Abstract: A method and an apparatus for transmitting and receiving data in a filter bank based multicarrier communication system are provided. The method includes receiving a plurality of data blocks and performing an Inverse Fast Fourier Transform (IFFT) operation on the plurality of data blocks, multiplying the plurality of data blocks on which IFFT has been performed and time axis filter coefficients, and transmitting a result obtained by adding the plurality of multiplied data blocks as a multi carrier signal.

Abstract: A method and an apparatus for transmitting and receiving data in a filter bank based multicarrier communication system are provided. The method includes receiving a plurality of data blocks and performing an Inverse Fast Fourier Transform (IFFT) operation on the plurality of data blocks, multiplying the plurality of data blocks on which IFFT has been performed and time axis filter coefficients, and transmitting a result obtained by adding the plurality of multiplied data blocks as a multi carrier signal.

Abstract: The invention relates to a reverse rotation preventing structure of a centrifugal compressor. The reverse rotation preventing structure of the centrifugal compressor comprises: a discharge pipeline of the centrifugal compressor; a suction pipeline of the centrifugal compressor; a bypass pipeline for connecting the discharge pipeline and the suction pipeline, wherein a predetermined valve is formed thereon; a control means for controlling an operation of the centrifugal compressor; and a detecting means for generating a predetermined signal to the control means if the operation of the centrifugal compressor is suddenly stopped, thereby opening the bypass pipeline.

Abstract: A system for cooling a turbo compressor includes two compressing parts on opposite ends of a rotational shaft driven by a motor. Fluid from a fluid chamber within the casing of the device is supplied to a bearing chamber when the temperature of the bearing chamber increases. A supply passage is formed in a first support where the radial bearing for supporting a load in the axial direction is formed. The open-and-shut valve supplies fluid when the temperature of the bearing chamber increases.

Abstract: A turbo compressor is provided which includes a motor having a stator with a rotor which rotates in the inside of the stator. A rotation shaft is press-fitted into the rotor and is integrally rotated with the rotor. A bearing is provided for supporting the rotation shaft of the motor. At least one impeller is attached to the rotation shaft of the motor and rotated therewith. A foil bearing including a plurality of foils is provided. First ends of the foils are respectively fitted into a multitude of engaging grooves defined on a circumferential inner surface of the stator, and second ends of the foils make contact with a circumferential outer surface of the rotor.

Abstract: A cooling system, which includes a compressor for compressing the refrigerant by operation of a motor, a condenser, an expansion means, and an evaporator, comprises a motor cooling device for cooling down the motor by making some of the refrigerant passed the condenser flow to the compressor according to temperature of the motor, and therefore the heat of high temperature generated from the motor in the compressor during the operation of the compressor which is used in the cooling system can be cooled down efficiently.

Abstract: The invention relates to a reverse rotation preventing structure of a centrifugal compressor. The reverse rotation preventing structure of the centrifugal compressor comprises: a discharge pipeline of the centrifugal compressor; a suction pipeline of the centrifugal compressor; a bypass pipeline for connecting the discharge pipeline and the suction pipeline, wherein a predetermined valve is formed thereon; a control means for controlling an operation of the centrifugal compressor; and a detecting means for generating a predetermined signal to the control means if the operation of the centrifugal compressor is suddenly stopped, thereby opening the bypass pipeline.

Abstract: A cooling system, which includes a compressor for compressing the refrigerant by operation of a motor, a condenser, an expansion means, and an evaporator, comprises a motor cooling device for cooling down the motor by making some of the refrigerant passed the condenser flow to the compressor according to temperature of the motor, and therefore the heat of high temperature generated from the motor in the compressor during the operation of the compressor which is used in the cooling system can be cooled down efficiently.

Abstract: A turbo compressor includes: a casing having a fluid chamber for receiving a fluid from an external source; a driving unit disposed in the casing and generating a rotational force; a first compressing part installed at one side of a rotational shaft rotated according to the driving of the driving unit and first compressing the fluid; a second compressing part installed at the other side of the rotational shaft and secondly compressing the fluid compressed in the first compressing part; and a bearing cooling unit for supplying a fluid of the fluid chamber to a bearing chamber to perform a cooling operation when a temperature of the bearing chamber where the thrust bearing for supporting a load working in an axial direction of the rotational shaft is mounted is increased, and cutting off the fluid from being introduced into the bearing chamber when the temperature of the bearing chamber is maintained at a proper level.

Abstract: A centrifugal compressor includes first and second impellers coupled to opposite ends of a drive shaft. Each impeller includes a hub with a plurality of blades on a front face. The blades compress a fluid, while forcing the fluid off an outer periphery of the hub. At least one of the impellers includes a plurality of uniformly shaped pressure attenuating grooves provided around its outer periphery. The pressure attenuating grooves reduce an axial load applied to the impeller, and act to balance the overall resultant axial load applied to the drive shaft by the two impellers, thereby reducing wear on thrust bearings engaging the rotating drive shaft.

Abstract: The present invention relates to a turbo compressor which is capable of minimizing deformation of construction parts which may occur in welding or after welding and simplifying the manufacture and assembly by forming the outer diameter of a driving shaft so as to be stepped and joining the construction parts with bolts and pins.

Abstract: Disclosed is a turbo compressor. The turbo compressor comprising a motor having a stator with a rotor which rotates in the inside of the stator and a rotation shaft which is press-fitted into the rotor and integrally rotated with the rotor, a bearing means for supporting the rotation shaft of the motor, at least one impeller attached to the rotation shaft of the motor and rotated therewith and a foil bearing including a plurality of foils which one ends thereof are respectively fitted into a multitude of engaging grooves defied on a circumferential inner surface of the stator, and the other ends thereof make contact with a circumferential outer surface of the rotor.

Abstract: The present invention relates to a turbo compressor which is capable of minimizing deformation of construction parts occurred in welding or after welding and simplifying manufacture and assembly by forming the outer diameter of a driving shaft so as to be stepped and combining the construction parts with bolts and pins.

Abstract: Disclosed is a centrifugal compressor structure including impellers, each of the impellers including a hub coupled to a drive shaft, a plurality of blades provided at a front surface of the hub and adapted to compress an external fluid while forcing the fluid to flow from an upstream end of the hub to a downstream end of the hub, and a plurality of uniformly-shaped pressure attenuating grooves provided at an outer peripheral edge of the hub and adapted to reduce an axial load applied to the impeller. The formation of the pressure attenuating grooves are carried out without any variation in the size and length of each blade serving as important factors for adjusting the fluid compression degree of the impeller, so that thrust bearings adapted to support an axial load are effectively protected, thereby eliminating problems resulting from the thrust bearings.

Abstract: A turbo compressor is disclosed. The compressor includes a hermetically sealed shell, a motor chamber formed at a center portion of the shell, a driving motor installed in the motor chamber, a driving shaft engaged with the driving motor having its one end inserted into a first compression chamber and its other end inserted into a second compression chamber with said first and second compression chambers being formed at both sides of the shell, first and second impellers disposed in the first and second compression chambers in a face-to-face form and rotatably engaged with both ends of the driving shaft, and a gas flow path through which a refrigerant gas is sucked for thereby first compressing the gas in the first compression chamber and discharging to the second compression chamber for thereby implementing a small size compressor, decreasing the number of parts and increasing a compression efficiency.

Abstract: A motor cooling structure for a turbo compressor is disclosed. The structure includes a refrigerant suction tube communicating with one lateral wall of the sealed container and extended from the evaporator, a first refrigerant flow tube communicating with another lateral wall of the sealed container, with the first refrigerant flow tube communicating with the first compression chamber, a second refrigerant flow tube through which the first compression chamber communicates with the second compression chamber, and a refrigerant discharge tube communicating with the second compression chamber communicating with a condenser, for thereby enhancing a cooling efficiency of the driving motor by directly introducing a low temperature refrigerant from an evaporator into a motor chamber.