantaneous

  born for trigger conditions caused by

  the comparator MC 8 of the trigger switch

  additional, or longer, for example 1.25 minutes for trips caused by the overcurrent trip MC 7 comparator The reason for the delay

  before resting when an over-trip

  intensity appears St, is that it is necessary to allow the load

  M to cool down after an overheating condition.

  During the operation of the REI relay, the diode D 21 prevents damage to the semiconductor components

  associated During the time when the transistor T 2 of

  relay command is blocked, the basic drive current for the blocking control transistor TI is supplied by the resistor R 35, enabling the transistor TI as well as the light-emitting diode indicator LED 2 to be released. Zener diode ZD 8 provides a secondary conduction circuit if the LED indicator 2 fails In the manual configuration, this action is maintained automatically so that the basic driving current of the relay control transistor T 2 is supplied by the voltage drop at the junction between the current limiting resistor R 30 and the anode of the light-emitting diode LED 2.

  The Zener diode ZD 7 and the basic resistor R 32 of the tran-

  sistor T 2 ensure that the tripping state is maintained until the supply of the output circuit 52 is interrupted, using the momentary switch SW 1 If before the actuation of the switch SW 1, the tripping comparator MC 7 by overcurrent and the comparator MC 8 of additional trip switch are not in trip condition,

  when power is restored, the attack current

  that basic transistor T 2 is restored, and therefore

  quent, the output relay RE 1 is energized and closes its contacts If the comparator MC 7 or the compartment MC 8 is in tripping state when the switch SW 1

  is operated, the basic attack current of the transist

  tor T 2 is again earthed, now de-energized the output relay RE 1 and now released

  the transistor T 1 and the light-emitting diode LED 2.

  Zener ZD 11 diode inhibits the LED indicator

  luminescent LED 2 and the transistor T 1 for blocking control

  cage when the supply voltage V is less than K at around 75% of the ignition voltage of the Zener ZD 9 and ZD 10 diodes This ensures that when the supply

  is applied, the unit does not go into the trip state

  unless the delay necessary for the

  rest has elapsed The capacitor Cll reduces the

  sensitivity of the unit to parasites.

  In the automatic mode of switch 51, the basic driving current of the control transistor T 2

  relay is supplied by the supply voltage VK.

  When the state of one of the MC 7 or MC 8 trip comparators returns to normal, cut-off condition,

  the basic drive current is restored for the tran

  sistor T 2 without operator intervention, thus exciting the control relay RE 1 which closes its associated working contacts, and blocking the transistor Tl and

  LED light-emitting diode indicator 2.

  It is understood that the device according to the invention can control loads other than

  motors such as transformers or power sources

  without departing from the framework or the spirit of the information

  In addition, it is understood that a circuit breaker can be used at the contactor plate or that the output circuit can trigger an audible signal and '

  or a visual alarm instead of or in place of the contact

  It is further understood that the comparators

  that are part of integrated circuits can be arranged

  in different combinations on integrated circuits, or be combined in integration circuits

  thrust or even consist of discrete components.

  In addition, the level or duration of the disturbance conditions-

  before triggering can be increased or di-

  minué In addition, other modules which have not been men-

  explicitly mentioned may use this provision and may include for example long modules

  acceleration, phase imbalance modules, uti-

  reading the arrangement of the pins according to the invention.

  Therefore, in addition to the advantages mentioned

  above, the invention which has been described provides a dis-

  load protection positive which is compact, with

  modular expansion possibilities, while

  killing an effective load protection device The invention thus relates to a load protection device which closely coordinates the load protection

  with detection of fault conditions.

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LEGEND N REF FIGURE

EXIT CONTACT F 27 3

PHASE BREAK DETECTION 28 2

ACCESSORY MODULE 30 2

ACCESSORY MODULE 30 '2

OUTPUT SWITCH 38 2

OUTPUT SWITCH 38 2 A

Claims (4)

  1 Load protection device   to protect an electrical circuit against over-   intensities, characterized in that it includes a provision   sensor device (14) intended to detect a current which circulates in an electric circuit, this sensor device producing an output signal which is function   of said current flowing, a device (26) for   reverse time charge connected to said device cap-   tor and intended to detect the thermal state of said   charge, producing a signal for a de-   circuit control trip, the latter signal being produced at an instant which is a function of the state   of said load, a condensing device   tor connected to said reverse time overload device, comprising a device for raising the voltage level in said capacitor device as a function of the thermal state of said load and a circuit control trigger device (38), connected to said device of reverse time overload and to said electrical circuit to control this circuit   when said last signal is produced.   2 Protection device according to resale   dication 1, characterized in that said circuit control trigger device (38) opens or closes said electrical circuit.   3 Protection device according to resale   dication 1, characterized in that said circuit control trigger device (38) opens or closes said electrical circuit.   4 Protection device according to resale   dication 2, characterized in that the voltage level of said storage device allows said reverse time overload device to open or close said electrical circuit.