阅读说明：本技术 控制方法、控制系统以及电动泵 (Control method, control system, and electric pump ) 是由 不公告发明人 于 2019-03-28 设计创作，主要内容包括：本发明公开了一种控制方法、控制系统以及电动泵,控制系统能够控制电动泵,电动泵的当前电流处于第一区间,并且电动泵的当前转速大于或等于第一设定转速,判定电动泵处于干转状态；这样利用电流和转速作为判断依据能够有利于判定电动泵的运作状态。(The invention discloses a control method, a control system and an electric pump, wherein the control system can control the electric pump, the current of the electric pump is in a first interval, and the current rotating speed of the electric pump is greater than or equal to a first set rotating speed, so that the electric pump is judged to be in a dry-running state; thus, the use of the current and the rotation speed as the judgment basis can facilitate the judgment of the operating state of the electric pump.)

1. A control method capable of controlling an electric pump, defining a first limit current and a second limit current, the first limit current, the second limit current increasing with an increase in a rated voltage of the electric pump; wherein the first limiting current is less than the second limiting current; defining a set of current values between the first limiting current and the second limiting current as a first interval; judging the relation between the current of the electric pump and the first interval, if the current of the electric pump is in the first interval, judging the relation between the current rotating speed of the electric pump and a first set rotating speed, and if the current rotating speed of the electric pump is greater than or equal to the first set rotating speed, the electric pump is in a dry rotation state; and when the electric pump is in a dry-running state, controlling the electric pump to stop running, or controlling the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed, wherein the limited rotating speed is greater than the minimum rotating speed and less than the maximum rotating speed.

2. The control method according to claim 1, characterized in that a relationship between a current rotation speed of the electric pump and the first set rotation speed is judged, a relationship between a current voltage of the electric pump and a first set voltage is judged if the current rotation speed of the electric pump is less than the first set rotation speed, and the electric pump is in a dry running state if the current voltage of the electric pump is less than or equal to the first set voltage; if the current voltage of the electric pump is greater than the first set voltage, the electric pump is in a non-dry-running state; and when the electric pump is determined to be in a non-dry rotation state, controlling the rotation speed of the electric pump to be kept unchanged.

3. The control method according to claim 1 or 2, characterized by defining a third limiting current, wherein the third limiting current is greater than the second limiting current, defining a set of current values between the second limiting current and the third limiting current as a second interval; judging the relation between the current of the electric pump and the second interval, if the current of the electric pump is in the second interval, judging the relation between the current rotating speed of the electric pump and a second set rotating speed, and if the current rotating speed of the electric pump is less than the second set rotating speed, the electric pump is in a dry rotation state; and when the electric pump is in a dry-running state, controlling the electric pump to stop running, or controlling the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed, wherein the limited rotating speed is greater than the minimum rotating speed and less than the maximum rotating speed.

4. The control method according to claim 3, characterized in that a relationship between the current rotational speed of the electric pump and the second set rotational speed is judged, a relationship between the current voltage of the electric pump and a second set voltage is judged if the current rotational speed of the electric pump is greater than or equal to the second set rotational speed, and the electric pump is in a dry-running state if the current voltage of the electric pump is greater than the second set voltage; if the current voltage of the electric pump is less than or equal to the second set voltage, the electric pump is in a non-dry-running state; and when the electric pump is determined to be in a non-dry rotation state, controlling the rotation speed of the electric pump to be kept unchanged.

5. A control method according to claim 1 or 2, characterized by defining a fourth limiting current, which is greater than the second limiting current and less than the third limiting current, defining a set of current values between the second limiting current and the fourth limiting current as a first subinterval; the control module judges the relation between the current of the electric pump and the first subinterval, judges the relation between the current rotating speed of the electric pump and a third set rotating speed if the current of the electric pump is in the first subinterval, and is in a dry-running state if the current rotating speed of the electric pump is less than or equal to the third set rotating speed; and when the electric pump is in a dry-running state, controlling the electric pump to stop running, or controlling the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed, wherein the limited rotating speed is greater than the minimum rotating speed and less than the maximum rotating speed.

6. The control system according to claim 5, wherein a relationship between a current rotation speed of the electric pump and the third set rotation speed is determined, a relationship between a current voltage of the electric pump and a third set voltage is determined if the current rotation speed of the electric pump is greater than the third set rotation speed, and the electric pump is in a dry running state if the current voltage of the electric pump is less than the third set voltage; when the electric pump is in a dry-running state, controlling the electric pump to stop running, or controlling the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed, wherein the limited rotating speed is greater than a minimum rotating speed and less than a maximum rotating speed; if the current voltage of the electric pump is greater than or equal to the third set voltage, the electric pump is in a non-dry-running state; and when the electric pump is determined to be in a non-dry rotation state, controlling the rotation speed of the electric pump to be kept unchanged.

7. The control system according to claim 5 or 6, characterized in that a set of current values between the fourth limiting current and the third limiting current is defined as a second subinterval; judging the relation between the current of the electric pump and the second subinterval, if the current of the electric pump is in the second subinterval, judging the relation between the current rotating speed of the electric pump and a fourth set rotating speed, and if the current rotating speed of the electric pump is less than the fourth set rotating speed, the electric pump is in a dry-running state; when the electric pump is in a dry-running state, controlling the electric pump to stop running, or controlling the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed, wherein the limited rotating speed is greater than a minimum rotating speed and less than a maximum rotating speed; if the current rotating speed of the electric pump is greater than or equal to the fourth set rotating speed, judging the relation between the current voltage of the electric pump and the fourth set voltage, and if the current voltage of the electric pump is greater than the fourth set voltage, enabling the electric pump to be in a dry-running state; if the current voltage of the electric pump is less than or equal to the fourth set voltage, the electric pump is in a non-dry-running state; and when the electric pump is determined to be in a non-dry rotation state, controlling the rotation speed of the electric pump to be kept unchanged.

8. A control system capable of controlling an electric pump, the control system comprising a control module in signal connection with a detection module, the control module capable of controlling the operation and/or stop of the electric pump; the detection module comprises a current detection unit and a rotating speed detection unit, and the control module can obtain the current of the electric pump through the current detection unit; the control module can obtain the current rotating speed of the electric pump through the rotating speed detection unit; the control method of the control system according to any one of claims 1 to 7.

9. The control system of claim 8, wherein the control module determines a current of the electric pump versus the first interval; the control module judges the relation between the current rotating speed of the electric pump and a first set rotating speed; the control module controls the electric pump to stop running or controls the rotating speed of the electric pump to be less than or equal to a limited rotating speed; the control module controls the rotating speed of the electric pump to be kept unchanged; the detection module further comprises a voltage detection unit, and the control module can obtain the current voltage of the electric pump through the voltage detection unit.

10. An electric pump comprising an electric motor, a pump shaft, an impeller, and a circuit board, the electric motor comprising a rotor component and a stator component, the rotor component being in driving connection with the impeller via the pump shaft, the circuit board incorporating a control system, the control system being the control system of claim 8 or 9; the current of the electric pump is the current passing through the stator part, the current rotating speed of the electric pump is the rotating speed of the rotor part of the motor, and the current voltage of the electric pump is the input voltage of the electric pump.

Technical Field

The invention relates to the technical field of motor control, in particular to an electric pump and control thereof.

Background

When the electric pump works, if the electric pump is in a dry-running state, abrasion of a pump shaft, an impeller and the like may be caused, adverse effects such as heat dissipation of the electric pump may be caused, and the service life of the electric pump may be reduced.

Disclosure of Invention

The invention aims to provide a control method, a control system and an electric pump, which are beneficial to prolonging the service life of the electric pump.

A control method capable of controlling an electric pump, defining a first limit current and a second limit current, the first limit current, the second limit current increasing with an increase in a rated voltage of the electric pump; wherein the first limiting current is less than the second limiting current; defining a set of current values between the first limiting current and the second limiting current as a first interval; judging the relation between the current of the electric pump and the first interval, if the current of the electric pump is in the first interval, judging the relation between the current rotating speed of the electric pump and a first set rotating speed, and if the current rotating speed of the electric pump is greater than or equal to the first set rotating speed, the electric pump is in a dry rotation state; and when the electric pump is in a dry-running state, controlling the electric pump to stop running, or controlling the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed, wherein the limited rotating speed is greater than the minimum rotating speed and less than the maximum rotating speed.

A control system capable of controlling an electric pump, the control system comprising a control module in signal connection with a detection module, the control module capable of controlling the operation and/or stop of the electric pump; the detection module comprises a current detection unit and a rotating speed detection unit, and the control module can obtain the current of the electric pump through the current detection unit; the control module can obtain the current rotating speed of the electric pump through the rotating speed detection unit; the control method of the control system is the control method described above.

An electric pump comprises a motor, a pump shaft, an impeller and a circuit board, wherein the motor comprises a rotor part and a stator part, the rotor part is in transmission connection with the impeller through the pump shaft, the circuit board is integrated with a control system, and the control system is the control system; the current of the electric pump is the current passing through the stator part, the current rotating speed of the electric pump is the rotating speed of the rotor part of the motor, and the current voltage of the electric pump is the input voltage of the electric pump.

The invention discloses a control method, a control system and an electric pump, wherein the control system can control the electric pump, sets a first limit current smaller than a second limit current, defines a set of current values between the first limit current and the second limit current as a first interval, further judges according to the relation between the current rotating speed of the electric pump and the first set rotating speed when the current of the electric pump is in the first interval, and judges that the electric pump is in a dry running state when the current rotating speed of the electric pump is greater than or equal to the first set rotating speed; therefore, when the electric pump is judged to be in the dry running state, not only the current factor but also the rotating speed of the electric pump are further considered, so that the electric pump is favorably judged to be in the dry running state.

Drawings

FIG. 1 is a schematic block diagram of the connection of an electric pump control system according to one aspect of the present invention;

FIG. 2 is a schematic block diagram of the connection of an electric pump control system according to another embodiment of the present invention;

FIG. 3 is a schematic diagram of the relationship between the dry running state and the first set rotating speed of the electric pump when the current of the electric pump is in the first interval;

FIG. 4 is a schematic diagram showing the relationship between the dry running state of the electric pump and the first set rotational speed and the first set voltage when the current of the electric pump is in the first interval;

FIG. 5 is a schematic diagram of the relationship between the dry running state and the second set rotating speed of the electric pump when the current of the electric pump is in the second interval;

FIG. 6 is a schematic diagram showing the relationship between the dry running state of the electric pump and the second set rotating speed and the second set voltage when the current of the electric pump is in the second interval;

FIG. 7 is a schematic diagram of the relationship between the dry-running state and the third set rotational speed of the electric pump when the current of the electric pump is in the first sub-interval;

FIG. 8 is a schematic diagram of the relationship between the dry-running state of the electric pump and the third set rotating speed and the third set voltage when the current of the electric pump is in the first sub-interval;

FIG. 9 is a schematic diagram of the relationship between the dry running state and the fourth set rotating speed of the electric pump when the current of the electric pump is in the second subinterval;

FIG. 10 is a schematic diagram of the relationship between the dry running state of the electric pump and the fourth set rotating speed and the fourth set voltage when the current of the electric pump is in the second subinterval;

FIG. 11 is a control flow diagram of an embodiment of the present invention;

fig. 12 is a control flow diagram when the present current of the electric pump is in the first interval;

fig. 13 is a schematic diagram of a first control flow when the present current of the electric pump is in a second interval;

FIG. 14 is a schematic control flow chart of the second embodiment when the present current of the electric pump is in the first subinterval;

fig. 15 is a control flow diagram when the present current of the electric pump is in the second subinterval in the second embodiment.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The invention is further described with reference to the following figures and detailed description:

an embodiment of the present invention provides a control system for controlling an electric pump, which can be applied to the field of automobiles, and a control method thereof. Referring to fig. 1, the control system includes a control module 10 capable of controlling the operation and/or stop of the electric pump 100 and a detection module 30, the control module 10 being in signal connection with the detection module 30. The electric pump 100 includes a motor 40, a pump shaft, and an impeller 50, the motor 40 is in transmission connection with the impeller 50, the motor 40 can drive the impeller 50 to rotate, specifically, the motor includes a stator part and a rotor part, and the rotor part is in transmission connection with the impeller through the pump shaft. In one embodiment, the control system further includes a driving module 20, such that the control module 10 outputs a control signal to the driving module 20, the driving module 20 generates a corresponding driving signal, the driving module 20 is electrically connected to the stator component, the motor 40 drives the impeller to operate according to the driving signal, specifically, an excitation magnetic field is generated around the stator component, the rotor component rotates in the excitation magnetic field, and the rotor component can drive the impeller to rotate through the pump shaft, so as to control the flow of the fluid in the electric pump.

The detection module 30 is capable of detecting the current of the electric pump and the current rotation speed of the electric pump; specifically, the detection module 30 includes a current detection unit and a rotation speed detection unit, the current detection unit can obtain the current of the motor stator component of the electric pump and form a current detection signal, and the control module 10 can analyze the current detection signal to obtain the current of the electric pump. The rotating speed detection unit can acquire the rotating speed of the electric pump and form a rotating speed detection signal, and the control module can analyze the rotating speed detection signal to obtain the current rotating speed of the electric pump, wherein the rotating speed detection unit can adopt a Hall sensor, and the control module can also adopt other modes to obtain the current rotating speed of the electric pump, such as a photoelectric sensor and the like.

The detection module further comprises a voltage detection unit, and the control module can obtain the current voltage of the electric pump through the voltage detection unit. Specifically, the voltage detection unit can acquire the input voltage of the electric pump and form a voltage detection signal, more specifically, the voltage detection unit can be a second sampling resistor, the control module acquires the voltage detection signal through the second sampling resistor, and the current voltage of the electric pump is obtained through calculation. The control module 10 includes a storage unit (not shown) and a processing unit (not shown) in signal connection with the storage unit, the processing unit is used for information processing, and the storage unit is used for storing relevant parameters. It is understood that the control system may be provided separately from the electric pump, or the control system may be integrated with a circuit board of the electric pump, as shown in fig. 2. The control signal output by the control module may be a pulse width modulation signal.

In particular, for easier understanding of the description of the specific operation steps, the meanings of "first interval", "second interval", "first subinterval", "second subinterval", "first limited current", "second limited current", "fourth limited current", "first set rotation speed", "second set rotation speed", "third set rotation speed", "fourth set rotation speed", "first set voltage", "second set voltage", "third set voltage", "fourth set voltage", and "dry running state", which will be mentioned later, are explained in advance herein.

Referring to FIG. 3, a first limiting current I is defined₁A second limiting current I₂And a third limiting current I₃Wherein the first limiting current I₁A second limiting current I₂And a third limiting current I₃The first limiting current I increases as the rated voltage of the electric pump increases₁Less than a third limit current I₃Second limiting current I₂Greater than a first limit current I₁And is less than the third limit current I₃(ii) a Defining a first limiting current I₁And a second limiting current I₂The set of current values in between is a first interval; defining a second limiting current I₂And a third limiting current I₃The set of current values in between is the second interval.

In another embodiment of the present invention, referring to FIG. 7, a fourth limiting current I is defined₄Fourth limiting the current I₄The fourth limiting current I increases as the rated voltage of the electric pump increases₄Greater than the second limit current I₂And is less than the third limit current I₃The second interval comprises a first sub-interval and a second sub-interval, and defines a second limiting current I₂And a fourth limiting current I₄The set of currents in between is a first subinterval; defining a fourth limiting current I₄And a third limiting current I₃The set of current values in between is the second subinterval.

In the embodiment of the present technical solution, the rated voltage of the electric pump is 13V, the first limiting current is 0.6A, the second limiting current is 0.7A, the third limiting current is 1.4A, the fourth limiting current is 1.2A, and several different forms of the rated voltage of the electric pump, the first limiting current, the second limiting current, the third limiting current, and the fourth limiting current are shown in the following table:

the electric pump has a maximum rotating speed and a minimum rotating speed, wherein the maximum rotating speed is the highest rotating speed allowed by the electric pump to run for a short time to ensure the service life of the electric pump, the minimum rotating speed is the lowest rotating speed allowed by the electric pump to work reliably or the running efficiency, when the electric pump works at the maximum rotating speed for a long time, the service life of the electric pump is shortened, and when the electric pump works at the minimum rotating speed for a long time, the efficiency of the electric pump is lower; in order to take the efficiency and the service life of the electric pump into consideration, a limited rotating speed is defined, and the limited rotating speed is greater than the minimum rotating speed and less than the maximum rotating speed; defining a first set rotating speed, a second set rotating speed, a third set rotating speed and a fourth set rotating speed, wherein the first set rotating speed, the second set rotating speed, the third set rotating speed and the fourth set rotating speed are all larger than the minimum rotating speed and smaller than the maximum rotating speed, the first set rotating speed, the second set rotating speed, the third set rotating speed and the fourth set rotating speed can be equal, and the first set rotating speed, the second set rotating speed, the third set rotating speed and the fourth set rotating speed can also be unequal; further, in the present technical solution, the first set rotation speed, the second set rotation speed, the third set rotation speed, and the fourth set rotation speed are equal to half of the sum of the maximum rotation speed and the minimum rotation speed, that is, (the maximum rotation speed + the minimum rotation speed)/2. The first setting voltage, the second setting voltage, the third setting voltage and the fourth setting voltage may be rated voltages when the electric pump operates, or may be set according to actual requirements, wherein the first setting voltage, the second setting voltage, the third setting voltage and the fourth setting voltage may be equal, and the first setting voltage, the second setting voltage, the third setting voltage and the fourth setting voltage may not be equal. The "dry running state" indicates a state in which the fluid in the electric pump is insufficient, and when the electric pump is operated, the fluid content in the electric pump is less than or equal to a set multiple of the maximum fluid capacity in the electric pump, and the set multiple is related to the operation mode of the electric pump and can be set according to the actual operation mode of the electric pump.

An aspect of the present invention also provides a control method for an electric pump, where in a first embodiment of the control method for an electric pump according to the present invention, referring to fig. 3 to 6 and 11 to 13, the control method includes: the control system is powered on, the control module obtains the current of the electric pump, the control module judges the relation between the current of the electric pump and a first interval, if the current of the electric pump is larger than a first limit current and smaller than a second limit current, the current of the electric pump is in the first interval, the control module judges the relation between the current rotating speed of the electric pump and a first set rotating speed, if the current rotating speed of the electric pump is larger than or equal to the first set rotating speed, the control module judges that the electric pump is in a dry rotating state, the control module stops outputting a control signal to control the electric pump to stop operating, or the control module controls the rotating speed of the electric pump to be smaller than or equal to a preset limit rotating speed. Because when the present electric current of electric pump was in first interval, control module further judged the running state of electric pump according to the relation of the present rotational speed of electric pump and first settlement rotational speed, like this, when judging whether electric pump is in the dry-running state, not only considered the factor of electric current, still further considered the rotational speed of electric pump, consequently, can be favorable to judging whether electric pump is in the dry-running state, improve the life of pump shaft relatively to be favorable to improving the life of electric pump.

The control module judges the relation between the current rotating speed of the electric pump and a first set rotating speed, if the current rotating speed of the electric pump is less than the first set rotating speed, the control module judges the relation between the current voltage of the electric pump and a first set voltage, if the current voltage of the electric pump is less than or equal to the first set voltage, the control module judges that the electric pump is in a dry-running state, the control module stops outputting a control signal to control the electric pump to stop running, or the control module outputs a control signal to control the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed; if the current voltage of the electric pump is larger than the first set voltage, the control module judges that the electric pump is in a non-dry rotation state, and the control module outputs a control signal to control the rotating speed of the electric pump to keep unchanged. When the current of the electric pump is in the first interval, the judgment result of the control module may misjudge the operation state of the electric pump, the control module further judges the operation state of the electric pump according to the relation between the current rotating speed of the electric pump and the first set rotating speed, and the control module further judges the operation state of the electric pump according to the relation between the current rotating speed of the electric pump and the first set voltage.

In the control system, the control module may perform the following settings: the current of the electric pump is smaller than or equal to the first limiting current, the electric pump is set to be in a dry-running state, the current of the electric pump is larger than the third limiting current, the electric pump is set to be in a non-dry-running state, and the control module can call the set relation when judging the running state of the electric pump. In the control system, the control module may perform the following determination: the control module judges whether the current of the electric pump is smaller than or equal to a first limit current, if the current of the electric pump is smaller than or equal to the first limit current, the control module judges that the electric pump is in a dry-running state, the control module stops outputting a control signal to control the electric pump to stop running, or the control module outputs a control signal to control the rotating speed of the electric pump to be smaller than or equal to a preset limit rotating speed; the control module judges whether the current of the electric pump is larger than a third limiting current, if so, the control module judges that the electric pump is in a non-dry-running state, and the control module outputs a control signal to control the rotating speed of the electric pump to keep unchanged.

The control module judges the relation between the current of the electric pump and a second interval, if the current of the electric pump is in the second interval, the control module judges the relation between the current rotating speed of the electric pump and a second set rotating speed, if the current rotating speed of the electric pump is smaller than the second set rotating speed, the control module judges that the electric pump is in a dry rotating state, the control module stops outputting a control signal to control the electric pump to stop running, or the control module outputs the control signal to control the rotating speed of the electric pump to be smaller than or equal to a preset limited rotating speed. Because when the current of electric pump is in the second interval, control module further judges the running state of electric pump according to the relation of the current rotational speed of electric pump and the second settlement rotational speed, like this, when judging whether electric pump is in the dry running state, not only consider the factor of electric current, still further consider the influence of the rotational speed of electric pump to the running state of electric pump, consequently, can be favorable to judging whether electric pump is in the dry running state, improve the life of pump shaft relatively, in order to be favorable to improving the life of electric pump.

The control module judges the relation between the current rotating speed of the electric pump and a second set rotating speed, if the current rotating speed of the electric pump is greater than or equal to the second set rotating speed, the control module judges the relation between the current voltage of the electric pump and a second set voltage, if the current voltage of the electric pump is greater than the second set voltage, the control module judges that the electric pump is in a dry-running state, the control module stops outputting a control signal to control the electric pump to stop running, or the control module outputs a control signal to control the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed; if the current voltage of the electric pump is smaller than or equal to the second set voltage, the control module judges that the electric pump is in a non-dry-running state, and the control module keeps outputting a control signal to control the rotating speed of the electric pump to keep unchanged. When the current of the electric pump is in the second interval, the judgment result of the control module can misjudge the running state of the electric pump, the control module further judges the running state of the electric pump according to the relation between the current rotating speed of the electric pump and the second set rotating speed, and the control module further judges the running state of the electric pump according to the relation between the current rotating speed of the electric pump and the second set voltage.

Before the control module determines the operating state of the electric pump, the control method further includes: the control module acquires a first interval and a second interval; the first interval is a set of current values between the first limiting current and the second limiting current, the second interval is a set of current values between the second limiting current and the third limiting current, and when the current of the electric pump is in the first interval or the second interval, the operation state of the electric pump cannot be accurately judged only according to the current of the electric pump, and the first interval and the second interval are divided so as to be convenient for subsequent judgment of the operation state of the electric pump.

In the first embodiment, the control module determines the relationship between the current of the electric pump and the first interval, and the control module determines the relationship between the current of the electric pump and the second interval, and the determination sequence of the two is not limited, specifically, the control module may first determine the relationship between the current of the electric pump and the first interval, and then determine the relationship between the current of the electric pump and the second interval; the control module may first determine a relationship between a current of the electric pump and the second interval, and then determine a relationship between the current of the electric pump and the second interval.

The invention provides a control method of a control system, wherein the flow schematic diagram of a second implementation mode of the control method is shown in fig. 3, fig. 4, fig. 7 to fig. 11, and fig. 13 to fig. 15, and the main difference from the first implementation mode is that: the control method further comprises the following steps: if the current of the electronic pump is in the second interval, the control module judges the relationship between the current of the electric pump and the first subinterval, if the current of the electric pump is in the first subinterval, the control module judges the relationship between the current rotating speed of the electric pump and the third set rotating speed, if the current rotating speed of the electric pump is less than or equal to the third set rotating speed, the control module judges that the electric pump is in a dry-running state, the control module stops outputting a control signal to control the electric pump to stop running, or the control module outputs a control signal to control the rotating speed of the electric pump to be less than or equal to the preset limited rotating speed. Because when the current of electric pump is in first subinterval, control module further judges the running state of electric pump according to the relation of the current rotational speed of electric pump and the third settlement rotational speed, like this, when judging whether electric pump is in the dry run state, not only consider the factor of electric current, still further consider the influence of the rotational speed of electric pump to the running state of electric pump, consequently can be favorable to judging whether electric pump is in the dry run state, improve the life of pump shaft relatively, in order to be favorable to improving the life of electric pump.

If the current of the electronic water pump is in a second interval, the control module judges the relationship between the current rotating speed of the electric pump and a third set rotating speed, if the current rotating speed of the electric pump is greater than the third set rotating speed, the control module judges the relationship between the current voltage of the electric pump and a third set voltage, if the current voltage of the electric pump is less than the third set voltage, the control module judges that the electric pump is in a dry-running state, the control module stops outputting a control signal to control the electric pump to stop running, or the control module outputs a control signal to control the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed; if the control module judges that the current voltage of the electric pump is greater than or equal to the third set voltage, the control module judges that the electric pump is in a non-dry rotation state, and the control module outputs a control signal to control the rotating speed of the electric pump to be kept unchanged. When the current of the electric pump is in the second subinterval, the judgment result of the control module can misjudge the running state of the electric pump, the control module further judges the running state of the electric pump according to the relation between the current rotating speed of the electric pump and the third set rotating speed, and the control module further judges the running state of the electric pump according to the relation between the current rotating speed of the electric pump and the third set voltage.

If the current of the electric pump is in the second interval, the control module judges the relationship between the current of the electric pump and the second subinterval, if the current of the electric pump is in the second subinterval, the control module judges the relationship between the current rotating speed of the electric pump and the fourth set rotating speed, if the current rotating speed of the electric pump is less than the fourth set rotating speed, the control module judges that the electric pump is in a dry-running state, the control module stops outputting the control signal to control the electric pump to stop running, or the control module outputs the control signal to control the rotating speed of the electric pump to be less than or equal to the preset limited rotating speed. If the current rotating speed of the electric pump is greater than or equal to a fourth set rotating speed, the control module judges the relationship between the current voltage of the electric pump and the fourth set voltage, if the current voltage of the electric pump is greater than the fourth set voltage, the control module judges that the electric pump is in a dry-running state, the control module stops outputting a control signal to control the electric pump to stop running, or the control module outputs a control signal to control the rotating speed of the electric pump to be less than or equal to a preset limited rotating speed; if the current voltage of the electric pump is less than or equal to the fourth set voltage, the control module judges that the electric pump is in a non-dry-running state, and the control module outputs a control signal to enable the rotating speed of the electric pump to be kept unchanged. In the second embodiment, the effects of the first embodiment can be achieved, the second section is further divided into the first subinterval and the second subinterval, and the relationship between the electric current of the electric pump and the first subinterval and the second subinterval is determined, respectively.

In a second embodiment, the control module judges the relationship between the current of the electric pump and the first subinterval, the control module judges the relationship between the current of the electric pump and the second subinterval, and the judging order of the two is not limited; specifically, if the current of the electric pump is in the second interval, the control module may first determine a relationship between the current of the electric pump and the first subinterval, and then determine a relationship between the current of the electric pump and the second subinterval; the control module may also first determine a relationship between a present current of the electric pump and the second subinterval, and then determine a relationship between the current of the electric pump and the second subinterval.

It should be noted that: although the present invention has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.