Dynamic current-limiting motor starting device for limited power supply system

Abstract

Apparatus and associated methods relate to power management systems for initializing electrical appliances under limited current conditions. A starting circuit system includes a load and an AC source with a rectifier coupled to the AC source and a unipolar voltage node. An inverter has an input coupled to the unipolar voltage node and an output coupled to an inverter output node. A bypass switch connects to the load, AC source, and inverter output node. A controller recognizes when the load cannot be served by the AC source, starts the load by controlling the inverter to generate an output voltage waveform and connecting the bypass switch to route power from the inverter to the load, then transfers control back to the AC source by transitioning the bypass switch to connect the AC source to the load. Embodiments enable electric motors to be started by power sources with limited current capacity.

Description

[0001] TPL Docket No.: 635-02-WO DYNAMIC CURRENT-LIMITING MOTOR STARTING DEVICE FOR LIMITED POWER SUPPLY SYSTEM TECHNICAL FIELD [1] Various embodiments relate generally to power management systems for starting electrical appliances under limited current conditions. BACKGROUND [2] Electric motor systems are widely used across numerous applications, from industrial machinery to consumer appliances and power tools. These systems typically rely on alternating current (AC) power sources to operate, converting electrical energy into mechanical motion through electromagnetic principles. As electric motor technology has evolved, various control and power management approaches have been developed to optimize motor performance, efficiency, and compatibility with different power supply configurations. [3] Power management systems for electric motors encompass a range of technologies designed to regulate voltage, frequency, and current delivery to motor loads. These systems may include rectifiers for converting AC power to direct current (DC), inverters for converting DC back to variable-frequency AC, and control circuits that monitor and adjust power delivery parameters. Variable frequency drives represent one category of power management technology that can modify the frequency and voltage supplied to motors, enabling control over motor speed and torque characteristics. Such systems may be employed in industrial settings where precise motor control is desired. SUMMARY [4] Apparatus and associated methods relate to power management systems for starting electrical appliances under limited current conditions. In an illustrative example, a variable frequency AC power system having an adaptive initialization conditions power supply automatically detects load demanding excessive inrush current via a load sensing circuit and, upon detection, immediately reduces output voltage and frequency to reduce input current to the capacity of the power source. For example, the system controllably and automatically ramps up the voltage and the frequency in a prescribed ratio so as to limit the input current to a user-selected current limit setting. Various embodiments may advantageously provide a dynamic power management solution that enables electric TPL Docket No.: 635-02-WO motors to be started by power sources with limited current capacity without requiring oversized generators or inverters. [5] In some examples, a starting circuit system may include a load and an AC source paired with the load. The system may include a rectifier having an input coupled to the AC source and an output coupled to a unipolar voltage node. An inverter may have an input coupled to the unipolar voltage node and an output coupled to an inverter output node. A bypass switch may include an output node configured to connect to the load, a first bypass input configured to connect to the AC source, and a second input configured to connect to the inverter output node. A controller may be configured to recognize when the load cannot be served by the paired AC source, start the load by controlling the inverter to generate an output voltage waveform and connecting the bypass switch to route power from the inverter to the load, and transfer control of the load back to the AC source by transitioning the bypass switch to connect the AC source directly to the load. The controller may be configured to receive an input monitor signal representative of a phase of the AC source and an output monitor signal representative of an output current supplied to the load, and may generate an inverter control signal configured to cause the inverter to generate the output voltage waveform substantially in phase with the input monitor signal. In a first mode, the bypass switch may connect the second input to the bypass output node and the controller may regulate the output current supplied to the load in response to the output monitor signal according to a predetermined voltage to frequency ratio, and in a second mode, the bypass switch may connect the first input to the bypass switch output node. When transitioning from the first mode to the second mode, the bypass switch may disconnect from the inverter output node before connecting directly to the AC source, and the controller may be configured to transition from the first mode to the second mode in response to predetermined conditions being met. [6] Various embodiments may achieve one or more advantages. For example, some embodiments may advantageously enable standard tools and appliances to be used with smaller generators or inverters without requiring modifications to the tools themselves. Some embodiments may advantageously enable the use of smaller generators or battery- inverter systems, potentially eliminating noise and pollution when using battery-inverter systems that can be activated only during tool operation. Some implementations may advantageously eliminate the need for oversized power supply equipment, reducing initial costs and operating expenses. Some embodiments may advantageously provide higher starting torque compared to traditional soft-start methods while drawing lower TPL Docket No.: 635-02-WO current. Some embodiments may, for example, advantageously function as a universal power conditioner that can be seamlessly used with a wide variety of inductive loads without complex programming or customization. Some embodiments may advantageously reduce system complexity by eliminating dedicated control circuitry for variable frequency drives. [7] The details of various embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS [8] FIG. 1 depicts an exemplary variable frequency alternating current power system (VFACPS) employed in an illustrative use-case scenario. [9] FIG.2A, FIG.2B, and FIG.2C depict exemplary frequency, current, and voltage response of the VFACPS when it is coupled to a motor load exceeding a power source capacity.

[0010] FIG.3 is a flowchart illustrating an exemplary configuration method.

[0011] FIG.4 is a flowchart illustrating an exemplary operation method.

[0012] FIG. 5 illustrates a block diagram of an exemplary variable frequency alternating current power system with bypass switching capabilities.

[0013] FIG.6A, FIG.6B, and FIG.6C illustrate exemplary frequency, current, and voltage responses of a device without power management capabilities.

[0014] FIG.7A, FIG.7B, and FIG.7C illustrate exemplary frequency, current, and voltage responses of a device with power management capabilities.

[0015] FIG. 8 illustrates a block diagram of an exemplary variable frequency alternating current power system with DC power source configuration.

[0016] Like reference symbols in the various drawings indicate like elements. DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0017] FIG. 1 depicts an exemplary variable frequency alternating current power system (VFACPS) employed in an illustrative use-case scenario. In the depicted example, a VFACPS 100 includes an adaptive initialization conditions power supply (AICPS 105). For example, the AICPS 105 may be a single power supply enclosed within a single housing pluggable to an alternating current (AC) input. For example, the AICPS 105 may receive a limited AC power input 110. For example, the VFACPS 100 may be used in scenarios with limited grid power (e.g., off-grid, in remote environments). For example, the limited AC power input 110 may supply to the AICPS 105 a single-phase current at a TPL Docket No.: 635-02-WO predetermined frequency (e.g., 50 Hz, 60Hz) at a predetermined voltage (e.g., 120V, 220- 240V).

[0018] In some examples, the VFACPS 100 may include a site (e.g., construction sites, camping, off-grid homes, remote village). In this example, the VFACPS 100 includes loads 115. For example, the loads 115 may include high-power electric loads. For example, the loads 115 may include power tools. For example, the loads 115 may include one or more electric motors. For example, the loads 115 may include one or more pumps. For example, the loads 115 may include one or more condensers (e.g., heat transfer systems). As an illustrative example without limitation, the loads 115 may include one or more air compressors, power tools (e.g., saws or drills, heating elements, ventilation fans, lighting systems, refrigeration units).

[0019] In some implementations, the loads 115 may include an inductive load. For example, the loads 115 may include a large inrush current requirement. Various embodiments may advantageously prevent an unmatched inrush current demand of the loads 115 during startup when the Load draws its highest inrush current. For example, the VFACPS 100 may ramp up frequency and / or voltage to prevent a large inrush current demand at the loads 115.

[0020] As shown, the loads 115 are connected (e.g., in parallel) to the AICPS 105 through a power distribution unit (PDU 120). For example, the PDU 120 may include an extension cord to distribute power to the loads 115. As shown, the PDU 120 is connected to a load sensing circuit (LSC 125) of the AICPS 105. In some implementations, the LSC 125 may generate power condition measurements (e.g., current measurement, voltage measurement) of the PDU 120. Based on the power condition measurements, the AICPS 105 may manage starting current for high-power electric loads (e.g., the loads 115).

[0021] In this example, the AICPS 105 includes a rectifier 130. For example, the rectifier 130 may be configured to convert incoming AC power into DC electricity. In this example, the AC power may be supplied by the limited AC power input 110 (e.g., a standard AC power line from a distribution network is a common source). In some examples, the rectifier 130 may receive power (e.g., in addition or alternatively) from a local inverter. For example, the rectifier 130 may receive AC power from an inverter converting DC power (e.g., batteries, solar panels) into AC power. In some examples, the rectifier 130 may receive power from a generator. For example, the VFACPS 100 may be operating off- grid. For example, the AC power source may include an output of a (e.g., gasoline, diesel) generator. TPL Docket No.: 635-02-WO

[0022] The AICPS 105 includes an inverter 135, a DC link 140, and a controller 145. The rectifier 130 is connected to the inverter 135 via the DC link 140. For example, the inverter 135 may include a Variable Frequency Drive (VFD). In some implementations, the inverter 135 may be configured to regulate an output voltage and frequency of the AICPS 105 to the PDU 120 based on a control signal received from the controller 145. For example, the LSC 125 may generate a signal representing instantaneous current at the PDU 120. For example, the controller 145 may generate a control signal based on the signal received from the LSC 125 to drive the inverter 135.

[0023] As shown, the controller 145 includes an adaptive system initialization module (ASIM 150) and a user-selected current limit setting (user-selected CLS 155). In some implementations, the controller 145 may manage an overall operation of the AICPS 105. During a start-up operation, for example, the controller 145 may initialize the current flow at the PDU 120 based on the ASIM 150 and the user-selected CLS 155. For example, the user-selected CLS 155 may allow users to define the maximum allowed current output of the device, as determined by the current rating of the tool being powered. For example, the maximum allowed current may be set according to the current rating of the supply. Various embodiments may advantageously manage a high starting current for electric motor loads (e.g., the inrush current demand of the loads 115) by providing a dynamic power management solution (e.g., the ASIM 150) during startup. For example, the AICPS 105 may be configured to adaptively be used with limited power sources (e.g., the limited AC power).

[0024] In some implementations, the ASIM 150 may include a demand-based frequency and voltage reduction module. For example, the demand-based frequency and voltage reduction module may be configured to operate the AICPS 105 initially at nominal frequency and voltage. For example, the demand-based frequency and voltage reduction module may then dynamically reduce the frequency and voltage only as necessary to limit the current to a user-defined and / or pre-programmed desired level. For example, the demand-based frequency and voltage reduction module may advantageously reduce disruption to the user experience by maintaining nominal voltage and frequency as much as possible.

[0025] In some implementations, induction motors commonly used in consumer-grade appliances and power tools, during startup, may require a high inrush current. In some examples, directly connecting these motors to an AC power source (e.g., the limited AC power input 110, a generator, an inverter) may result in current surges significantly TPL Docket No.: 635-02-WO exceeding an available source capacity. For example, some current surges may lead to system faults. In some examples, oversized power supply equipment may be used to accommodate the inrush current demand. For example, the oversized equipment may have high initial costs and / or increase operating expenses due to decreased overall system efficiency. In some examples, when the limited AC power is supplied by a generator, the need to handle starting current surges may result in unnecessary generator runtime, leading to increased noise, pollution, and fuel consumption.

[0026] As an illustrative example without limitation, the loads 115 may include electric power tools and appliances frequently used in off-grid situations (e.g., construction sites, campgrounds, off-grid residences and communities, outdoor events) where the only available power source is a generator or inverter. For example, the loads 115 may draw high starting currents. For example, the loads 115 may draw exceeding 10 times their steady-state current.

[0027] In some implementations, the AICPS 105 may attempt to power the load at nominal voltage and frequency when an electric load is connected. For example, the AICPS 105 may auto-start when one or more of the loads 115 are detected. For example, when a load current is detected, the AICPS 105 may immediately deliver a full-load or near full-load frequency. For example, the ASIM 150 may be configured to automatically regulate the inverter 135 to supply AC power at 30Hz when the load is detected.

[0028] In some implementations, the AICPS 105 may be always on. For example, when the controller 145 receive the signal indicating a load current exceeding the limited AC power input 110, the AICPS 105 may ramp down the frequency and / or voltage until the load current is matched to the maximum power supply available defined by the limited AC power input 110 and / or the user-selected CLS 155.

[0029] The AICPS 105 may, for example, be pluggable into a Ground Fault Circuit Interrupter (GFCI) circuit. The VFD load delivery device may include a pluggable GFCI circuit receptacle. A normal powered appliance (e.g., power tool), for example, may be plugged into the AICPS 105 through the GFCI circuit, and the AICPS 105 may automatically ramp the electric power delivered to match the load to power supply.

[0030] In some implementations, the AICPS 105 may, for example, have multiple receptacles. The ASIM 150 may be configured to start supplying (e.g., only) a first load in a ramp mode, for example, then operate in a bypass mode once the output voltage and frequency have reached nominal values. The AICPS 105 may then, for example, permit a TPL Docket No.: 635-02-WO second load to be connected and started in the ramp mode with the first load being operated in the bypass mode.

[0031] In the case of small loads (e.g., an electric lamp, laptop computer), the load current may remain below a predefined current capacity of both the AICPS 105 and the limited AC power input 110. In some implementations, the AICPS 105 may then maintain nominal voltage and frequency at its output. In the case of a motor-driven tool or appliance (e.g., power tools), the starting current may exceed the current capacity of the limited AC power input 110 and / or the AICPS 105. In some implementations, the LSC 125 may include a fast response current sensing circuit. For example, when the LSC 125 senses the current flowing to the load reaching or exceeding the lesser of the current capacity of the limited AC power input 110 and / or the current capacity of the AICPS 105 (e.g., the user-selected CLS 155), the AICPS 105 may automatically decrease the output frequency and voltage at the inverter 135 to limit the load current.

[0032] In some implementations, in the ramp mode, the output frequency and voltage of the inverter 135 may be controlled by the controller 145 at a predetermined V / f ratio predefined by the ASIM 150. In some examples, the ramp at the predetermined V / f ratio may be preset at a maximum rate possible without exceeding the maximum available current. For example, the ramp may continue until the output voltage and frequency reach their nominal values. If the ramp must be discontinued based on the maximum available current defined by, for example, the user-selected CLS 155, the AICPS 105 may shut off after a user settable delay. In some embodiments, the AICPS 105 may generate an indication to the user that the connected load exceeds the capacity.

[0033] The AICPS 105 may, for example, include a feedback indicator. The AICPS 105 may, for example, be plug and play. The AICPS 105 may, for example, be configured to a single phase. The AICPS 105 may, for example, provide a static and / or dynamic ramp rate as a function of present current and a maximum current. Various embodiments may advantageously provide a small, pluggable power management unit to advantageously match loads to available power sources. The AICPS 105 may, for example, permit usage of renewable power sources (e.g., solar power) to power normal loads (e.g., power tools). The AICPS 105 may, for example, permit usage of a smaller generator by matching available generator power to the load by reducing inrush current.

[0034] For example, when the AICPS 105 is activated, the controller 145 may be configured to control the inverter 135 to generate output at nominal frequency and voltage. Upon detecting a load that would cause the current to exceed the maximum allowed TPL Docket No.: 635-02-WO current, for example, the controller 145 may operate in the ramp mode by reverting to a low frequency and voltage (e.g. 30% of nominal). In the ramp mode, the controller 145 may operate using the ASIM 150 by limiting current to the user-selected CLS 155. In ramp mode, the output voltage and frequency, for example, may be ramped from the low frequency and voltage toward nominal values based on a ramp rate defined in the ASIM 150 (e.g., to not exceed the maximum allowable device current). In some examples, the AICPS 105 may be configured to operate in the ramp mode only briefly (e.g., under two seconds). Various embodiments may advantageously reduce disruption to the user's experience of operating the tool. When, for example, the load current reaches nominal voltage and frequency values, the controller 145 may operate in the bypass mode to maintain the output voltage and frequency. In some implementations, the controller 145 may be configured to operate in the bypass mode until another load or condition is detected to trigger the controller 145 to operate in the ramp mode.

[0035] FIG. 2A, FIG. 2B, and FIG. 2C depict exemplary frequency, current, and voltage response of the VFACPS when it is coupled to a motor load exceeding a power source capacity. For example, the graphs depicted in FIGS.2A-C may show an exemplary output curve upon a motor load connected to the AICPS 105 is started. For example, when the motor load starts, the inrush current demand may exceed a capacity of the limited AC power input 110.

[0036] In some implementations, controller 145 may detect a triggering condition from the LSC 125 at the VFACPS 100. For example, the controller 145 may transit from a bypass mode 205 into a ramp mode 210. For example, the controller 145 may transit from the bypass mode 205 to the ramp mode 210 when an inrush current is detected to be exceeding the user-selected CLS 155. For example, the controller 145 may determine that the inrush current is detected to be exceeding the user-selected CLS 155 based on a predetermined pattern of the signal received from the LSC 125.

[0037] FIG. 2A shows an exemplary frequency response 200 when the 105 / / transition from the bypass mode 205 to the ramp mode 210. For example, after transitioning to the ramp mode 210, the controller 145 may regulate an output frequency to a starting frequency 215 lower than a nominal frequency 220. As shown in FIG. 2B, a current response 225 at ramp mode 210 may be regulated to maintain at a limited current level 230 less than a maximum current of the limited AC power input 110 and / or the user-selected CLS 155. As shown in FIG.2C, after transitioning to the ramp mode 210, the controller 145 may regulate an output voltage 235 to a starting voltage 240 lower than a nominal frequency 245. TPL Docket No.: 635-02-WO

[0038] In some examples, the AICPS 105 may function as a universal power conditioner. For example, the AICPS 105 may seamlessly be used with a wide variety of inductive loads (e.g., motors) without any need for complex programming or customization. In some embodiments, the AICPS 105 may mitigate extensive setup procedures and / or user programming by operating with only 2 to 3 user-selected parameters. In some implementations, the AICPS 105 may increase starting torque offered to the loads 115. For example, AICPS 105 may adjust motor performance during startup based on the user- selected CLS 155. In some examples, the user-selected CLS 155 may allow tools to reach full operational speed more quickly and efficiently.

[0039] In some implementations, the AICPS 105 may reduce current draw from the limited AC power input 110 while maintaining equivalent torque output at the loads 115. Various embodiments may advantageously allow for smoother operation without exceeding current capacity. In some implementations, the AICPS 105 may remove dedicated control circuitry for VFDs. Various embodiments may advantageously reduce system complexity. In some implementations, the AICPS 105 may provide an interface for standard tools and / or appliances to be used with a smaller generator or inverter. In some implementations, the AICPS 105 may draw power only during tool operation. For example, when the loads 115 are required to be used intermittently, the AICPS 105 may allow for deactivation during idle time of the loads 115. Various embodiments may promote energy efficiency compared to systems having a continuously running generator. Various embodiments may advantageously reduce fuel consumption, noise, and / or other pollution associated with generators running idle.

[0040] FIG.3 is a flowchart illustrating an exemplary configuration method. For example, the configuration method may be performed by an engineer using the AICPS 105. In some embodiments, the AICPS 105 may include a user interface (e.g., a touch screen, knobs, a keypad, push buttons) configured to receive user input. In this example, a method 300 begins when a nominal frequency and voltage are received by the controller 145 in step 305. For example, the nominal frequency and voltage may be preset in the VFACPS 100 for standard operating conditions based on physical properties of the limited AC power input 110.

[0041] In step 310, a user-selected current limit setting is received by the user-selected CLS 155. For example, the user may input the user-selected CLS 155 for the loads 115 based on the tools’ current rating. In step 315, a user-settable delay is received by the controller 145. For example, the user may set a delay time that dictates how long the TPL Docket No.: 635-02-WO VFACPS 100 should wait before shutting down after detecting a current exceeding the user-selected CLS 155.

[0042] Next, a ramp down frequency and / or voltage is received by the ASIM 150 in step 320. For example, the user may configure the initial frequency and voltage (e.g., the starting frequency 215 and / or the starting voltage 240) to which the VFACPS 100 should drop in response to an overcurrent condition (e.g., a triggering condition). In step 325, a V / f ratio is received, and the method 300 ends. For example, the ASIM 150 may be configured to ensure that the voltage and frequency ratio is maintained according to the load requirements during ramp-up to avoid exceeding the current limit.

[0043] FIG.4 is a flowchart illustrating an exemplary operation method 400. For example, the method 400 may be performed by the controller 145. In this example, the method 400 begins in step 405 when an output having a nominal frequency and voltage is generated. For example, the controller 145 may initiate the output at the (standard) nominal operating conditions of the VFACPS 100 based on the specifications of the limited AC power input 110.

[0044] At a decision point 410, it is determined whether a trigger condition has been reached. For example, the controller 145 may receive a signal from the LSC 125 indicating that the inrush current exceeds the user-selected CLS 155. If no trigger condition is detected, the method 400 returns to step 405.

[0045] If a trigger condition is detected, in step 415, the current output is reduced to a user- selected level by setting the voltage and frequency of the output to a predetermined starting point. For example, the controller 145 may automatically adjust the inverter 135 to reduce the output to a lower frequency and voltage (e.g., the starting frequency 215 and / or the starting voltage 240) For example, the starting frequency 215 and / or the starting voltage 240 may be defined by the user-selected settings in the ASIM 150 in the method 300.

[0046] In step 420, a ramp rate is dynamically generated based on a sensed current from the LSC 125. For example, the ASIM 150 may continuously monitor the load current and adjust the ramp rate to gradually increase the output frequency and voltage without exceeding the maximum allowable current defined by the user-selected CLS 155.

[0047] At a decision point 425, it is determined whether nominal conditions have been reached. For example, the controller 145 may assess whether the output has returned to the nominal frequency and voltage based on the signal received from the LSC 125. If nominal conditions are not reached, the step 420 is repeated. If nominal conditions are reached, the step 405 is repeated. TPL Docket No.: 635-02-WO

[0048] FIG. 5 illustrates a block diagram of an exemplary variable frequency alternating current power system with bypass switching capabilities. In the depicted example, a VFACPS 500 includes an AC power source 505 connected to a rectifier 510. The AC power source 505 may include various sources such as a utility grid connection, a local inverter output, or a generator output in off-grid scenarios. The rectifier 510 may convert the incoming AC power into DC electricity and may be connected to an inverter 515 through a DC link. An optional DC input 525 may be provided to allow direct connection to DC sources such as solar battery systems, eliminating the need for a separate inverter when using DC power sources.

[0049] In some examples, the system may include voltage / frequency / current signals 520 that are monitored from the input side and provided to a ramp control 530. The ramp control 530 may manage the overall operation of the system, including control of the inverter 515 and a bypass switch 535. The bypass switch 535 may selectively connect either the inverter 515 output or the AC power source 505 directly to a load 550 through connections labeled L1 and N. Voltage / frequency / current signals 545 may be monitored from the load side and fed back to the ramp control 530 to provide closed-loop control of the system operation.

[0050] The bypass switch 535 may include a contactor assembly or relay system that enables seamless switching between the inverter output and direct AC source connection. When the system detects that a load cannot be served by the paired AC source due to excessive inrush current demands, the bypass switch 535 may route power from the inverter 515 to the load 550. Once the load has been successfully started and reaches nominal operating conditions, the bypass switch 535 may transfer control back to the AC power source 505 by connecting the AC source directly to the load, thereby bypassing the inverter circuitry.

[0051] FIG.6A, FIG.6B, and FIG.6C illustrate exemplary frequency, current, and voltage responses of a device without power management capabilities. These figures demonstrate the problematic behavior that occurs when conventional power sources attempt to start high-inrush-current loads without appropriate current limiting.

[0052] FIG. 6A shows a frequency response 600 over time, depicting a bypass mode 605 followed by a ramp mode 610. Initially, the system operates at nominal frequency 615 of approximately 60 Hz. However, when the excessive load is applied around 200 milliseconds, the frequency drops precipitously to frequency level 620 near zero Hz, indicating system failure or shutdown due to overload conditions. TPL Docket No.: 635-02-WO

[0053] FIG. 6B shows the corresponding current response 625 during the same time period. The system initially operates in bypass mode 605 with minimal current draw. When the load is applied, there is a sharp current spike reaching current level 630 of approximately 12 amperes, which exceeds the capacity of the power source and causes the system to trip or shut down, as evidenced by the current returning to near zero after the brief spike.

[0054] FIG.6C depicts the output voltage 635 behavior during this failed starting attempt. The system initially maintains nominal voltage 640 of approximately 120 volts during bypass mode 605. However, when the excessive load is applied, the voltage collapses to voltage level 645 near zero volts, confirming that the power source cannot sustain the load demand and results in system shutdown.

[0055] FIG.7A, FIG.7B, and FIG.7C illustrate exemplary frequency, current, and voltage responses of a device with power management capabilities. These figures demonstrate the controlled starting behavior achieved through the adaptive power management system described herein.

[0056] FIG.7A shows a frequency response 700 that transitions from bypass mode 705 to ramp mode 710 when an excessive load is detected. Initially, the system operates at nominal frequency 715 of approximately 60 Hz. Upon detecting a load that would cause excessive current draw, the system automatically reduces the output frequency to starting frequency 720 of approximately 20 Hz. The frequency is then gradually ramped up over time in a controlled manner until it reaches the nominal frequency 715, allowing the load to start without exceeding current limitations.

[0057] FIG. 7B shows the corresponding current response 725 during the controlled starting process. The system maintains the current at current level 730 of approximately 8 amperes throughout both the bypass mode 705 and ramp mode 710. This demonstrates that the power management system successfully limits the current to a predetermined threshold that is within the capacity of the power source, preventing system overload while still providing sufficient power to start the load.

[0058] FIG. 7C depicts the output voltage 735 behavior during the controlled starting sequence. The system initially operates at nominal voltage 740 of approximately 120 volts during bypass mode 705. When transitioning to ramp mode 710, the voltage is reduced to starting voltage 745 of approximately 40 volts. The voltage is then gradually increased in coordination with the frequency ramp, maintaining a predetermined voltage-to-frequency ratio until both voltage and frequency reach their nominal values. TPL Docket No.: 635-02-WO

[0059] The coordinated ramping of voltage and frequency according to a predetermined V / f ratio may provide several advantages. This approach may maintain proper motor flux levels during startup, ensuring adequate starting torque while limiting current draw. The ramp rate may be dynamically adjusted based on the monitored current to ensure that the current limit is not exceeded while minimizing the time required to reach full operating conditions.

[0060] FIG. 8 illustrates a block diagram of an exemplary variable frequency alternating current power system with DC power source configuration. In this embodiment, a VFACPS 800 includes a DC power source 805 that provides power to multiple system components. The DC power source 805 may include batteries, solar panels, fuel cells, or other DC energy sources commonly used in off-grid or portable applications.

[0061] In some examples, the system may include a nominal conditions inverter 810 that converts DC power to AC power for supplying other loads 855 under normal operating conditions. A DC / DC converter 815 may be provided to condition the DC power from the DC power source 805 for use by a ramping inverter 825. The DC / DC converter 815 may provide voltage regulation, isolation, or other power conditioning functions as needed for optimal operation of the ramping inverter 825.

[0062] Voltage / frequency / current signals 820 may be monitored from the DC power source 805 and provided to a control system. A ramp control 830 may manage the operation of the ramping inverter 825, which is specifically configured to provide the controlled voltage and frequency ramping functionality described herein. The ramping inverter 825 may operate independently of the nominal conditions inverter 810, allowing the system to simultaneously serve other loads 855 through the nominal conditions inverter 810 while providing controlled starting power to a motor load 850 through the ramping inverter 825.

[0063] A bypass switch 835 may be positioned between the ramping inverter 825 and the motor load 850, receiving bypass control signals 840 from the control system. The bypass switch 835 may connect the motor load 850 to either the ramping inverter 825 during startup operations or to the nominal conditions inverter 810 once the motor load 850 has reached steady-state operation. Voltage / frequency / current signals 845 may be monitored from the motor load 850 side and fed back to the control system to provide closed-loop control.

[0064] This dual-inverter configuration may provide several advantages in DC-powered systems. The nominal conditions inverter 810 may be optimized for steady-state operation and efficiency, while the ramping inverter 825 may be specifically designed for the TPL Docket No.: 635-02-WO transient conditions encountered during motor starting. The system may automatically detect when the motor load 850 cannot be served by the nominal conditions inverter 810 due to excessive inrush current demands and seamlessly transfer the load to the ramping inverter 825 for controlled starting.

[0065] In various embodiments, the control system may implement automatic detection of loads demanding excessive inrush current. Upon detection of such conditions, the system may immediately reduce output voltage and frequency to reduce input current to the capacity of the power source. This response may be automatic and require no user input, providing a plug-and-play solution for managing high-inrush-current loads.

[0066] The system may implement automatic ramping of voltage and frequency in a prescribed ratio to limit input current to a user-settable value. The voltage and frequency ramp may be automatic and require no user input, with the ramp rate dynamically adjusted based on monitored current levels to ensure optimal performance while maintaining current limitations.

[0067] Various embodiments may implement an automatic internal bypass operation whereby the inverter synchronizes the output voltage waveform with the input voltage waveform and then automatically closes a bypass relay, removing the inverter from the circuit and suspending its operation. This bypass functionality may minimize heat generation within the system enclosure, enabling the use of passively cooled, hermetically sealed enclosures for enhanced robustness and universal applicability.

[0068] The systems described herein may be configured as single-phase consumer- oriented devices where the variable frequency drive functionality is pre-integrated and pre- configured for the application, requiring minimal user setup. This approach may eliminate the need for complex user interfaces or external control systems typically associated with industrial variable frequency drives, making the technology accessible for consumer-grade applications.

[0069] In some examples, the system architecture may include a rectifier having an input coupled to an AC voltage source and an output coupled to a unipolar voltage node, with an inverter having an input coupled to the unipolar voltage node and an output coupled to an inverter output node. A bypass switch may have an output node configured to connect to a load, a first bypass input configured to connect directly to the AC voltage source, and a second input configured to connect to the inverter output node. The controller may be configured to receive an input monitor signal representative of a phase of the AC voltage source and an output monitor signal representative of an output current supplied by the TPL Docket No.: 635-02-WO inverter to the load, and to generate an inverter control signal configured to cause the inverter to generate an output voltage waveform substantially in phase with the input monitor signal. In a first mode, the bypass switch may connect the second input to the bypass output node while the controller regulates the output current supplied to the load in response to the output monitor signal according to a predetermined voltage to frequency ratio, and in a second mode, the bypass switch may connect the first input to the bypass switch output node. When transitioning from the first mode to the second mode, the bypass switch may disconnect from the inverter output node before connecting directly to the AC voltage source, with the controller configured to transition from the first mode to the second mode in response to the phase error between the voltage waveform at the inverter output being within a predetermined margin of the phase of the AC input voltage source.

[0070] Although various embodiments have been described with reference to the figures, other embodiments are possible.

[0071] In some implementations, the controller 145 may include a bypass circuit (e.g., an analog circuit, a digital circuit) for continuous operation. For example, the AICPS 105 may include a bypass circuit that, once the VFACPS 100 reaches nominal frequency and voltage, the controller 145 may seamlessly be transferred to supply power to the loads 115 using the bypass circuit. For example, the bypass circuit may free up the inverter 135 (e.g., the VFD) to immediately support a startup of another load. Various embodiments may improve overall system efficiency (e.g., throughput).

[0072] In some implementations, the controller 145 may include an auto-detection of maximum allowable current engine. For example, the auto-detection of maximum allowable current engine may store (e.g., in a memory, in a datastore) a historically highest current level tolerated by the AICPS 105 and the limited AC power input 110. For example, the historically highest current level may be used as a pre-programmed current limit (e.g., by updating the user-selected CLS 155) for future operations. Various embodiments may offer a dynamically adaptable user-selected CLS 155.

[0073] In some implementations, the AICPS 105 may include a dedicated DC input. For example, the AICPS 105 may be connected to DC sources including solar battery systems. For example, the AICPS 105 connected to the DC sources may remove the requirement for an inverter 110.

[0074] In some implementations, the AICPS 105 may include a user-selectable partial speed run mode. For example, the user-selectable partial speed run mode may continue operation of some or all the loads 115 when the steady state current requirements at full TPL Docket No.: 635-02-WO nominal voltage and frequency exceed a maximum current capacity. In some examples, the user-selectable partial speed run mode may operate the loads 115 at a reduced speed that may still produce useful work. In some embodiments, the user-selectable partial speed run mode may include user-selected appliances (e.g., pumps and fans) to be operable.

[0075] Although an exemplary system has been described with reference to the figures, other implementations may be deployed in other industrial, scientific, medical, commercial, and / or residential applications.

[0076] In various embodiments, some bypass circuits implementations may be controlled in response to signals from analog or digital components, which may be discrete, integrated, or a combination of each. Some embodiments may include programmed, programmable devices, or some combination thereof (e.g., PLAs, PLDs, ASICs, microcontroller, microprocessor), and may include one or more data stores (e.g., cell, register, block, page) that provide single or multi-level digital data storage capability, and which may be volatile, non-volatile, or some combination thereof. Some control functions may be implemented in hardware, software, firmware, or a combination of any of them.

[0077] Computer program products may contain a set of instructions that, when executed by a processor device, cause the processor to perform prescribed functions. These functions may be performed in conjunction with controlled devices in operable communication with the processor. Computer program products, which may include software, may be stored in a data store tangibly embedded on a storage medium, such as an electronic, magnetic, or rotating storage device, and may be fixed or removable (e.g., hard disk, floppy disk, thumb drive, CD, DVD).

[0078] Although an example of a system, which may be portable, has been described with reference to the above figures, other implementations may be deployed in other processing applications, such as desktop and networked environments.

[0079] Temporary auxiliary energy inputs may be received, for example, from chargeable or single use batteries, which may enable use in portable or remote applications. Some embodiments may operate with other DC voltage sources, such as (nominal) batteries, for example. Alternating current (AC) inputs, which may be provided, for example from a 50 / 60 Hz power port, or from a portable electric generator, may be received via a rectifier and appropriate scaling. Provision for AC (e.g., sine wave, square wave, triangular wave) inputs may include a line frequency transformer to provide voltage step-up, voltage step- down, and / or isolation. TPL Docket No.: 635-02-WO

[0080] Although particular features of an architecture have been described, other features may be incorporated to improve performance. For example, caching (e.g., L1, L2, …) techniques may be used. Random access memory may be included, for example, to provide scratch pad memory and or to load executable code or parameter information stored for use during runtime operations. Other hardware and software may be provided to perform operations, such as network or other communications using one or more protocols, wireless (e.g., infrared) communications, stored operational energy and power supplies (e.g., batteries), switching and / or linear power supply circuits, software maintenance (e.g., self- test, upgrades), and the like. One or more communication interfaces may be provided in support of data storage and related operations.

[0081] Some systems may be implemented as a computer system that can be used with various implementations. For example, various implementations may include digital circuitry, analog circuitry, computer hardware, firmware, software, or combinations thereof. Apparatus can be implemented in a computer program product tangibly embodied in an information carrier, e.g., in a machine-readable storage device, for execution by a programmable processor; and methods can be performed by a programmable processor executing a program of instructions to perform functions of various embodiments by operating on input data and generating an output. Various embodiments can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and / or at least one output device. A computer program is a set of instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result. A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0082] Suitable processors for the execution of a program of instructions include, by way of example, both general and special purpose microprocessors, which may include a single processor or one of multiple processors of any kind of computer. Generally, a processor will receive instructions and data from a read-only memory or a random-access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memories for storing instructions and data. Generally, a computer will also include, or be operatively coupled to communicate with, one or more mass storage TPL Docket No.: 635-02-WO devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including, by way of example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits).

[0083] In some implementations, each system may be programmed with the same or similar information and / or initialized with substantially identical information stored in volatile and / or non-volatile memory. For example, one data interface may be configured to perform auto configuration, auto download, and / or auto update functions when coupled to an appropriate host device, such as a desktop computer or a server.

[0084] In some implementations, one or more user-interface features may be custom configured to perform specific functions. Various embodiments may be implemented in a computer system that includes a graphical user interface and / or an Internet browser. To provide for interaction with a user, some implementations may be implemented on a computer having a display device. The display device may, for example, include an LED (light-emitting diode) display. In some implementations, a display device may, for example, include a CRT (cathode ray tube). In some implementations, a display device may include, for example, an LCD (liquid crystal display). A display device (e.g., monitor) may, for example, be used for displaying information to the user. Some implementations may, for example, include a keyboard and / or pointing device (e.g., mouse, trackpad, trackball, joystick), such as by which the user can provide input to the computer.

[0085] In various implementations, the system may communicate using suitable communication methods, equipment, and techniques. For example, the system may communicate with compatible devices (e.g., devices capable of transferring data to and / or from the system) using point-to-point communication in which a message is transported directly from the source to the receiver over a dedicated physical link (e.g., fiber optic link, point-to-point wiring, daisy-chain). The components of the system may exchange information by any form or medium of analog or digital data communication, including packet-based messages on a communication network. Examples of communication networks include, e.g., a LAN (local area network), a WAN (wide area network), MAN (metropolitan area network), wireless and / or optical networks, the computers and networks TPL Docket No.: 635-02-WO forming the Internet, or some combination thereof. Other implementations may transport messages by broadcasting to all or substantially all devices that are coupled together by a communication network, for example, by using omni-directional radio frequency (RF) signals. Still other implementations may transport messages characterized by high directivity, such as RF signals transmitted using directional (i.e., narrow beam) antennas or infrared signals that may optionally be used with focusing optics. Still other implementations are possible using appropriate interfaces and protocols such as, by way of example and not intended to be limiting, USB 2.0, Firewire, ATA / IDE, RS-232, RS-422, RS-485, 802.11 a / b / g, Wi-Fi, Ethernet, IrDA, FDDI (fiber distributed data interface), token-ring networks, multiplexing techniques based on frequency, time, or code division, or some combination thereof. Some implementations may optionally incorporate features such as error checking and correction (ECC) for data integrity, or security measures, such as encryption (e.g., WEP) and password protection.

[0086] In various embodiments, the computer system may include Internet of Things (IoT) devices. IoT devices may include objects embedded with electronics, software, sensors, actuators, and network connectivity which enable these objects to collect and exchange data. IoT devices may be in-use with wired or wireless devices by sending data through an interface to another device. IoT devices may collect useful data and then autonomously flow the data between other devices.

[0087] Various examples of modules may be implemented using circuitry, including various electronic hardware. By way of example and not limitation, the hardware may include transistors, resistors, capacitors, switches, integrated circuits, other modules, or some combination thereof. In various examples, the modules may include analog logic, digital logic, discrete components, traces and / or memory circuits fabricated on a silicon substrate including various integrated circuits (e.g., FPGAs, ASICs), or some combination thereof. In some embodiments, the module(s) may involve execution of preprogrammed instructions, software executed by a processor, or some combination thereof. For example, various modules may involve both hardware and software.

[0088] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, advantageous results may be achieved if the steps of the disclosed techniques were performed in a different sequence, or if components of the disclosed systems were combined in a different manner, or if the components were supplemented with other components. Accordingly, other implementations are contemplated. TPL Docket No.: 635-02-WO

[0089] Clause 1. A starting circuit system comprising: a load; an AC source paired with the load; a rectifier having an input coupled to the AC source and an output coupled to a unipolar voltage node; an inverter having an input coupled to the unipolar voltage node and an output coupled to an inverter output node; a bypass switch having an output node configured to connect to the load, a first bypass input configured to connect to the AC source, and a second input configured to connect to the inverter output node; and a controller configured to: recognize when the load cannot be served by the paired AC source; start the load by controlling the inverter to generate an output voltage waveform and connecting the bypass switch to route power from the inverter to the load; and transfer control of the load back to the AC source by transitioning the bypass switch to connect the AC source directly to the load, wherein the controller is configured to receive an input monitor signal representative of a phase of the AC source and an output monitor signal representative of an output current supplied to the load, and to generate an inverter control signal configured to cause the inverter to generate the output voltage waveform substantially in phase with the input monitor signal, wherein, in a first mode, the bypass switch connects the second input to the bypass output node and the controller regulates the output current supplied to the load in response to the output monitor signal according to a predetermined voltage to frequency ratio, and in a second mode, the bypass switch connects the first input to the bypass switch output node, wherein, when transitioning from the first mode to the second mode, the bypass switch disconnects from the inverter output node before connecting directly to the AC source, and wherein the controller is configured to transition from the first mode to the second mode in response to predetermined conditions being met.

[0090] Clause 2. The starting circuit system of clause 1, wherein the controller is configured to increase the voltage and frequency of the inverter output waveform according to a predetermined voltage to frequency ratio.

[0091] Clause 3. The starting circuit system of clause 2, wherein the ramp rate of the voltage and frequency of the inverter output is dynamically controlled so as to prevent the input current from exceeding the capacity of the AC source.

[0092] Clause 4. The starting circuit system of clause 3, wherein the dynamically controlled ramp rate comprises a feedback-controlled rate that varies in response to the monitored output current to prevent exceeding the capacity of the AC source. TPL Docket No.: 635-02-WO

[0093] Clause 5. The starting circuit system of clause 1, wherein the controller is configured to monitor an input current drawn from the AC source and initiate the first mode when the input current exceeds a predetermined threshold value.

[0094] Clause 6. The starting circuit system of clause 1, wherein the controller is configured to synchronize the output voltage waveform with the AC source by matching both phase and frequency before transitioning from the first mode to the second mode.

[0095] Clause 7. The starting circuit system of clause 1, wherein the predetermined conditions comprise the output current reaching a predetermined threshold value.

[0096] Clause 8. The starting circuit system of clause 1, wherein the predetermined conditions comprise the inverter output waveform achieving synchronization with the AC source within a predetermined phase tolerance.

[0097] Clause 9. The starting circuit system of clause 1, wherein the controller is configured to monitor a voltage magnitude of the AC source and determine that the load cannot be served by the paired AC source when the voltage magnitude falls below a predetermined minimum threshold.

[0098] Clause 10. The starting circuit system of clause 1, wherein the bypass switch comprises a contactor assembly having a first contactor configured to selectively connect the first bypass input to the bypass output node and a second contactor configured to selectively connect the second input to the bypass output node.

[0099] Clause 11. A method of operating a starting circuit system, the method comprising: providing a load; providing an AC source paired with the load; providing a rectifier having an input coupled to the AC source and an output coupled to a unipolar voltage node; providing an inverter having an input coupled to the unipolar voltage node and an output coupled to an inverter output node; providing a bypass switch having an output node configured to connect to the load, a first bypass input configured to connect to the AC source, and a second input configured to connect to the inverter output node; and using a controller to: recognize when the load cannot be served by the paired AC source; start the load by controlling the inverter to generate an output voltage waveform and connecting the bypass switch to route power from the inverter to the load; and transfer control of the load back to the AC source by transitioning the bypass switch to connect the AC source directly to the load, wherein the controller receives an input monitor signal representative of a phase of the AC source and an output monitor signal representative of an output current supplied to the load, and generates an inverter control signal configured to cause the inverter to generate the output voltage waveform substantially in phase with the input monitor signal, TPL Docket No.: 635-02-WO wherein, in a first mode, the bypass switch connects the second input to the bypass output node and the controller regulates the output current supplied to the load in response to the output monitor signal according to a predetermined voltage to frequency ratio, and in a second mode, the bypass switch connects the first input to the bypass switch output node, wherein, when transitioning from the first mode to the second mode, the bypass switch disconnects from the inverter output node before connecting directly to the AC source, and wherein the controller transitions from the first mode to the second mode in response to predetermined conditions being met.

[0100] Clause 12. The method of clause 11, wherein the controller is configured to increase the voltage and frequency of the inverter output waveform according to a predetermined voltage to frequency ratio.

[0101] Clause 13. The method of clause 12, wherein the ramp rate of the voltage and frequency of the inverter output is dynamically controlled so as to prevent the input current from exceeding the capacity of the AC source.

[0102] Clause 14. The method of clause 13, wherein the dynamically controlled ramp rate comprises a feedback-controlled rate that varies in response to the monitored output current to prevent exceeding the capacity of the AC source.

[0103] Clause 15. The method of clause 11, wherein the controller is configured to monitor an input current drawn from the AC source and initiate the first mode when the input current exceeds a predetermined threshold value.

[0104] Clause 16. The method of clause 11, wherein the controller is configured to synchronize the output voltage waveform with the AC source by matching both phase and frequency before transitioning from the first mode to the second mode.

[0105] Clause 17. The method of clause 11, wherein the predetermined conditions comprise the output current reaching a predetermined threshold value.

[0106] Clause 18. The method of clause 11, wherein the predetermined conditions comprise the inverter output waveform achieving synchronization with the AC source within a predetermined phase tolerance.

[0107] Clause 19. The method of clause 11, wherein the controller monitors a voltage magnitude of the AC source and determines that the load cannot be served by the paired AC source when the voltage magnitude falls below a predetermined minimum threshold.

[0108] Clause 20. The method of clause 11, wherein the bypass switch comprises a contactor assembly having a first contactor configured to selectively connect the first TPL Docket No.: 635-02-WO bypass input to the bypass output node and a second contactor configured to selectively connect the second input to the bypass output node.

Claims

TPL Docket No.: 635-02-WO CLAIMS What is claimed is:

1. A starting circuit system comprising: a load; an AC source paired with the load; a rectifier having an input coupled to the AC source and an output coupled to a unipolar voltage node; an inverter having an input coupled to the unipolar voltage node and an output coupled to an inverter output node; a bypass switch having an output node configured to connect to the load, a first bypass input configured to connect to the AC source, and a second input configured to connect to the inverter output node; and a controller configured to: recognize when the load cannot be served by the paired AC source; start the load by controlling the inverter to generate an output voltage waveform and connecting the bypass switch to route power from the inverter to the load; and transfer control of the load back to the AC source by transitioning the bypass switch to connect the AC source directly to the load, wherein the controller is configured to receive an input monitor signal representative of a phase of the AC source and an output monitor signal representative of an output current supplied to the load, and to generate an inverter control signal configured to cause the inverter to generate the output voltage waveform substantially in phase with the input monitor signal, wherein, in a first mode, the bypass switch connects the second input to the bypass output node and the controller regulates the output current supplied to the load in response to the outputTPL Docket No.: 635-02-WO monitor signal according to a predetermined voltage to frequency ratio, and in a second mode, the bypass switch connects the first input to the bypass switch output node, wherein, when transitioning from the first mode to the second mode, the bypass switch disconnects from the inverter output node before connecting directly to the AC source, and wherein the controller is configured to transition from the first mode to the second mode in response to predetermined conditions being met.

2. The starting circuit system of claim 1, wherein the controller is configured to increase the voltage and frequency of the inverter output waveform according to a predetermined voltage to frequency ratio.

3. The starting circuit system of claim 2, wherein the ramp rate of the voltage and frequency of the inverter output is dynamically controlled so as to prevent the input current from exceeding the capacity of the AC source.

4. The starting circuit system of claim 3, wherein the dynamically controlled ramp rate comprises a feedback-controlled rate that varies in response to the monitored output current to prevent exceeding the capacity of the AC source.

5. The starting circuit system of claim 1, wherein the controller is configured to monitor an input current drawn from the AC source and initiate the first mode when the input current exceeds a predetermined threshold value.

6. The starting circuit system of claim 1, wherein the controller is configured to synchronize the output voltage waveform with the AC source by matching both phase and frequency before transitioning from the first mode to the second mode.

7. The starting circuit system of claim 1, wherein the predetermined conditions comprise the output current reaching a predetermined threshold value.TPL Docket No.: 635-02-WO 8. The starting circuit system of claim 1, wherein the predetermined conditions comprise the inverter output waveform achieving synchronization with the AC source within a predetermined phase tolerance.

9. The starting circuit system of claim 1, wherein the controller is configured to monitor a voltage magnitude of the AC source and determine that the load cannot be served by the paired AC source when the voltage magnitude falls below a predetermined minimum threshold.

10. The starting circuit system of claim 1, wherein the bypass switch comprises a contactor assembly having a first contactor configured to selectively connect the first bypass input to the bypass output node and a second contactor configured to selectively connect the second input to the bypass output node.

11. A method of operating a starting circuit system, the method comprising: providing a load; providing an AC source paired with the load; providing a rectifier having an input coupled to the AC source and an output coupled to a unipolar voltage node; providing an inverter having an input coupled to the unipolar voltage node and an output coupled to an inverter output node; providing a bypass switch having an output node configured to connect to the load, a first bypass input configured to connect to the AC source, and a second input configured to connect to the inverter output node; and using a controller to: recognize when the load cannot be served by the paired AC source;TPL Docket No.: 635-02-WO start the load by controlling the inverter to generate an output voltage waveform and connecting the bypass switch to route power from the inverter to the load; and transfer control of the load back to the AC source by transitioning the bypass switch to connect the AC source directly to the load, wherein the controller receives an input monitor signal representative of a phase of the AC source and an output monitor signal representative of an output current supplied to the load, and generates an inverter control signal configured to cause the inverter to generate the output voltage waveform substantially in phase with the input monitor signal, wherein, in a first mode, the bypass switch connects the second input to the bypass output node and the controller regulates the output current supplied to the load in response to the output monitor signal according to a predetermined voltage to frequency ratio, and in a second mode, the bypass switch connects the first input to the bypass switch output node, wherein, when transitioning from the first mode to the second mode, the bypass switch disconnects from the inverter output node before connecting directly to the AC source, and wherein the controller transitions from the first mode to the second mode in response to predetermined conditions being met.

12. The method of clause 11, wherein the controller is configured to increase the voltage and frequency of the inverter output waveform according to a predetermined voltage to frequency ratio.

13. The method of claim 12, wherein the ramp rate of the voltage and frequency of the inverter output is dynamically controlled so as to prevent the input current from exceeding the capacity of the AC source.TPL Docket No.: 635-02-WO 14. The method of claim 13, wherein the dynamically controlled ramp rate comprises a feedback-controlled rate that varies in response to the monitored output current to prevent exceeding the capacity of the AC source.

15. The method of claim 11, wherein the controller is configured to monitor an input current drawn from the AC source and initiate the first mode when the input current exceeds a predetermined threshold value.

16. The method of claim 11, wherein the controller is configured to synchronize the output voltage waveform with the AC source by matching both phase and frequency before transitioning from the first mode to the second mode.

17. The method of clause 11, wherein the predetermined conditions comprise the output current reaching a predetermined threshold value.

18. The method of clause 11, wherein the predetermined conditions comprise the inverter output waveform achieving synchronization with the AC source within a predetermined phase tolerance.

19. The method of clause 11, wherein the controller monitors a voltage magnitude of the AC source and determines that the load cannot be served by the paired AC source when the voltage magnitude falls below a predetermined minimum threshold.

20. The method of clause 11, wherein the bypass switch comprises a contactor assembly having a first contactor configured to selectively connect the first bypass input to the bypass output node and a second contactor configured to selectively connect the second input to the bypass output node.

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