Electrically driven mobile compressor or pump and method for controlling the maximum current that is taken from a power supply

Abstract

Electrically driven mobile compressor or pump, comprising at least one compressor element or pump element for supplying a pressurised fluid to a network of consumers of such pressurised fluid; an electric drive motor with a variable speed control coupled to the compressor element or pump element and a controller for the variable speed control of the electric drive motor as a function of the flow rate of compressed gas and/or pressure demanded by the network, and a connection for connection of the compressor or pump to an electricity supply source, and the controller is provided with an algorithm with which the electric current drawn from the supply source can be limited to a set or adjustable maximum value by controlling the speed.

Claims

1. An electrically driven mobile compressor or pump comprising at least one compressor element or pump element for supplying a pressurised fluid to a network of consumers of such pressurised fluid; an electric drive motor with a variable speed control coupled to the compressor element or pump element, and an electric or electronic controller comprising a first controller configured to control the speed or the pressure of the compressor or pump, respectively as a function of a set desired pressure or a set desired flow rate, of the pressurised fluid demanded by the network, and a second controller configured for the variable speed control of the electric drive motor as a function of a desired speed that is determined by the first controller, and a connection for connecting the compressor or pump to an electricity supply source, wherein the controller is provided with an algorithm with which the electric current drawn from the supply source can be limited to a set or adjustable maximum value by limiting the controlled speed at a desired pressure, or limiting the controlled pressure at a desired flow rate, to a maximum value, the case of a set desired pressure or desired flow rate respectively, and whereby the electric or electronic control that limits the speed or the pressure in order not to exceed a maximum drawn current, is a control with a fixed set value of the maximum speed or of the maximum pressure, whereby this value is calculated or determined as a function of the characteristics of the compressor or pump and based on the set maximum current to be drawn together with the set desired pressure, or based on the set maximum current to be drawn together with the set desired flow rate respectively, wherein when a desired pressure has been set, the pressure is maintained and the speed is controlled to maintain the pressure for as long as the current drawn is below the set maximum current, and wherein, as soon as the drawn current reaches the set maximum current, the maximum speed is limited; and wherein when a desired flow rate has been set, the speed corresponding to the set flow rate is maintained and the pressure is adjusted to maintain the flow rate or speed for as long as the current drawn is below the set maximum current, and wherein, as soon as the drawn current reaches the set maximum current, the maximum pressure is limited.

2. The electrically driven mobile compressor or pump according to claim 1, wherein means are provided to be able to determine or measure the drawn current, continuously or at intervals, whereby the algorithm is such that, if the measured drawn current is less than the set maximum current, the control of the speed by the aforementioned controller is left undisturbed, but whereby, when the measured drawn current is equal to or greater than the set maximum current, the controller will keep the speed constant or decrease it until the measured drawn current is again less than the set maximum current.

3. The electrically driven mobile compressor or pump according to claim 1, wherein the compressor or pump is provided with a first control that enables a maximum permissible value of the current to be set.

4. The electrically driven mobile compressor or pump according to claim 3, wherein the first control can be set to a series of preprogrammed selection values.

5. The electrically driven mobile compressor or pump according to claim 4, wherein the preprogrammed selection values are shown on a selection scale, which itself is adjustable by means of a second control as a function of the current protection of electricity supply sources that are common in a certain region or similar.

6. The electrically driven mobile compressor or pump according to claim 4, wherein the electrically driven mobile compressor or pump is provided with means to determine the voltage and/or frequency of the electricity supply source and to show preprogrammed selection values of current protection on a selection scale that are common in a certain region or similar, in combination with the measured voltage and/or frequency.

7. The electrically driven mobile compressor or pump according to claim 4, wherein the electrically driven mobile compressor or pump is provided with means to determine the GPS coordinates of the compressor or pump and to show preprogrammed selection values of current protection on a selection scale that are common in the region where the compressor or pump is located according to the determined GPS coordinates.

8. The electrically driven mobile compressor or pump according to claim 3, wherein the aforementioned first control and/or a second control is or are protected by a key, a password or similar.

9. The electrically driven mobile compressor or pump according to claim 2, wherein it is provided with one or more electrical connections that are intended for any electricity supply of external electrical consumers, whereby the current of one or more electrical connections is tapped off at a location downstream from the means for determining or measuring the drawn current, so that the current that is measured with the means is the combined current drawn from the supply source by the compressor or pump and by the electrical consumers connected to the electrical connections concerned.

10. The electrically driven mobile compressor or pump according to claim 2, wherein the aforementioned electricity supply source is taken from a power point of an electrical grid, whereby this power point is electrically protected by a fuse of the electricity supply source or of an electrical grid, whereby the safety current of the fuse determines the value of the maximum current to be set on the electrically driven mobile compressor or pump.

11. The electrically driven mobile compressor or pump according to claim 1, wherein it is provided with an audio or visual signal that gives an alarm when the maximum current is reached or is almost reached, or which indicates how much of the available current or power is consumed or is still available.

12. The electrically driven mobile compressor or pump according to claim 1, wherein it comprises two or more connections for connection to two or more different electricity supply sources that can supply the compressor or pump with current in parallel simultaneously.

13. The electrically driven mobile compressor or pump according to claim 12, wherein for each connection for connection to an electricity supply source, it is provided with means to determine the drawn current, continuously or at intervals, and to set a maximum permissible value of the current per connection.

14. The electrically driven mobile compressor or pump according to claim 13, wherein the controller is provided with an algorithm with which the drawn electric current per connection can be limited to the set maximum permissible value for this connection, by distributing the total drawn electric current over the connected electrical connections and limiting the total drawn electric current to the sum of the set maximum permissible current values of all connections to which electricity supply sources are connected by controlling the speed.

15. The electrically driven mobile compressor or pump according to claim 14, wherein the compressor or pump is provided with a control that can be set so that the total electric current is drawn proportionally or according to an adjustable priority per connection.

16. The electrically driven mobile compressor or pump according to claim 12, wherein at least a first connection is provided for connection to an electrical grid and at least a second connection is provided for connection to a battery pack with one or more batteries to increase the available electric power with respect to the available power of the first connection.

17. The electrically driven mobile compressor or pump according to claim 16, wherein the electrically driven mobile compressor or pump is provided with means for charging the battery pack.

18. The electrically driven mobile compressor or pump according to claim 1, wherein the compressor element or pump element is a volumetric compressor element or pump element.

19. The electrically driven mobile compressor or pump according to claim 18, wherein the compressor element or pump element is a rotary compressor element or pump element.

20. A method for controlling a maximum electric current that can be drawn by a mobile compressor or pump from an electricity supply source, whereby the compressor or pump comprises a compressor element or pump element for supplying a pressurised fluid to a network of consumers and whereby the compressor element or pump element is coupled to an electric drive motor with a variable speed control, wherein the method comprises the following steps: connecting the compressor or pump to an electricity supply source; determining the maximum electric current that is desired or which is available from the supply source and setting the maximum electric current thus determined as the maximum electric current that can be drawn by the mobile compressor or pump; controlling the speed of the drive motor, or the pressure of the pressurised fluid, respectively as a function of a set desired pressure, or a set desired flow rate; and limiting the controlled speed at a desired pressure, or limiting the controlled pressure at a desired flow rate, to a maximum value in order to limit the drawn current to the aforementioned maximum current; wherein for the compressor or pump concerned, the prior calculation or determination of a fixed set value for the maximum value of the speed as a function of the characteristics of the compressor or pump and based on the set maximum current to be drawn together with the set desired pressure, or of a fixed set value for the pressure as a function of the set maximum current to be drawn together with the set desired flow rate respectively, to which the speed, or the pressure respectively, must be limited in order to limit the drawn current to the maximum current, or; the limitation of the speed, or the pressure, to the aforementioned calculated or determined maximum value, and wherein when a desired pressure has been set, the pressure is maintained and the speed is controlled to maintain the pressure for as long as the current drawn is below the set maximum current, and wherein, as soon as the drawn current reaches the set maximum current, the maximum speed is limited; and wherein when a desired flow rate has been set, the speed corresponding to the set flow rate is maintained and the pressure is adjusted to maintain the flow rate or speed for as long as the current drawn is below the set maximum current, and wherein, as soon as the drawn current reaches the set maximum current, the maximum pressure is limited.

21. The method according to claim 20, wherein the method further comprises the following steps: the continuous or periodic measuring or determining of the electric current drawn from the supply source; comparing the measured drawn current to the maximum current; leaving the aforementioned control of the speed at a desired pressure, or the pressure at a desired flow rate, undisturbed when the measured current is less than the set maximum current; and limiting the electric current drawn from the supply source to the maximum current by limiting the maximum value of speed in the case of a desired pressure, or by limiting the maximum value of the pressure in the case of a desired flow rate.

22. The method according to claim 20, wherein the supply source is provided with a fuse with a set safety current and the desired or selected maximum current is at most equal to the safety current of the fuse.

23. The method according to claim 20, wherein the compressor or pump is provided with one or more electrical connections that are intended for any electricity supply of external electrical consumers, whereby the current of these electrical connections together with the current of the drive motor is drawn from the supply source and whereby the method comprises the step of measuring the combined current drawn from the supply source and the step of limiting the combined electric current drawn from the supply source to the maximum current by controlling the speed.

24. The method according to claim 20, wherein it further comprises the step of generating an audio or visual signal that gives an alarm when the maximum current is reached or almost reached, or which indicates how much of the available current or power is consumed or is still available.

25. The method according to claim 20, wherein it further comprises connecting the compressor or pump to two or more different electricity supply sources that can supply the compressor or pump with current in parallel simultaneously and further comprises the following steps: for each supply source, determining of the maximum electric current that is desired or which is available from the supply source; for each electricity supply source, determining of the current drawn from the supply source concerned, continuously or at intervals; and for each supply source, limiting of the drawn current to the maximum current for the supply source concerned by distributing the total drawn electric current over the supply sources and limiting the total drawn electric current to the sum of the set maximum permissible current values of all connected supply sources by controlling the speed at a desired pressure or the pressure at a desired flow rate.

26. The method according to claim 25, wherein the total drawn electric current is distributed over the connected supply sources proportionally, or according to a chosen priority per connection.

27. The method according to claim 20, wherein it makes use of a compressor or pump comprising at least one compressor element or pump element for supplying a pressurised fluid to a network of consumers of such pressurised fluid; an electric drive motor with a variable speed control coupled to the compressor element or pump element, and an electric or electronic controller comprising a first controller configured to control the speed or the pressure of the compressor or pump, respectively as a function of a set desired pressure or a set desired flow rate, of the pressurised fluid demanded by the network, and a second controller configured for the variable speed control of the electric drive motor as a function of a desired speed that is determined by the first controller, and a connection for connecting the compressor or pump to an electricity supply source, wherein the controller is provided with an algorithm with which the electric current drawn from the supply source can be limited to a set or adjustable maximum value by limiting the desired set speed, or the desired set pressure, to a maximum value and whereby the electric or electronic control that limits the speed or the pressure in order not to exceed a maximum drawn current, is a control with a fixed set value of the maximum speed or of the maximum pressure, whereby this value is calculated or determined as a function of the characteristics of the machine and based on the set maximum current to be drawn together with the set desired pressure, or based on the set maximum current to be drawn together with the set desired flow rate respectively.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) With the intention of better showing the characteristics of the invention a few embodiments and applications of a mobile electrically driven compressor according to the invention are described hereinafter, by way of an example without any limiting nature, with reference to the accompanying drawings, wherein:

(2) FIG. 1 schematically shows a compressor according to the invention;

(3) FIGS. 2 and 3 each show a possible variant embodiment of a compressor according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows a mobile compressor 1 according to the invention comprising at least one compressor element 2 for compressing and supplying gas to a network 3 of consumers 4 of compressed gas; an electric drive motor 5 coupled to the compressor element 2 with a variable speed n, whereby this electric drive motor 5 is provided with a connection 6 to be able to be connected to an electricity supply 7 via a controller 8.

(5) This controller 8 comprises: a first controller 8a of the compressor element 2 configured to control the speed n or the pressure p respectively of the compressor or pump as a function of a set desired pressure pset, or a set desired flow rate Qset, and, a second controller 8b configured for the variable speed control of the electric drive motor 5 as a function of a desired speed nset that is determined by the first controller 8a.

(6) A normal control of a compressor can for example consist of, as is known, maintaining a set pressure pset in the network 3, or maintaining a determined set flow rate Qset.

(7) In the case of a set pressure pset having to be maintained, if the demand from the network 3 for the supply of compressed gas becomes greater for example, the pressure p in the network 3 will fall and the controller 8a will respond to this by increasing the desired speed nset of the drive motor 5 in order for the compressor element 2 to supply a higher flow of compressed gas until the pressure is again equal to the set value pset.

(8) In the case of a set flow rate Qset having to be maintained, if the pressure on the network 3 increases, the controller 8b will keep the speed n constant for example and the controller 8b will decrease the pressure with the speed remaining the same.

(9) The compressor 1 of the example comprises means 9 to measure the electric current I drawn from the supply source 7 and to pass it on to the controller 8 as a suitable signal.

(10) In the example of FIG. 1 the compressor 1 is further provided with a control system, which in this case is integrated in the controller 8, whereby this control system is provided with an algorithm 10 with which electric current I drawn from the supply source can be limited to a maximum value Imax by limiting the desired set speed nset or the desired set pressure pset to a maximum value, in the case of a set desired pressure pset or desired flow rate Qset respectively.

(11) The maximum value Imax is adjustable by means of a first control 11 that is connected to the controller 8.

(12) The control 11 is constructed in the form of a first multiposition switch for example, that enables a maximum value Imax of the current I to be set to a preprogrammed selection value, for example to be selected from a series of preset selection values on a selection scale 12. In the example, in this way a setting of 16, 32 or 63 amperes can be chosen depending on what is desired or what is available from the supply source 7.

(13) In the case of FIG. 1, the selection scale 12 is itself also adjustable by means of a second control 13, for example in the form of a second multiposition switch, which for example enables the selection scale 12 to be adjusted to the current protections that are common in a certain region.

(14) For example, in Europe a grid voltage of 400 volts is common with standard current protections of 16, 32, 63 and 125 amperes, while in the United States a grid voltage of 480 volts is usual with protections of 20, 30 and 50 amperes.

(15) In the example of FIG. 1 the multiposition switch 13 can be set for example for use in Europe with a voltage of 400 volts and 16 amperes.

(16) It is clear that the multiposition switch 13 can also be omitted, whereby for example the selection scale 12 comprises all common current values of current protection in a number of regions, for example a selection scale 12 with selection values 16, 20, 30, 32, 50 and 63 amperes for use in Europe and the United States.

(17) It is also clear that there can be other possibilities for setting the maximum current strength, for example via a digital setting with a keyboard or similar.

(18) The aforementioned algorithm 10 can for example consist of measuring the drawn current I, continuously or at intervals, and comparing it to the set maximum current Imax and conducting the control such that if the measured drawn current is less than the set maximum current Imax, the normal control of the speed n or the pressure by the aforementioned controller 8a and/or controller 8b is left undisturbed, but whereby, when the measured drawn current I is equal to or greater than the set maximum current Imax, the controller 8 will keep the speed n or the pressure p constant or decrease it until the measured drawn current I is again less than the set maximum current Imax.

(19) When in a certain situation with a set desired pressure pset, for example, an extra consumer 4 is connected to the network 3, this will increase the demand for compressed gas. This will elicit a response from the controller 8 in a known way by increasing the speed n of the drive motor 5 of the compressor element 2. With the operating pressure in the network 3 remaining the same, this will lead to an increased current I drawn from the supply source 7.

(20) For as long as the measured drawn current I in this situation is less than Imax, the variable speed control will be left undisturbed and it can adjust the speed n undisturbed within certain boundaries upon an increase or decrease of the consumption of the network 3, but when the measured current I is equal to Imax, the algorithm 10 will ensure that the speed cannot increase further or will decrease when the current I is greater than or threatens to become greater than Imax.

(21) When in a certain situation with a set desired flow rate Qset, for example, the resistance of the network 3 changes, this will change the pressure, while the desired flow rate must remain constant. This will elicit a response from the controller 8 in a known way by adjusting the pressure p at a constant speed of the drive motor 5 of the compressor element 2. In the case of a pressure increase this will lead to an increased current I drawn from the supply source 7.

(22) If a desired flow rate Qset has been set, in a certain situation in which the pressure in the network 3 decreases while the desired flow rate must remain constant, this will elicit a response from the controller 8 in a known way, by increasing the pressure p with the speed remaining the same, as controlled by the controller 8b. With a constant flow rate to the network 3 this will lead to an increased current I drawn from the supply source 7.

(23) In this last case, as long as the measured drawn current I is less than Imax, the variable pressure control will be left undisturbed and it can adjust the pressure p to the pressure of the network 3 undisturbed within certain boundaries, but when the measured current I is equal to Imax the algorithm 10 will ensure that the pressure cannot increase further or will decrease when the current I is greater than or threatens to become greater than Imax.

(24) FIG. 2 shows a variant of a compressor 1 according to the invention, whereby the selection scale 12 for the maximum current to be set by the controller 8 itself is determined as a function of the voltage V of the electricity supply source 7 to which the compressor 1 is connected, and which can be measured in a known way using a voltmeter 14. Alternatively instead of the voltage, the frequency or a combination of both can also be measured.

(25) Furthermore this compressor 1 of FIG. 2 differs from the previous embodiment of FIG. 1 in the fact that it is provided with one or more electrical connections 15 that are tapped off downstream from the means 9, in this case downstream from the controller 8, and which are intended for the electricity supply of external electrical consumers 16. In this way the means 9 measure the current that is consumed by the drive motor 5 of the compressor element 2, the controller 8 and the external consumers 16 together.

(26) It is thus ensured that the combined drawn current can never go above the limit of the set maximum current Imax.

(27) In the example of FIGS. 1 and 2 the electricity supply 7 is taken from a power point 17 of an electrical grid, whereby this power point 17 is electrically protected by means of a fuse 18 or other protection of the electrical grid, the safety current of which determines the value of the maximum current Imax to be set for the electrically driven mobile compressor 1.

(28) In FIG. 3 two different supply sources 7 are used for the electricity supply of the compressor 1, respectively a first supply source 7a in the form of a first connection 6a to an electrical grid and a second supply source 7b in the form of a second connection 6b to a battery pack 19. The first connection 6a comprises a power point 17a and is protected with a fuse 18a, the second connection 6b comprises a power point 17b and is protected with a fuse 18b.

(29) Depending on the desired power and the situation, only the first supply source 7a or the second supply source 7b can be drawn on, and current can be drawn from both simultaneously in parallel, in which case an increased power is temporarily available if desired.

(30) In the embodiment of FIG. 3 there is also an audio or visual signal 20 that gives an alarm when the maximum current Imax is reached or almost reached, or which indicates how much of the available current or power is consumed or is still available.

(31) The present invention is by no means limited to the embodiments described as an example and shown in the drawings, but a mobile electrically driven compressor and method according to the invention can be realised in all kinds of forms and dimensions without departing from the scope of the invention.