摘要:
A variable speed drive is provided having a converter to convert an AC voltage to a DC voltage, a DC link to filter and store energy from the converter, and a plurality of inverters. Each inverter is configured to convert a DC voltage to an AC voltage and is electrically connected in parallel to the DC link. An interleaved pulse width modulation control technique is used to control the operation of the plurality of inverters and possibly the converter to lower the RMS ripple current in the DC link.
摘要:
A variable speed drive with a converter that is controllable to precharge a DC link is provided. The variable speed drive also includes an inverter. The converter converts a fixed line frequency, fixed line voltage AC power from an AC power source into DC power. The DC link filters the DC power from the converter. Finally, the inverter is connected in parallel with the DC link and converts the DC power from the DC link into a variable frequency, variable voltage AC power. The converter includes a plurality of pairs of power switches, wherein each pair of power switches includes a reverse blocking power switch connected in anti-parallel to another reverse blocking power switch. Alternatively, each pair of power switches includes a reverse blocking power switch connected in anti-parallel with a silicon carbide controlled rectifier.
摘要:
A chiller system includes a switched reluctance motor for powering the compressor of the chiller system. A variable speed drive with a boost converter provides a boosted voltage to the switched reluctance motor. The switched reluctance motor and the compressor may be disposed within the same hermetic enclosure and driven by a common drive shaft. Cooling for both the variable speed drive and the switched reluctance motor is provided from condenser water in the condenser water circuit, or from an intermediate liquid cooled by water from the condenser circuit to increase system efficiency. Windage losses are reduced by barriers introduced within the motor, and by maintaining a reduced pressure in the switched reluctance motor.
摘要:
A variable speed drive with a boost converter is provided for a chiller system driven by an induction motor. The boost converter can be a diode or thyristor rectifier followed by a boost DC/DC converter or a three-phase pulse width modulated boost converter. The boost converter provides a boosted voltage to the DC link, which results in a boosted voltage being applied to the induction motor by the inverter of the variable speed drive.
摘要:
A variable speed drive with a boost converter is provided for a chiller system driven by a switched reluctance motor. The boost converter can be a diode or thyristor rectifier followed by a boost DC/DC converter or a three-phase pulse width modulated boost converter. The boost converter provides a boosted voltage to the DC link, which results in a boosted voltage being applied to the switched reluctance motor by the inverter of the variable speed drive.
摘要:
A method of providing ride-through capability in a chiller/refrigeration system employs a variable speed drive with an active converter stage, a DC link stage and an inverter stage for providing variable frequency and voltage to power at least one motor. An induction motor is coupled to the output of the inverter stage for driving a compressor in the chiller/refrigeration system. The ride-through method comprises operating the active converter to regulate the DC link voltage of the DC link stage to a predetermined voltage level until the current through the active converter equals a predetermined current limit, then transferring regulation of the DC link to the inverter upon reaching the current limit of the converter. The compressor is unloaded, and the power flow through the inverter is reversed to maintain the voltage level of the DC link stage.
摘要:
A system is provided for attenuating tonal acoustic noise associated with a single positive displacement compressor, or multiple positive displacement compressors proximately located from each other. A controller selectably controls the rotational speed and the frequency of operation of each of the compressors. The controller controls the rotational speed of the compressors about a predetermined rotational speed, in a random manner, within the pre-selected speed band to reduce the magnitude of the central tonal acoustic frequency of the pressure pulsations and disperse the sound power over a wider acoustic bandwidth.
摘要:
A system for cancelling or attenuating noise in at least two positive displacement compressors proximately located from each other for use with a heating or cooling system. A lead compressor and a lag compressor have a controllable rotational speed and phase of operation. A controller selectably controls the rotational speed and the phase of operation of each of the compressors. The controller controls the rotational speed of the compressors at substantially the same speed for each compressor, with a phase-lock loop and a comparator circuit for each compressor. The controller controls the phase of operation of the compressors through an oscillator so that the lead and lag compressor pressure pulses are spaced between successive outlet pressure pulses to effectively double the combined pulsation frequency for noise attenuation.
摘要:
A system for cancelling or attenuating noise in at least two positive displacement compressors proximately located from each other for use with a heating or cooling system. A lead compressor and a lag compressor have a controllable rotational speed and phase of operation. A controller selectably controls the rotational speed and the phase of operation of each of the compressors. The controller controls the rotational speed of the compressors at substantially the same speed for each compressor, with a phase-lock loop and a comparator circuit for each compressor. The controller controls the phase of operation of the compressors through an oscillator so that the lead and lag compressor pressure pulses are spaced between successive outlet pressure pulses to effectively double the combined pulsation frequency for noise attenuation.
摘要:
A chiller system includes a refrigerant loop, the refrigerant loop further including a compressor, an air-cooled condenser arrangement and an evaporator arrangement connected in a first closed refrigerant loop. A motor is connected to the compressor to drive the compressor, a drive is connected to the motor to power the motor and a power/control panel controls the refrigerant loop. The power/control panel and the condenser arrangement are connected in a second closed coolant loop. The second closed coolant loop provides cooling to the enclosure and/or components within the enclosure disposed on a chill plate. Condensation is substantially prevented from forming inside the enclosure, despite the enclosure lacking a humidity control device.