EP3806127B1

EP3806127B1 - Control system and method for an electromechanical contactor of a power circuit

Info

Publication number: EP3806127B1
Application number: EP19382882.9A
Authority: EP
Inventors: Enric SALA MASIP
Original assignee: Fico Triad SA
Current assignee: Fico Triad SA
Priority date: 2019-10-08
Filing date: 2019-10-08
Publication date: 2023-06-14
Anticipated expiration: 2039-10-08
Also published as: EP3806127A1; CN112631362A

Description

Field of the invention

The invention relates to a control system and a method for an electromechanical contactor of a power circuit which results in a reduction in power consumption in the coils of said electromechanical contactor. Electromechanical contactors are used in many applications, for instance, in electric vehicles.

Background of the invention

For the connection and disconnection of power circuits, electromechanical contactors are typically used. Such electromechanical contactors comprise two parts, a contact and a coil.
The contact can be moved to one direction that produces the connection (ON) of the power circuit or it can be moved in an opposite direction to produce the disconnection (OFF) of the power circuit.
The coil is a kind of electromagnet that produces a mechanical force to move the contact. The mechanical coupling between the coil and the contact is provided by an internal shaft and a spring.
In the disconnected (OFF) state, the coil is not energized, and the shaft is moved or maintained in the disconnection position due to the spring force. In the connected (ON) state, the coil is energized, and the applied force overcomes the force of the spring that moves the contact to the connected position.
Therefore, when the contactor is in the ON state, i.e., connected to the power circuit, the coil requires power to be applied.
Energy saving is especially relevant when contactors must remain in an ON state for a long period of time as, for example, in electric vehicle applications.
In the OFF state, the magnetic circuit is open. When the contactor is to be closed, a strong force, named as "pick-up" force, must be applied to start the shaft movement. After displacement, the magnetic circuit remains closed and it is no longer necessary to apply such a strong force to keep the contact in the closed position, named as "holding" force.
Accordingly, during the "pick-up" stage, a relatively strong electrical power must be applied to the electromagnetic coil but, later, during the "holding" stage, it is not necessary to maintain such a high power applied to the coil.
In a typical application, a power supply is used to provide the energy to the contactor coils. A low voltage (i.e. 12 Vdc) power supply is used in many applications.
The low voltage power supply is often implemented by a kind of DC power converter (i.e. buck, boost, sepic, or other topologies) providing a fixed, stabilized constant voltage in order to drive the contactor coils to prevent possible voltage fluctuations from closing the contactor when it should not.
In order to reduce the electric power consumption in the coil during the "holding" state, some techniques have been used.
It is known to use dual coil contactors. In this case, the contactor is built with two internal coils, one optimized for the "pick-up" conditions, and, another optimized for the "holding" conditions. An electronic circuit switches the coils when necessary to economize. This solution is expensive due to the dual coil and the switching circuit.
It is also known to use resistor voltage dividers as can be seen in figure 1. During the "holding" stage, in order to reduce the current through the coil (2), some resistors (10) are electrically connected in series with the coil (2). During the "pick-up" state, the resistors (10) are by-passed with a switching circuit (11). This solution is expensive due to the use of resistors (10) connected in series with the coil (2) and the required switching circuit (11). Resistors (10) are power resistors in order to stand to be in series with the coil (2) and to resist the intensity that would circulate through them. In addition, part of the power dissipation is transferred to the resistors (10), decreasing the efficiency of the economization. Moreover, this type of resistors (10) dissipate heat to the surrounding electronics, which is not convenient, and they also need space to be located.
Finally, it is also known to use Pulse Width Modulation (PWM) techniques as shown in figure 2. During the "pick-up" stage, the coil (2) is driven at 100% of the voltage, thus applying high power. During the "holding" stage the coil (2) is driven to a reduced duty cycle (i.e. 50%) to reduce to average energy applied to the coil (2). This is implemented by the PWM, driving ON and OFF at high speed.
Due to the high frequency applied to the contactor and the high quantity of switch ON and switch OFF cycles, this solution produces electromagnetic interference (EMC) into the surrounding circuits and is not recommended in a safe environment.
It is known document EP1009006 A1 disclosing a command mechanism for opening or closing of a circuit breaker having a microprocessor controlling a switch in series with a coil. The microprocessor compares the command level against thresholds. A first voltage is compared with a first and second level, distinct from a lower level controlling the coil during the command phase for a predetermined time.

Summary of the invention

The present invention is a control system and a method for an electromechanical contactor of a power circuit that reduces power consumption, thus economizing energy. The invention is based on a voltage regulated power supply.
As previously stated, known electromechanical contactors of a power circuit comprise:

a contact, movable between two positions:
- an open position in which the contact produces the disconnection of the power circuit, and
- a closed position in which the contact produces the connection of the power circuit,
a coil, in mechanical connection with the contact and configured to drive the contact between the above open and closed positions.

The control system also comprises a regulated power supply. The regulated power supply is connectable to the coil and is configured to provide a constant regulated output voltage V_OUT to the coil. The regulated power supply is also configured to receive a feedback voltage V_FBK having a k relationship with the output voltage V_OUT, V_FBK = V_OUT * k. The regulated power supply is configured to modify the provided output voltage V_OUT when the feedback voltage V_FBK received by the power supply differs from a reference voltage V_REF.
The control system further comprises a controller adapted to be connected to the regulated power supply. The controller is configured to vary the relationship k between the output voltage V_OUT and the feedback voltage V_FBK from at least a first relationship k₁ to a second relationship k₂, being k_{2 >} k₁. Accordingly, the regulated power supply varies the provided output voltage V_OUT between at least a first output voltage V_OUT1 and a second lower output voltage V_OUT2 for reducing power consumption of the coil.
Therefore, as the relationship k is varied from k₁ to k₂, the feedback voltage V_FBK received by the regulated power supply also varies from a first feedback voltage V_FBK1 to a second feedback voltage V_FBK2. Said variation occurs while the output voltage V_OUT remains the same, as it is not varied, being the first initial output voltage V_OUT1 for both feedbacks voltages. The second feedback voltage V_FBK2 is greater than V_FBK1. Said second feedback voltage V_FBK2 differs from the reference voltage V_REF and an error exists.
Thus, the regulated power supply receives for the first initial output voltage V_OUT1 a second feedback voltage V_FBK2 different from the reference voltage V_REF Therefore, the regulated power supply initiates a regulation iterative process modifying the output voltage V_OUT until the received feedback voltage V_FBK is equal to the reference voltage V_REF and thus the error is zero. When a stable position is reached again, i.e., V_REF = V_FBK, V_OUT has been modified to a second out voltage V_OUT2, according to the relationship k₁/k₂.
As the second output voltage V_OUT2 is lower than the first output voltage V_OUT1, a reduction in the power consumption of the coil is achieved by controlling the provided output voltages.
Therefore, the control system of the invention makes use of the existing power supply, specifically a regulated power supply adapted to provide a constant output voltage V_OUT. The control system is therefore able to make the power supply to switch between, for instance, two different voltage settings, a first and a second output voltages V_OUT by providing the power supply with a different relationship k between the output voltage V_OUT and the feedback voltage V_FBK.
According to the regular operation of a regulated power supply, it compares the received second feedback voltage V_FBK2 with the fixed reference voltage V_REF and any difference is used to modify the output voltage V_OUT of the power supply in such a way as to reduce the voltage error and to receive the settled feedback voltage V_FBK.
Thus, the controller "deceives" the regulated power supply, by manipulating the relationship k between the output voltage V_OUT and the feedback voltage V_FBK, i.e., V_FBK = V_OUT * k, so that the regulated power supply receives a modified feedback signal, such that the regulator "believes" that the regulated power supply is out of its working point and reacts looking for another output voltage value.
Thus, the regulation cycle is performed by the regulated power supply itself and therefore it has the advantage that the invention can be applied on an existing regulated power supply.
More specifically, as the closed position of the contact comprises two stages, a first pick-up stage and a second holding stage, the controller is configured to provide:

the first relationship k₁ in the pick-up stage of the contact so that the regulated power supply is configured to provide the first output voltage V_OUT1, and
the second relationship k₂ in the holding stage of the contact so that the regulated power supply is configured to provide the second lower output voltage V_OUT2. Said second relationship k₂ may be provided at the beginning of the holding stage or after a period of time from the beginning.

In an embodiment, the power supply comprises a voltage regulator configured to make the power supply to provide the constant output voltage V_OUT to the coil. The voltage regulator comprises:

means for receiving a feedback voltage V_FBK,
means for comparing the received feedback voltage V_FBK with the reference voltage V_REF,
means for making the regulated power supply to vary the provided output voltage V_OUT if the received feedback voltage V_FBK differs from the reference voltage V_REF in order to provide a constant output voltage V_OUT to the coil (2).

It is also an object of the invention a control method for an electromechanical contactor of a power circuit, the electromechanical contactor comprising:

a contact, movable between two positions:
- an open position in which contact produces the disconnection of the power circuit, and
- a closed position in which the contact produces the connection of the power circuit,
a coil, in mechanical connection with the contact, and configured to drive the contact between the open and the closed positions.

The control method comprising the step of providing a regulated power supply connectable to the coil. The regulated power supply configured to provide a constant regulated output voltage V_OUT to the coil and to receive a feedback voltage V_FBK having a k relationship with the output voltage V_OUT, V_FBK = V_OUT * k. According to the regulated nature of the power supply, it will modify the provided output voltage V_OUT when the feedback voltage V_FBK received by the power supply differs from a reference voltage V_REF and therefore an error exists.
The method additionally comprises the step of providing a controller, the controller varying the relationship k between the output voltage V_OUT and the feedback voltage V_FBK from at least a first relationship k₁ to a second relationship k₂, being k_{2 >} k₁, such that the regulated power supply varies the provided output voltage V_OUT from at least a first output voltage V_OUT1 to a second lower output voltage V_OUT2 for reducing power consumption of the coil.
Therefore, as the relationship k is varied from k₁ to k₂, the feedback voltage V_FBK received by the regulated power supply also varies from a first feedback voltage V_FBK1 to a second feedback voltage V_FBK2. As previously stated, said variation occurs while the output voltage V_OUT remains the same, as it is not varied, being the first initial output voltage V_OUT1 for both feedbacks voltages. The second feedback voltage V_FBK2 will be greater than V_FBK1. Said second feedback voltage V_FBK2 differs from the reference voltage V_REF and an error exists and, therefore, the regulated power supply initiates an iterative process to provide a constant output voltage V_OUT.

Description of the figures

To complete the description and in order to provide for a better understanding of the invention, drawings are provided. Said drawings form an integral part of the description and illustrate a preferred embodiment of the invention. The drawings comprise the following figures.

Figure 1 shows a known electric circuit of an electromechanical contactor comprising a system configured to reduce power consumption according to the state of the art.
Figure 2 shows a known electric circuit of an electromechanical contactor comprising a system configured to reduce power consumption according to the state of the art.
Figure 3 shows a block diagram of the regulation system according to an embodiment of the invention.
Figure 4 shows an implementation of an electric circuit of the electromechanical contactor of the invention.
Figure 5 shows a voltage-time diagram, a power-time diagram and switch-time and coefficient or factor-time diagrams for the embodiment of figure 4.

Detailed description of the invention

Figure 3 shows a block diagram of a control system of an electromechanical contactor according to an embodiment of the invention. The control system comprises:

a contact (1), movable between the open and closed positions,
a coil (2), in mechanical connection with the contact (1) and configured to drive the contact (1) between the open and the closed positions,
a regulated power supply (3), connectable to the coil (2), the regulated power supply (3) configured to provide an output voltage V_OUT to the coil (2).

As previously stated, the regulated power supply (3) is configured to provide a constant regulated output voltage V_OUT to the coil (2) and to receive a feedback voltage V_FBK having a relationship k with the output voltage V_FBK = V_OUT * k. According to the regulated nature of the power supply (3), it is configured to modify the provided output voltage V_OUT when the feedback voltage V_FBK received by the power supply (3) differs from the reference voltage V_REF.
In the shown embodiment of figure 3, the feedback voltage V_FBK received by the power supply (3) is V_FBK = V_OUT * k being the value of the relationship k controlled by the controller (4). Thus, the controller (4) is configured to act over the relationship k, in turn, this modifying the feedback voltage V_FBK value.
In an embodiment, the controller (4) is configured to switch between the first relationship k₁ and the second relationship k₂ after a fixed period of time.
Considering an embodiment in which the regulated power supply is settled with a relationship k between V_OUT and V_FBK equal to 1. The controller (4) will provide a first relationship k₁ during the pick-up stage and a second relationship k₂ during the holding stage.
According to this, in said embodiment and with the following default conditions:

V_REF=12 Vdc
V_ERR=0 in stable conditions
V_REF = V_FBK as expected in stable operation of the electromechanical contactor, with an error voltage V_ERR=0.
V_FBK = V_OUT * k which is the feedback voltage received by the voltage regulator (6),
V_OUT = V_FBK / k which is the output voltage that will be provided by the regulated power supply, but as V_REF = V_FBK, in a stable operation, thus $V_{OUT} = V_{REF} / k .$

Accordingly, with a stable voltage reference V_REF, the output voltage V_OUT can be modified by applying different values to the relationship k.
In stable conditions, it has to be considered that the error voltage V_ERR must be equal to 0. According to the above, the regulated power supply (3) will provide a different voltage if the feedback voltage V_FBK received differs from the reference voltage V_REF.

Pick-up state:

The system is stable with the following conditions:

V_REF = 12 Vdc
V_OUT = 12 Vdc
k₁ = 1
V_FBK = 12 Vdc
V_ERR = 0

With the "pick-up" conditions the controller (4) can drive the switch (5) with the maximum voltage/energy applied to the contactor-coil (1, 2). Furthermore, applying a relationship k₁ = 1, the output voltage V_OUT will be the same as V_REF, in this example 12 Vdc.

Holding State:

In an embodiment, the electromechanical contactor has an actuation time to close the contact (1), for instance 50 ms, the controller (4) waits for a longer time, for instance 300 ms, to provide a different relationship k.
Thus, after a short time, the controller (4) provides a relationship k_{2 >} k₁.
In the following embodiment a relationship k₂ which is double of k₁ is provided so that the output voltage V_OUT is reduced to the half in stable conditions.

V_REF = 12 Vdc
V_OUT2 = 6 Vdc (when the stable conditions are reached)
k₂ = 2
V_FBK = 12 Vdc (when the stable conditions are reached again)
V_ERR = 0

With the "holding" conditions, the controller (4) drives the switch (5), but the energy applied to the contactor-coil (1, 2) would be reduced. In this embodiment, applying a relationship k₂ of 2, the output voltage V_OUT will be half the voltage of V_REF, i.e., 6 Vdc.
It is possible to implement other values of the relationship k to adjust the output voltage V_OUT, according to the particular "holding" conditions of different contactors with different "holding" requirements. For instance, under normal conditions, for the output voltage V_OUT of the power supply, the feedback voltage V_FBK is considered to be between 0 V and 1 V.
In figure 4, an embodiment of the implementation of an electric circuit of the electromechanical contactor of the invention is depicted in which how the relationship k is implemented is shown.
Specifically, the control system comprises a voltage divider connected to the output of the regulated power supply (3) comprising a set of resistors (R3, R4, R5) located in series. The set of resistors (R3, R4, R5) located in parallel with the coil (2). The controller (4) is configured to switch on and off one of the resistors, resistor R3, so that the relationship between the feedback voltage V_FBK and the output voltage V_OUT, i.e., k, can be varied by the controller (4).
In this embodiment, the voltage of (R4 + R3) / (R5 + R4 +R3) x V_OUT is the feedback voltage V_FBK provided to the regulated power supply (3), wherein R3 could be 0 or R3.
As previously stated, figure 4 discloses an implementation of the claimed system. The output voltage V_OUT is measured by a combination of resistors R3, R4, R5 acting as voltage dividers and the measurement is sent to the voltage regulator (6) of the power supply (3) through the feedback connection.
When a NOT_ECONOMIZE output is activated, a transistor Q2 overrides resistor R3 and the feedback signal changes accordingly.
When the power supply (3) see other value in V_FBK than the real V_REF, it tries to compensate the voltage through its internal regulation, modifying the output voltage V_OUT, until the V_FBK signal is equal to V_REF, arriving to the desired V_OUT for the holding stage.
In this embodiment, depending on the values of the resistors R3, R4, R5, two stable output voltages may be provided, one depending on R4/(R4+R5) and another depending on (R3+R4)/(R3+R4+R5).
Said resistors are therefore outside the main circuit of the coil (2) activation, and are small polarization resistors, negligible in cost and they do not produce additional heat and need little space.

Claims

Control system for an electromechanical contactor of a power circuit, the electromechanical contactor comprising:
• a contact (1), movable between two positions:
- an open position in which the contact (1) produces the disconnection of the power circuit, and

- a closed position in which the contact (1) produces the connection of the power circuit,

• a coil (2), in mechanical connection with the contact (1) and configured to drive the contact (1) between the open and the closed positions,

characterised in that the control system comprises a regulated power supply (3) connectable to the coil (2), the regulated power supply (3) configured to provide a constant regulated output voltage V_OUT to the coil (2) and to receive a feedback voltage V_FBK having a k relationship with the output voltage V_OUT, V_FBK = V_OUT * k,

the control system further comprises a controller (4), the controller (4) being configured to vary the relationship k between the output voltage V_OUT and the feedback voltage V_FBK from at least a first relationship k₁ to a second relationship k₂, being k_{2 >} k₁, such that, the regulated power supply (3) varies the provided output voltage V_OUT from at least a first output voltage V_OUT1 to a second lower output voltage V_OUT2 for reducing power consumption of the coil (2).
Control system for an electromechanical contactor of a power circuit, according to claim 1, wherein the closed position of the contact (1) comprises two stages, a first pick-up stage in which the contact (1) starts to move to close the power circuit and a second holding stage in which the contact (1) is closed with the power circuit connected, the controller (4) being configured to provide:
- the first relationship k₁ in the pick-up stage of the contact (1) so that the regulated power supply (3) is configured to provide the first output voltage V_OUT1, and

- the second relationship k₂ in the holding stage of the contact (1) so that the regulated power supply (3) is configured to provide the second lower output voltage V_OUT2.
Control system for an electromechanical contactor of a power circuit, according to any preceding claim, wherein the regulated power supply (3) comprises a voltage regulator (6) configured to make the regulated power supply (3) to provide the constant output voltage V_OUT to the coil (2).
Control system for an electromechanical contactor of a power circuit, according to claim 3, wherein the voltage regulator (6) comprises:
- means for receiving the feedback voltage V_FBK,

- means for comparing the received feedback voltage V_FBK with the reference voltage V_REF,

- means for making the regulated power supply (3) to vary the provided output voltage V_OUT if the received feedback voltage V_FBK differs from the reference voltage V_REF such that a constant output voltage V_OUT is provided to the coil (2).
Control system for an electromechanical contactor of a power circuit, according to any preceding claim, wherein the control system comprises a voltage divider connected to the output of the regulated power supply (3) providing a feedback to it (3).
Control system for an electromechanical contactor of a power circuit, according to claim 5, wherein the voltage divider comprises a set of resistors (R3, R4, R5) located in series, the set of resistors (R3, R4, R5) located in parallel with the coil (2), the controller (4) being configured to switch on and off at least one of the resistors R3 for varying the relationship k between the output voltage V_OUT and the feedback voltage V_FBK.
Control system for an electromechanical contactor of a power circuit, according to claim 6, wherein the control system further comprises a transistor Q2 configured to be connected with one of the resistors (R3) and with the controller (4), being the controller (4) configured to override said resistor (R3) through the transistor Q2.
Control system for an electromechanical contactor of a power circuit, according to claim 6 or 7, wherein the voltage of resistor R3 and R4 is the feedback voltage V_FBK provided to the regulated power supply (3).
Control system for an electromechanical contactor of a power circuit, according to any preceding claim, wherein the controller (4) is configured to switch between the first k₁ and the second k₂ relationship after a fixed period of time from the connection of the power circuit.
Control system for an electromechanical contactor of a power circuit, according to any preceding claim, wherein the voltage regulator is a DC power converter.
Control method for an electromechanical contactor of a power circuit, the electromechanical contactor comprising:
• a contact (1), movable between two positions:
- an open position in which contact (1) produces the disconnection of the power circuit, and

- a closed position in which the contact (1) produces the connection of the power circuit,

• a coil (2), in mechanical connection with the contact (1), and configured to drive the contact (1) between the open and the closed positions,

characterised in that the control method comprises the step of providing a regulated power supply (3) connectable to the coil (2), the regulated power supply (3) configured to provide a constant regulated output voltage V_OUT to the coil (2) and to receive a feedback voltage V_FBK having a k relationship with the output voltage V_OUT, V_FBK = V_OUT * k,

the method comprises the step of providing a controller (4) the controller (4) varying the relationship k between the output voltage V_OUT and the feedback voltage V_FBK, from at least a first relationship k₁ to a second relationship k₂, being k_{2 >} k₁, such that the regulated power supply (3) varies the provided output voltage V_OUT from at least a first output voltage V_OUT1 to a second lower output voltage V_OUT2 for reducing power consumption of the coil (2).
Control method for an electromechanical contactor of a power circuit, according to claim 11, wherein it comprises the step of adding a voltage divider connected to the output of the regulated power supply (3) and providing a feedback to it (3).
Control method for an electromechanical contactor of a power circuit, according to claim 12, wherein the voltage divider comprises a set of resistors (R3, R4, R5) located in series, the set of resistors (R3, R4, R5) located in parallel with the coil (2), the controller (4) switching on and off at least one of the resistors R3 for varying the relationship k between the output voltage V_OUT and the feedback voltage V_FBK.
Control method for an electromechanical contactor of a power circuit, according to claim 13, wherein further comprises the step of adding a transistor Q2 connected with one of the resistors (R3) and with the controller (4), the control method comprising the step of the controller (4) overriding said resistor (R3) through the transistor Q2.