A plurality of scroll compressors with different fixed volume indexes are connected in fluid parallel circuit and configured to selectively operate to maximize isentropic efficiency at different condensing temperatures. Different quantities of scroll compressors of different volume indexes may be selected based upon typical climate or geographic location environmental conditions to attempt to maximize efficiency. A controller may selectively operate different combinations of the compressors of different volume indexes bases up load demands and condensing temperature conditions, which may be determined in a variety of ways.

In a motor driving apparatus having an inverter which can drive n (n being an integer not smaller than 2) motors each having a permanent magnet in its rotor, and a connection switching device for switching the connection state of the n motors, the connection switching device is operated to change the number of the motors connected to the inverter thereby to change the impedance as seen from the inverter towards the motors. When i (i being any of 2 to n) motors among the n motors are concurrently driven by the inverter, the voltage outputted by the inverter may be controlled such that the inductance values of the i motors are identical. It is possible to prevent hunting and step-out due to the phase difference between the motors driven by the inverter.

A rotor for an interior permanent magnet motor, an interior permanent magnet motor, and a compressor includes a rotor core, a plurality of U-shaped permanent magnet accommodating grooves, a plurality of first air grooves, and a plurality of first recesses, wherein the plurality of U-shaped permanent magnet accommodating grooves are arranged inside the rotor core at intervals; the plurality of first air grooves are provided outside the ends of the U-shaped permanent magnet accommodating grooves; and each first air groove is located on an extension line of the end of the corresponding U-shaped permanent magnet accommodating groove and is close to the outer contour of the rotor so as to form a plurality of first magnetic isolation bridges. Each first recess is recessed from the outer contour of the rotor towards the center of the rotor, starts from the end of the corresponding first magnetic isolation bridge at the outermost side of the rotor, and at most, extends to the first intersection point of the connecting line between the bottom center of the U-shaped permanent magnet accommodating groove and the center of the rotor, and the outer contour of the rotor, such that the air gap magnetic density generated between the outer contour of the rotor and the inner contour of a stator of the interior permanent magnet motor approaches a sine curve.

A compressor includes a shaft that is arranged along a rotation axis, a compression unit that drives along with rotation of the shaft, a rotor core that is fixed to the shaft, a plurality of permanent magnets that are embedded inside the rotor core, and a stator that causes the rotor core to rotate about the rotation axis, wherein a plurality of eccentric holes for adjusting balance when the shaft rotates are formed in the rotor core, and the plurality of eccentric holes are formed on an inner side of the polygonal region for which midpoints of sides at a side of the rotation axis among sides formed by side surfaces of the plurality of permanent magnet in a cross section perpendicular to the rotation axis serve as vertices.

An electric motor system is described. The electric motor system includes a drive circuit including an inverter configured to supply variable frequency current and a contactor configured to supply line frequency current. The electric motor system also includes an electric motor coupled to the drive circuit wherein the electric motor is communicatively coupled to a controller. The controller is configured to control the inverter to supply variable frequency current to the electric motor, thereby operating the electric motor at a motor speed, and determine, based upon at least one input parameter, a maximum potential motor speed the inverter can achieve. The controller is also configured to receive a command to operate the electric motor at line frequency current and control the drive circuit to transition from supplying variable frequency current to supplying line frequency current before the maximum potential motor speed the inverter can achieve is reached.

PROBLEM TO BE SOLVED To improve controllability of a motor including a stator with two-split structure.

SOLUTION
A motor 400 includes a stator 460 disposed to surround an outer circumference of a rotor 440 which rotates integrally with a drive shaft 420. The stator 460 includes an inner core 462 having multiple protrusions 462B radially outwardly extending from an outer circumferential surface of a cylindrical portion 462A, and a cylindrical outer core 464 having its inner circumferential surface side attached to a top of the protrusion 462B. A connection portion (first connection portion 462F) as a part for connecting a side surface (first side surface 462D) of the protrusion 462B at an upstream side in a rotating direction of the rotor 440 and an outer circumferential surface of the cylindrical portion 462A has a rounded shape. A connection portion (second connection portion 462G) as a part for connecting a side surface (second side surface 462E) of the protrusion 462B at a downstream side in the rotating direction of the rotor 440 and the outer circumferential surface of the cylindrical portion 462A has a rounded shape. A radius r1 of the rounded shape of the first connection portion 462F is greater than a radius r2 of the rounded shape of the second connection portion 462G.

In an air conditioner that uses a refrigerant mixture containing at least 1,2-difluoroethylene, high efficiency is achieved. In the air conditioner (1), a compressor (100, 200) can be driven without interposing a power conversion device between an AC power source (90, 190) and a motor (70, 170). Thus, it is possible to provide the air conditioner (1) that is environmentally friendly and has a relatively inexpensive configuration.

A power conversion apparatus includes a converter circuit converting alternating current voltage output from an AC power supply into direct current voltage. The converter circuit includes unit converters. The power conversion apparatus generates a reference duty based on detection values of a current detector and a voltage detector, and generates a pulse width modulation signal based on a result of comparison between a carrier signal and a corrected duty obtained by correcting the reference duty. When a first reference duty in a first carrier period differs from a second reference duty in a second carrier period subsequent to the first carrier period, a first corrected duty of a first phase in a first carrier period in one power supply period after and a second corrected duty of a second phase in the first carrier period in one power supply period after are controlled to have different values.

An air conditioning pack of a cooling system includes an air cycle machine assembly, a cabin air compressor assembly, and a mixing duct. The air cycle machine assembly includes a compressor configured to receive an air stream that includes bleed air to generate a compressed air stream. The air cycle machine assembly utilizes a first portion of the compressed air stream to power the compressor. The cabin air compressor assembly receives a second portion of the compressed air stream, and utilizes the second portion to generate compressed ram air. The mixing duct receives the compressed ram air and allows the compressed ram air to mix with one or more of the air stream upstream of the compressor or the compressed air stream downstream of the compressor to generate a hybrid air stream that is used for cooling at least a portion of a vehicle.

An electric compressor includes a compression portion, an electric motor, a drive circuit that has a circuit board on which electronic components are mounted, a housing, and a resin member. At least one of the electronic components is held by the resin member with the resin member sandwiched between the at least one of the electronic component and the circuit board. The electronic compressor includes a first metal member that is in contact with the at least one of the electronic components, and thermally connected to the housing, a second metal member that is disposed in the resin member, and a bolt by which the first metal member and the second metal member are fastened with each other.