Abstract: A method is disclosed for reducing an influence of voltage ripple on battery test measurements of battery cells coupled in series that form a direct current (DC) bus. A calibration operation is used to obtain a ratiometric difference between first and second series connected battery cells of the DC bus, which is indicative of a variance in their respective output voltages. Voltage measurements across each of the two cells may then be obtained at least substantially simultaneously. The ratiometric difference may be used to modify the voltage measurement taken across the second cell to produce a modified voltage measurement of the second cell. A difference between the measured voltage across the first battery cell and the modified voltage measurement may then be determined, which represents a filtered DC test voltage that has substantially all of the voltage ripple removed therefrom.

Abstract: A repetitive servomechanism controller for a UPS system has an inner control loop and an outer control loop. The inner control loop regulates inverter current and the outer control loop regulates inverter voltage. The outer control loop includes a repetitive controller in combination with a harmonic servomechanism controller and a feed-forward controller.

Abstract: A cooling system for transferring heat from a heat load to an environment has a volatile working fluid. The cooling system includes first and second cooling cycles that are thermally connected to the first cooling cycle. The first cooling cycle is not a vapor compression cycle and includes a pump, an air-to-fluid heat exchanger, and a fluid-to-fluid heat exchanger. The second cooling cycle can include a chilled water system for transferring heat from the fluid-to-fluid heat exchanger to the environment. Alternatively, the second cooling cycle can include a vapor compression system for transferring heat from the fluid-to-fluid heat exchanger to the environment.

Abstract: A cooling system for transferring heat from a heat load to an environment has a volatile working fluid. The cooling system includes first and second cooling cycles that are thermally connected to the first cooling cycle. The first cooling cycle is not a vapor compression cycle and includes a pump, an air-to-fluid heat exchanger, and a fluid-to-fluid heat exchanger. The second cooling cycle can include a chilled water system for transferring heat from the fluid-to-fluid heat exchanger to the environment. Alternatively, the second cooling cycle can include a vapor compression system for transferring heat from the fluid-to-fluid heat exchanger to the environment.

Abstract: An UPS system and a method of supplying power to a non-linear load are provided. The UPS system may include a bypass module configured to supply a fundamental wave current to a non-linear load of the UPS system; and a power module configured to supply a harmonic current to the non-linear load when the bypass module operates normally.

Abstract: A cooling system includes a cooling circuit having an evaporator, a condenser, a compressor, an expansion device, a liquid pump, and a receiver/surge tank coupled between the condenser and the liquid pump. The cooling system has a direct expansion mode and a pumped refrigerant economizer mode. When the cooling system switches from the direct expansion mode to the pumped refrigerant economizer mode, refrigerant is flushed from the refrigerant/surge tank so that the cooling circuit is overcharged when it begins operating in the pumped refrigerant economizer mode.

Abstract: A common mode choke in a 3-wire transformer free UPS system with which different rectifier and bypass power sources are used is eliminated by using different types of PWM control depending on whether the inverter is paralleled with the bypass power source. When the inverter is paralleled with the bypass power source, a type of PWM control is used that does not have common mode voltage injection. When the inverter is not paralleled with the bypass power source, a type of PWM control is used that has common mode voltage injection. In an aspect, the PWM control that does not have common mode voltage injection is sine-triangle PWM and the PWM control that has common mode voltage injection is space-vector PWM.

Abstract: A cooling system has a cabinet and a plurality of separate cooling stages including an upstream cooling stage and a downstream cooling stage. At least the upstream cooling state is a variable capacity cooling stage. Each cooling stage has a cooling circuit. Evaporators of the cooling circuits are arranged in the cabinet so that air passes over them in serial fashion. A controller when a Call for Cooling first reaches a point where cooling is needed, operating the upstream cooling circuit to provide cooling and not the downstream cooling circuit. When the Call for Cooling has increased to a second point, the controller additionally operates the downstream cooling circuit to provide cooling. The cooling capacity at which the upstream cooling circuit is being operated is less than its full capacity when the Call for Cooling reaches the second point.

Abstract: A method of retrofitting a computer room air conditioner having a direct expansion refrigeration circuit to increase a maximum temperature delta of the computer room air conditioner includes adding an upstream cooling circuit that is a pumped refrigerant cooling circuit having a cooling coil disposed upstream of a cooling coil of the direct expansion refrigeration circuit. Air to be cooled is passed in serial fashion across the cooling coil of the upstream cooling circuit and then the cooling coil of the direct expansion refrigeration circuit. The upstream cooling circuit is controlled to cool the air flowing across the cooling coil of the upstream cooling circuit to provide only sensible cooling and so that a temperature of the upstream cooling coil is always above a dewpoint of the air flowing across the upstream cooling coil. The direction direct expansion refrigeration circuit is controlled to provide any latent cooling that is needed.

Abstract: A battery cell terminal quick connect clamp for attaching to a battery cell terminal has a conductive contact coupled to a connecting element to which a connector attached to the end of a battery monitoring lead can attach. The quick connect clamp includes a clamping mechanism that when in a clamped position presses the conductive contact against a side of the battery cell terminal.

Abstract: A repetitive servomechanism controller for a UPS system has an inner control loop and an outer control loop. The inner control loop regulates inverter current and the outer control loop regulates inverter voltage. The outer control loop includes a repetitive controller in combination with a harmonic servomechanism controller and a feed-forward controller.

Abstract: A client connection device for a UPS system includes a frame on which a main input distribution unit, a bypass input distribution unit, a battery distribution unit, and an output distribution unit are provided, in which the main input distribution unit and the bypass input distribution unit are arranged on the frame with being opposite to each other up and down, the output distribution unit and the battery distribution unit are arranged on the frame on different sides of the main input distribution unit and the bypass input distribution unit, and the battery distribution unit is side placed near the main input distribution unit and the bypass input distribution unit. A client connection device for a UPS system is provided which can be of a compact structure, be space saving, and be convenient for space operation.

Abstract: A cooling system has a cabinet and a plurality of separate cooling stages including an upstream cooling stage and a downstream cooling stage. At least the upstream cooling state is a variable capacity cooling stage. Each cooling stage has a cooling circuit. Evaporators of the cooling circuits are arranged in the cabinet so that air passes over them in serial fashion. A controller when a Call for Cooling first reaches a point where cooling is needed, operating the upstream cooling circuit to provide cooling and not the downstream cooling circuit. When the Call for Cooling has increased to a second point, the controller additionally operates the downstream cooling circuit to provide cooling. The cooling capacity at which the upstream cooling circuit is being operated is less than its full capacity when the Call for Cooling reaches the second point.

Abstract: A multiple uninterruptible power supply system includes at least two uninterruptible power supply modules. Each uninterruptible power supply module has a control unit with the control unit coupled to a synchronization bus. The uninterruptible power supply module are synchronized to each other with one of the uninterruptible power supply modules being operated as a sync master UPS and its control unit sending synchronization signals on the synchronization bus that are received on the synchronization bus by control units of each of the other uninterruptible power supply module which are each operated as a slave UPS synchronized to the sync master UPS. When a bypass power source for the uninterruptible power supply module that is being operated as the sync master becomes unqualified, another one of the UPS modules is operated as the sync master and its control unit then sends out the synchronization signals.

Abstract: An uninterruptible power supply includes a rectifier coupled to an input of an uninterruptible power supply and converts a first alternating current having a first alternating current voltage to a direct current. An inverter is coupled to an output of the uninterruptible power supply and converts the direct current to a second alternating current having a second alternating current voltage. A bypass switch bypasses the rectifier and the inverter and provides a bypass power from the input to the output when in a bypass state. A control module switches the bypass switch to the bypass state when in a bypass mode and switches the bypass switch to a non-bypass state when in a UPS mode. The control module adjusts the second alternating current voltage between first and second voltage levels when in an adaptive voltage control mode after switching from the bypass mode to the UPS mode.

Abstract: A system including a setpoint module, a summer, a control module, and an expansion valve module. The setpoint module is configured to indirectly control sub-cooling of a condenser by adjusting a superheat setpoint based on (i) a return air temperature setpoint or a supply air temperature setpoint, and (ii) an outdoor ambient temperature. The summer is configured to determine an error between the superheat setpoint and a superheat level of a compressor. The control module is configured to generate a control signal based on the error. The expansion valve module is configured to electronically control a state of an expansion valve based on the control signal.

Abstract: A battery monitor determines an internal resistance of a battery cell of a battery having parallel connected battery strings which accounts for errors introduced by the parallel connected battery strings. When determining the internal resistance of a battery cell, the battery monitor determines a baseline intercell resistance of an intercell connecting the negative terminal of the battery cell to the positive terminal of an adjacent battery. The battery monitor then applies a momentary load across the battery cell and immediately prior to releasing the load, measures the voltage across the battery cell (loaded voltage) and the voltage across the intercell. The battery monitor then calculates the current flowing through the intercell (intercell current) by dividing the measured voltage across the intercell by the determined intercell resistance.

Abstract: An inverter may include an inversion unit for converting a direct current bus voltage into an alternating current voltage, a first snubber unit, and a second snubber unit. The inversion unit may include a first external switch, a first internal switch, a second internal switch, and a second external switch which are connected in series in order between a direct current bus positive voltage terminal and a direct current bus negative voltage terminal. The first snubber unit may be connected between the direct current bus negative voltage terminal and the first internal switch for suppressing voltage stress of the first internal switch. The second snubber unit may be connected between the direct current bus positive voltage terminal and the second internal switch for suppressing voltage stress of the second internal switch.

Abstract: A cooling system has a tandem compressor, a condenser, an electronic expansion valve and an evaporator arranged in a direct expansion cooling circuit. The tandem compressor includes a variable capacity compressor and a fixed capacity compressor. A controller controls the electronic expansion valve and selects which of a plurality of superheat control modes to use in operating the electronic expansion valve based on control parameters and a current operating status of each of the variable capacity compressor and fixed capacity compressor of the tandem compressor.

Abstract: A method is disclosed for analyzing performance of a chilled water (CW) system having a plurality of CW components. The method may consider a collection of at least one of allowable operating points, allowable operating ranges or allowable operating conditions, for each one of the CW components. A user set or system measured ambient wet bulb (WB) temperature may be considered for an environment in which at least a subplurality of the CW components are located. Equivalent loop conditions may be calculated for each of the CW components covering a load being thermally managed by the CW system. For each one of the calculated equivalent loop conditions, a processor may generate information for balancing the CW components to meet load requirements, and then analyze and select a balance condition that yields the user preferable optimization.