Air compressor with an internal inverter enabling pressurized unload to stop

Abstract

An air compressor (101) having an electrical inverter (165) controlling an air compression element (122), with the electrical inverter (165) being internal to the air compressor (101) and housed in an electrical cubicle (123). During an unload and stop phase of the air compressor (101), pressure within a pressure vessel (121) is maintained at an elevated level, reducing the time and power required for the air compressor (101) to return to a fully loaded state.

Description

DescriptionTitle of Invention: AIR COMPRESSOR WITH AN INTERNAL INVERTER ENABLING PRESSURIZED UNLOAD TO STOP

[0001] FIELD OF THE DISCLOSURE

[0002] The disclosure is related to an air compressor having an internal inverter allowing a pressurized unload to stop.BACKGROUND

[0003] A rotary screw air compressor is a type of positive displacement gas compressor that uses two rotors to create pressure needed for air compression. The two rotors rotate in opposite directions to draw in air that is compressed as the space between the rotors and the rotor housing decreases. Each screw element has a fixed, built-in pressure ratio dependent on the length and pitch of the screw, and form of the discharge port. To attain maximum efficiency, the built-in pressure ratio must be adapted to the required working pressure. The order of operation of these compressors is determined by the pressure values, and the different scenarios that arise in the factory present varying compressor loads of operation, such as no-load, standby, ready to operate, and load settings. The varying compressed air requirements of a factory can be met by different types of compressors, such as a variable speed drive (VSD) or fixed speed drive compressor.

[0004] Traditional fixed speed compressors operate at fixed revolutions per minute (RPM) over time and supply a consistent frequency output to the motor. To adjust the airflow amount, a fixed-speed air compressor requires adjustment of the air inlet valve to let more or less air out. Traditional fixed speed compressors also switch between operation states: a) no-load; and b) load. During the no-load state, the air is recirculated within the compressor and no airflow is generated. Once the pressure in the compressor outlet reaches the unload pressure level, the motor goes to unload before going to stop. And when the compressed air is partially used, the pressure of the air storage tank decreases. After the pressure reaches the load pressure level, the motor is started again to drive the air compressor to work. After a certain amount of operating time the motor will start and stop frequently, and the motor will consume more electric energy during the starting and stopping process. To prevent current levels reaching elevated levels the internal compressor system is depressurized before a restart. Once the motor stops, the energy consumed by the frequent start and stop of the motor is increased. A disadvantage of traditional fixed speed compressors is that, even when the air demand is low, the motor always operates at the same fixed speed. Thus, this leadsto a less energy-efficient process and is a waste of energy due to the high amount of start / stops and high transient losses.

[0005] VSD compressors increase the speed of the motor as the need for air increases, thus supplying more flow. If the demand for air decreases, the motor will automatically slow down and only use the required energy to provide appropriate flow. During slow production days or breaks in workflow, VSD compressors are especially useful. This type of air compressor saves electricity and energy cost, compared to traditional fixed speed models. VSD compressors use stepless speed regulation characteristics of the motor for air pressure stability and thus address airflow needs according to the realtime demand for a factory. While VSD compressors are more energy-efficient for most applications, they are not necessary if the compressed air needs are constant, or even mostly constant with only occasional slight variations. For example, if the compressed air application is to run assembly-line machinery for 10-12 hours per day, investing in a variable speed compressor will require extra up-front investment costs.

[0006] Further adding to the inefficiency of fixed speed compressors is their inability to perform a star-delta startup when the pressure inside the pressure vessel is high. Doing so causes the current drawn to spike, leading to losses and potentially failure. There remains a need in the art for compressors having increased efficiency that can meet the needs of customers with varying applications.SUMMARY

[0007] Embodiments of the present disclosure are directed to an air compressor including a housing including a pressure vessel and an electrical cubicle and an air compression element within the housing and being configured to compress air for customer applications. The air compressor has an inverter in the electrical cubicle defining the speed of the air compression element, and the inverter operates the air compression element to compress the air into the pressure vessel in at least three phases: load, unload, and stop. During the load phase the inverter causes the air compression element to compress air into the pressure vessel, the pressure vessel having an outlet port from which the compressed air is selectively discharged towards the customers applications. During the unload phase the compressed air in the pressure vessel is maintained and the air is internally recirculated and / or blow-off towards an atmospheric pressure, and during the stop phase the air compression element is stopped and pressure within the pressure vessel is maintained. During a subsequent load phase, the inverter starts up without causing a spike in drawn current.

[0008] Further embodiments of the present disclosure are directed to a method for operating an air compressor having an internal inverter providing power to an air compression element. The method includes loading a pressure vessel of the air compressor withcompressed air from the air compression element to a first pressure level, discharging the compressed air from the pressure vessel, and unloading compressed air from the pressure vessel. Unloading comprises sealing the pressure vessel towards the customer application and reducing the air pressure within the pressure vessel by recirculating and / or blowing off air to reduce the air pressure within the pressure vessel to approach an atmospheric pressure. During the unload phase, the compressed air in the pressure vessel is internally recirculated and / or blown-off to reduce the air pressure in the pressure vessel to approach an atmospheric pressure at a second pressure level that is lower than the first pressure level and power consumption is operated at a diminished rate. Stopping the air compression element using the internal inverter with the air pressure maintained within the pressure vessel at a second pressure level lower than the first pressure level. Loading the pressure vessel of the air compressor with compressed air from the air compression element by raising the pressure from the second level to the first level and without dropping the air pressure below the second air pressure.

[0009] Still further embodiments of the present disclosure are directed to a method of operating an air compressor. The method includes executing a loading phase, an unloading phase, a stop phase, and a reloading phase. In the loading phase an internal inverter located within the housing of the air compressor powers an air compression element that pressurizes air into a pressure vessel and the pressure in the pressure vessel reaches a first pressure level. In the unloading phase the internal inverter slows the air compression element and the pressure within the pressure is reduced to a second pressure level lower than the first pressure level. During the unloading phase the pressure vessel is sealed towards the customer application and the pressure is reduced in the pressure vessel at the second pressure level. In the stop phase the motor is stopped and the pressure in the pressure vessel is maintained at the second pressure level. In the reloading phase the internal inverter powers the air compression element to elevate the pressure from the second pressure level to the first pressure level without permitting the pressure in the pressure vessel to fully dissipate.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Features, aspects, and advantages of the presently disclosed technology may be better understood concerning the following description, appended claims, and accompanying drawings. A person skilled in the relevant art will understand that the features shown in the drawings are purposes of illustration, and variations, including different or additional features and arrangements thereof, are possible.

[0011] Figure 1 illustrates example components of an example multi-modal compressor system.

[0012] Figure 2 is a graph of torque against speed for a motor of an air compressor according to embodiments of the prior art.

[0013] Figure 3 is a graph of torque against speed for a motor of an air compressor according to the present disclosure.

[0014] The drawings are to illustrate exemplary implementations and are not drawn to scale. It is understood that the inventions are not limited to the arrangements and instrumentalities shown in the drawings.

[0015] DEFINITIONS

[0016] For ease of understanding the disclosed embodiments of the disclosed method and system elements, a description of a few terms is necessary.

[0017] The term ‘compressor’ or ‘compressor device’ refers to a machine that draws low- pressure gas from auxiliary storage as raw input and then outputs high-pressure gas, either for storage or to feed other processes. The terms ‘compressor’ and ‘compressor device’ are not intended to be limiting in scope and may refer to positive displacement compressors and / or dynamic compressors (turbocompressors) and / or individual components of compressors.

[0018] The term ‘computer storage media’ refers to physical storage media that store computer-executable instructions and / or data structures. Storage media, such as a digital data carrier, includes computer hardware, such as random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), solid state drives (SSDs), flash memory, phase-change memory (PCM), optical disk storage, magnetic disk storage, and the like.

[0019] The term ‘controller’ or ‘controller unit’ generally refers to a computerized command terminal comprising a collection of sensors and electrical components i.e., to regulate various compressor elements. Compressor controllers include at least one main processing unit with a graphical interface and are adapted to monitor the instrumentation of various compressor parts (e.g., motors, rotors, filters, bearings, valves, pressure sensors, temperature sensors).

[0020] The term ‘processor’ or ‘processing unit’ refers to one or more devices, circuits, and / or processing cores configured to process data, such as computer program instructions, and includes personal computers, desktop computers, laptop computers, message processors, hand-held devices, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, mobile telephones, PDAs, tablets, pagers, routers, switches, and the like.

[0021] The term ‘software’ generally refers to computer-executable instructions, code, data, applications, programs, program modules, or the like maintained in or on any form or type of computer-readable media that is configured for storing computer-executable instructions or the like in a manner that is accessible to a computing device.

[0022] As used herein, reference to any type of machine learning or artificial intelligence may include any type of machine learning algorithm or device, convolutional neural network(s), multilayer neural network(s), recursive neural network(s), recurrent neural network(s), deep neural network(s), decision tree model(s) (e.g., decision trees, random forests, and gradient boosted trees) linear regression model(s), logistic regression model(s), support vector machine(s) (SVM), artificial intelligence device(s), or any other type of intelligent computing system. Any amount of training data may be used (and perhaps later refined) to train the machine learning algorithm to dynamically perform the disclosed operations.

[0023] When introducing elements in the appended claims, the articles “a,” “an,” “the,” and “said” are intended to mean there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.DETAILED DESCRIPTION

[0024] A better understanding of different embodiments of the disclosure may be had from the following description read with the drawings in which like reference characters refer to like elements.

[0025] While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments are in the drawings and are described below. The dimensions, angles, and curvatures represented are to be understood as exemplary and are not necessarily shown in proportion.

[0026] It should be understood, however, there is no intention to limit the disclosure to the specific embodiments disclosed, but on the contrary, the intention covers all modifications, alternative constructions, and equivalents falling within the spirit and scope of the disclosure.

[0027] Figure 1 illustrates various example components of an example compressor system 100 (e.g., a multi-modal compressor system) that may comprise or implement one or more disclosed embodiments. For example, Figure 1 illustrates that a compressor system 100 may include processor(s) 102, storage 104, sensor(s) 110, input / output system(s) 114 (VO system(s) 114), communication system(s) 116, and / or other components. Although Figure 1 illustrates a compressor system 100 as including particular components, one will appreciate, in view of the present disclosure, that a compressor system 100 may comprise any number of additional or alternative components. Furthermore, although some of the components may be illustrated or described as distinct entities, one will appreciate, in view of the present disclosure, that such distinctions are made for the sake of explanation / description only. For example, functionality described herein in association with a particular component may beperformed by a different component or a combination of components as described herein. Accordingly, aspects of the components described herein may be combined with other components or divided into multiple components in accordance with the present disclosure. Additionally, aspects of the present disclosure may be incorporated into oil-free compressors and various types of multi-stage compressors.

[0028] The processor(s) 102 may comprise one or more sets of electronic circuitries that include any number of logic units, registers, and / or control units to facilitate the execution of computer-readable instructions (e.g., instructions that form a computer program). Such computer-readable instructions may be stored within storage 104 (e.g., instructions 106). The storage 104 may comprise physical system memory and may be volatile, non-volatile, or some combination thereof. Furthermore, storage 104 may comprise local storage, remote storage (e.g., accessible via communication system(s) 116 or otherwise), or some combination thereof. Additional details related to processors (e.g., processor(s) 102) and computer storage media (e.g., storage 104) will be provided hereinafter.

[0029] In some implementations, the processor(s) 102 may comprise or be configurable to execute any combination of software and / or hardware components that are operable to facilitate processing using machine learning models or other artificial intelligencebased structures / architectures. For example, processor(s) 102 may comprise and / or utilize hardware components or computer-executable instructions operable to carry out function blocks and / or processing layers configured in the form of, by way of non-limiting example, single-layer neural networks, feed forward neural networks, radial basis function networks, deep feed-forward networks, recurrent neural networks, long-short term memory (LSTM) networks, gated recurrent units, autoencoder neural networks, variational autoencoders, denoising autoencoders, sparse autoencoders, Markov chains, Hopfield neural networks, Boltzmann machine networks, restricted Boltzmann machine networks, deep belief networks, deep convolutional networks (or convolutional neural networks), deconvolutional neural networks, deep convolutional inverse graphics networks, generative adversarial networks, liquid state machines, extreme learning machines, echo state networks, deep residual networks, Kohonen networks, support vector machines, neural Turing machines, and / or others.

[0030] As will be described in more detail, the processor(s) 102 may be configured to execute instructions 106 stored within storage 104 to perform certain actions associated with operation of the compressor system 100. The actions may rely at least in part on data 108 stored on storage 104 in a volatile or non-volatile manner.

[0031] In some instances, the actions may rely at least in part on communication system(s) 116 for receiving data from other components and / or remote system(s) 118, which may include, for example, separate systems or computing devices, sensors, and / or others. The communications system(s) 116 may comprise any combination of software or hardware components that are operable to facilitate communication between on-system components / devices and / or with off-system components / devices. For example, the communications system(s) 116 may comprise ports, buses, or other physical connection apparatuses for communicating with other devices / component s. Additionally, or alternatively, the communications system(s) 116 may comprise systems / components operable to communicate wirelessly with external systems and / or devices through any suitable communication channel(s), such as, by way of nonlimiting example, Bluetooth, ultra-wideband, WLAN, infrared communication, and / or others.

[0032] Figure 1 illustrates that a compressor system 100 may comprise or be in communication with sensor(s) 110 (e.g., to obtain data 108 used to perform acts described herein). Sensor(s) 110 may comprise any device for capturing or measuring data representative of perceivable or detectable phenomena. By way of non-limiting example, the sensor(s) 110 may comprise one or more flow sensors, pressure sensors, hygrometers, image sensors, microphones, thermometers, barometers, magnetometers, accelerometers, gyroscopes, and / or others.

[0033] Furthermore, Figure 1 illustrates that a compressor system 100 may comprise or be in communication with I / O system(s) 114. I / O system(s) 114 may include any type of input or output device such as, by way of non-limiting example, a display, a touch screen, a mouse, a keyboard, a controller, a speaker, and / or others, without limitation.

[0034] Figure 1 also illustrates additional example components of or in communication with the compressor system 100. For instance, Figure 1 illustrates the compressor system 100 comprising a compressor 101 with a compressor motor 120 configured to actuate a compressor element 122 to facilitate gas compression (e.g., compression of ambient air). The compressor motor 120 may take on any suitable form, such as a three-phase induction motor. Similarly, the compressor element 122 may take on any suitable form, such as any type of dynamic compressor (e.g., ejector, radial, or axial compressor) or displacement compressor such as a rotary compressor (e.g., a single rotor such as a vane, liquid ring, or scroll compressor; or a multi-rotor compressor such as a screw, tooth, or blower compressor) or a piston compressor.

[0035] Figure 1 also illustrates various additional components that may operate in conjunction with the compressor motor 120 and the compressor element 122 to facilitate gas compression. Figure 1 illustrates the compressor system as including an inlet filter 124, a sentinel valve 126, air / oil vessel separator 128, thermostatic bypass valve 130, oil filter 132, safety valve 134, oil separator 136, minimum pressure valve 138, solenoid valve 140, after cooler 142, fan 144, oil cooler 146, electronic drain 148, a dryer 150 (the electronic drain 148 can be mounted on the after cooler 142 inimplementations that omit the dryer 150), and a condensate prevention cycle 152. As noted above, one or more of the components shown in Figure 1 may be omitted from a compressor system 100, or alternative components / structures may be utilized in accordance with the scope of the present disclosure.

[0036] Figure 1 also illustrates the compressor system 100 as including a frequency converter 160 configured to connect to a power source 162 and to the compressor motor 120 (as indicated in Figure 1 by dashed lines extending from the power source 162 to the frequency converter 160 and from the frequency converter 160 to the compressor motor 120). As discussed above, the frequency converter 160 controls the operational motor speed of the compressor motor by controlling the frequency and voltage of the compressor motor 120. The frequency converter 160 may comprise a rotary frequency converter, a solid state frequency converter, etc. The power source 162 may comprise a grid-connected power source or an off-grid power source.

[0037] Figure 1 depicts that operation of the frequency converter 160 (and / or the compressor motor 120) may be controlled by a multi-modal drive controller 164 (as indicated in Figure 1 by dashed lines extending from the multi-modal drive controller 164 to the frequency converter 160 and to the compressor motor 120). The multi-modal drive controller 164 may comprise or operate in conjunction with the processor(s) 102 to govern operation of the frequency converter 160 and / or the compressor motor 120.

[0038] According to a first embodiment, the multi-modal controller is configured to operate the frequency converter 160 and / or the compressor motor 120 according to a plurality of operational modes including at least a first compression mode 166 and a second compression mode 168 (as indicated in Figure 1 by solid lines extending from the multi-modal drive controller 164 to the first compression mode 166 and the second compression mode 168). The first compression mode 166 and the second compression mode 168 are associated with different operational motor speed profiles. For example, the first compression mode 166 may comprise a load / unload compression mode, and the second compression mode 168 may comprise a VSD mode. As noted above, the load / unload compression mode may be associated with multiple states, such as a load state (to provide compressed air / gas), an unload state (e.g., idling), or a stop state (e.g., which may be implemented after a period of idling). During the load state (and often the unload state), the compressor motor 120 runs at a substantially constant operational motor speed. This can be accomplished, for example, by configuring the frequency converter 160, via the multi-modal drive controller 164, to impose a substantially constant frequency and voltage for the compressor motor 120 for operation in the load state of the load / unload compression mode, or by bypassing, via the multi-modal drive controller 164, one or more aspects of the frequency converter 160 to allow a constantfrequency and voltage to be supplied to the compressor motor 120 from the power source 162 and / or one or more intervening components.

[0039] As also noted above, a VSD mode is associated with variable operational motor speed of the compressor motor 120, which can be accomplished by causing, via the multi-modal drive controller 164, the frequency converter 160 to dynamically modify the frequency and voltage for operation of the compressor motor 120. The motor speed for the compressor motor 120 (and / or the associated voltage / frequency) may be dynamically determined based upon a demand associated with usage of the compressor system, such as a requested flow of compressed air, a current compressed air pressure of the compressor system 100, etc.

[0040] According to other embodiments, the multi-modal controller is configured to operate the one or more other control components of the compressor system according to a plurality of operational modes including at least a first compression mode and a second compression mode. Such control components may include one or more solenoids, one or more control timers, and / or one or more pressure vessel controls.

[0041] According to embodiments of the present disclosure, an air compressor 101 is provided that has an electrical inverter 165 that is located within an electrical cubicle 123, the electrical cubicle 123 arranged within a housing 119 of the compressor 101. The air compressor 101 also includes a pressure vessel 121 and an element 122 that are also within the housing 119. The electrical cubicle 123 of the air compressor 101 can be located conveniently relative to the pressure vessel 121 and element 122 so that the inverter 165 in the electrical cubicle 123 can provide power to the element 122. In an embodiment, the pressure vessel 121 is provided with the pressure vessel 121 with an outlet port 125 from which the compressed air is selectively discharged. The inverter 165 is directly coupled to the element 122 of the air compressor 101 and does not involve any gears connecting a power source to an element 122. A geared solution involves a configuration such as a geared Y-D startup that incurs large current peaks at startup. The present system does not induce such high peaks, resulting in increased efficiency and less wear and tear on the components. The direct coupling allows for the air compressors to achieve a wide range of pressures by varying the speed at which the element 122 runs. In alternative embodiments, the inverter 165 may be coupled to the air compression element 122 by means of elastic or flexible couplings, belts, gears, or bearings to connect the inverter 165 to the air compression element 122.

[0042] Figure 2 is a plot 200 of pressure in the pressure vessel and power required to achieve that pressure, both as a function of time as defined by the phases of operation: load, unload, and stop, according to the prior art. The plot 200 begins at a loading stop at 202 in which the air compressor is initiated and achieves a steady-state operating condition. 204 represents the beginning of an unloading phase, which is completedat 206 which represents the beginning of a stop phase. At 208 the cycle continues with a second loading phase, also known as a reloading phase, which may be different than the initial loading phase beginning at 202. In the first loading phase, block 212 represents the power required to achieve the desired pressure in a pressure vessel of the air compressor, and a line 201 represents the pressure in the vessel. The shortcomings of this cycle in an air compressor having a gear drive and an indirect coupling to the power source will be described below in greater detail.

[0043] The initial loading operation is characterized by a sharp increase in pressure and power required to achieve a quasi-steady state status. At the unloading phase at 204, the pressure sharply, then continuously declines. The power required in this phase is characterized by two blocks: first, a transient loss block at 214, and an unloading power 216. The unloading power is not necessarily a loss, but the transient losses are and can be avoided by the systems and methods described herein that are the subject of this disclosure.

[0044] At 206 a stop phase begins in which the unloading process is complete and the pressure drops to zero inside the pressure vessel. The transient losses continue in this phase at 217. In conventional geared air compressors without an internal inverter, these losses are difficult to avoid. One reason is that at 208 when the next load phase begins, if there is pressure in the pressure vessel, a high amount of start-up current is required to load the system as shown by ramp 218. These peaks of current equate to a higher resource cost and higher losses overall. The plot 200 finishes at 210 with a fully loaded phase using power at 220 and the pressure returned to the pressure vessel.

[0045] Figure 3 is a plot 221 of pressure in the pressure vessel and power required to achieve that pressure, both as a function of time as defined by the phases of operation: load, unload, and stop, according to the present disclosure including an internal inverter directly coupled to the element. The initial load phase at 202 may be identical to the system of Figure 2, characterized by a steep ramp of pressure and associated power to achieve it and a block 222 representing power consumed to achieve this pressure, followed by a quasi-steady state operating period. At 204 the unloading phase begins and is characterized by a decrease in pressure in the vessel, some transient losses at 224, and an unloading power at 226. In the stop phase at 206 however, the pressure in the pressure vessel is maintained at a diminished, non-zero level that is slightly less than the pressure during a load phase. In some embodiments the pressure in this phase is approximately 45% of the pressure at a fully loaded phase. In some embodiments the pressure in this phase is in the range of 25%-100% of the pressure during the load phase.

[0046] Notably the transient losses shown in Figure 2 at 217 are not present in Figure 3. The pressure vessel can be properly sealed to maintain the pressure during a stopphase. In some embodiments an air compressor according to this disclosure can include a timer and a routine to expel the pressure in the vessel after a predetermined time passes at the elevated pressure. The predetermined time can be any arbitrary time period such as five minutes. An expiration of the predetermined time can alert nearby individuals that the time has expired and that the pressure will be expelled. The pressure can be expelled slowly and safely to avoid injury to anyone who may be nearby when the timer expires. In some embodiments an external event or condition can cause the blow-off to begin, such as condensation, humidity, or air pressure. In some embodiments the pressure is never blown off until the next phase begins or the device is decommissioned.

[0047] At 208 a second loading phase can begin and is characterized by a much smaller power requirement 228 than at 218 in Figure 2. The power required to achieve this pressure is shown at 230. In a system with an internal inverter that is coupled directly to the element, the pre-existing pressure is not an impediment to be overcome; rather, it is ground already covered that need not be covered again. It is a head start for the compressor. The result is lower current draws, less power required, a shorter time required to reach a fully loaded state, and overall higher efficiency. At 210 the second loading phase ends and can be followed by a second unload phase at 204 and the cycle continues.

[0048] It is to be understood that not necessarily all objects or advantages may be achieved under any embodiment of the disclosure. Those skilled in the art will recognize that the claimed compressor device may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without achieving other objects or advantages as taught or suggested herein.

[0049] The skilled artisan will recognize the interchangeability of various disclosed features. Besides the variations described herein, other known equivalents for each feature can be mixed and matched by one of ordinary skill in this art to build and use a compressor device under principles of the present disclosure. For example, an inverter of the disclosed fixed-speed compressor may permit discrete speed regulation of a motor with several fixed speeds. It will be understood by the skilled artisan that the features described herein may be adapted to other methods and types of air compressor devices / applications.

[0050] It is intended that the present disclosure should not be limited by the disclosed embodiments described above and may be extended to other applications that may employ the features described herein.

Claims

Claims

1. An air compressor (101), comprising: a housing (119) including a pressure vessel (121) and an electrical cubicle (123); at least one air compression element (122) within the housing (119) and being configured to compress air in the pressure vessel (121); an inverter (165) in the electrical cubicle (123) and coupled to the at least one air compression element (122), the inverter (165) being configured to operate the at least one air compression element (122) to compress the air into the pressure vessel (121) in at least three phases: load, unload, and stop; wherein: during the load phase, an inverter driven motor (120) causes the at least one air compression element (122) to compress air into the pressure vessel (121) to a first pressure level, the pressure vessel (121) having an outlet port (125) from which the compressed air is selectively discharged; during the unload phase, the compressed air in the pressure vessel(121) is internally recirculated and / or blown-off to reduce the air pressure in the pressure vessel (121) to approach an atmospheric pressure at a second pressure level that is lower than the first pressure level and power consumption is operated at a diminished rate; during the stop phase, the at least one air compression element(122) is stopped and pressure within the pressure vessel (121) is maintained; and during a subsequent load phase, the inverter (165) starts up without causing a spike in drawn current.

2. The air compressor (101) of claim 1, further comprising an inlet valve and a minimum pressure valve (MPV), wherein the MPV is closed during an unload phase due to external pressure being higher than pressure within the pressure vessel (121), and wherein the inlet valve is closed during a stop phase.

3. The air compressor (101) of claim 1 wherein during the stop phase, the air pressure in the pressure vessel (121) is maintainedat a diminished, non-zero level that is slightly less than the first pressure level.

4. The air compressor (101) of claim 1 wherein during the stop phase, after a predetermined time elapses or a predetermined condition is satisfied, pressure within the pressure vessel (121) is released, said predetermined condition being dependent on condensation, humidity, or air pressure.

5. The air compressor (101) of claim 1 wherein during the unload and stop phase pressure within the pressure vessel (121) is approximately 10% to 25% of a maximum pressure level of the compressor (101).

6. The air compressor (101) of claim 2 wherein one or more of the inlet valve and the MPV is a passive valve.

7. The air compressor (101) of claim 1 wherein the at least one air compression element (122) is located at least partially within the pressure vessel (121).

8. A method for operating an air compressor (101) having an internal inverter (165) providing power to an air compression element (122), the method comprising: loading a pressure vessel (121) of the air compressor (101) with compressed air from the air compression element (122) to a first pressure level; discharging the compressed air from the pressure vessel (121); unloading compressed air from the pressure vessel (121), wherein unloading comprises sealing the pressure vessel (121) to maintain air pressure within the pressure vessel (121) and recirculating air within the pressure vessel (121) and / or blowing off air to reduce the air pressure within the pressure vessel (121) to approach an atmospheric pressure at a second pressure level that is lower than the first pressure level; stopping the air compression element (122) using the internal inverter (165) with the air pressure maintained within the pressure vessel (121) at a second pressure level lower than the first pressure level; and loading the pressure vessel (121) of the air compressor (101) with compressed air from the air compression element (122) by raising the pressure from the second level to the first level and without dropping the air pressure below the second air pressure.

9. The method of claim 8 wherein the second pressure level is in a range of 25-100% of the first pressure level.

10. The method of claim 8 wherein the first level is in a range of 4-13 bars, and wherein the second level is in the range of 1-4 bars.

11. The method of claim 8 wherein sealing the pressure vessel (121) comprises passively sealing the pressure vessel (121) using a check valve.

12. The method of claim 8 wherein the internal inverter (165) is located within a housing (119) of the air compressor (101).

13. The method of claim 12 wherein the internal inverter (165) is located within an electrical cubicle (123) of the housing (119) that is separate from the pressure vessel (121).

14. The method of claim 13 wherein the internal inverter (165) is mechanically coupled to the air compression element (122) from the electrical cubicle (123) to the pressure vessel (121).

15. The method of claim 8, further comprising after a predetermined time elapses during which the air compressor (101) is not started, discharging the air pressure from the pressure vessel (121).

16. A multi-modal compressor system (100) comprising: an air compressor (101); a processor (102); a memory (104) configured to store instructions (106) that, when executed by the processor (102), causes the processor (102) to perform a plurality of instructions (106), the instructions (106) comprising: executing a loading phase during which an internal inverter (165) located within a housing (119) of the air compressor (101) powers an air compression element (122) that pressurizes air into a pressure vessel (121), the pressure in the pressure vessel (121) reaching a first pressure level; executing an unloading phase during which compressor power consumption is reduced by recirculating and / or blowing-off the compressed air and the pressure is reduced to a second pressure level lower than the first pressure level, wherein during the unloading phase the pressure vessel (121) is sealed to maintain the pressure within the pressure vessel (121) at the second pressure level;executing a stop phase during which the internal inverter (165) is stopped, the pressure in the pressure vessel (121) is maintained at the second pressure level; and executing a reloading phase during which the internal inverter (165) powers the air compression element (122) to elevate the pressure from the second pressure level to the first pressure level without permitting the pressure in the pressure vessel (121) to fully dissipate.

17. The system of claim 16 wherein the pressure vessel (121) comprises one or more check valves on outlet ports to maintain pressure in the pressure vessel (121) during the unload and stop phases.

18. The system of claim 16 wherein the second pressure level is at least 35% of the first pressure level.

19. The system of claim 16 wherein the pressure vessel (121) is configured to release the pressure in the pressure vessel (121) after a predetermined time period elapses during the stop phase.

20. The system of claim 16 wherein the pressure vessel (121) is configured to release the pressure in the pressure vessel (121) in response to one or more external conditions during the stop phase.

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