A rotary-machine control device includes: a connection switching device switching a connection state of stator windings of a rotary machine; a current detection unit detecting a rotary machine current flowing in the rotary machine; a voltage application unit applying voltage to the rotary machine; a control unit generating a voltage command provided to the voltage application unit and outputting a switching command to switch the connection state to the connection switching device; and an open-phase determination unit determining presence or absence of disconnection in the rotary machine or presence or absence of disconnection of a power distribution line to the rotary machine. During rotation of the rotary machine, the control unit outputs the switching command and the open-phase determination unit determines presence or absence of disconnection.

The integrated expander and motor-compressor assembly comprises a compression section mounted between the two radial bearings on a trans-mission shaft, an expander cantilevered at a free end of the transmission shaft, a gas diffuser and a duct between the expander and a first radial bearing, the first radial bearing been the closest radial bearing to the expander. The gas diffuser diffuses a gas barrier which is sucked up by the duct.

Refrigerant compressor with a hermetically sealed housing and a drive unit in the interior of the housing. At least one damping element is in the housing is connected to the drive unit. The damping element has three contact areas separated from each other by an edge, in which in a first deflected state of the drive unit a first contact area contacts a first inner surface area of the housing, wherein in a second deflected state a second contact area contacts a second inner surface area of the housing, but the first contact area does not contact the first inner surface area, wherein in a third deflected state of the drive unit a third contact area contacts a third inner surface area, but the first and second contact areas do not contact the first and second inner surface areas, respectively.

A heat transfer unit includes: an electrical component casing defining an internal space, the internal space housing a transformer together with a control board and a power supply board; and a cooling unit which cools an electronic component on the power supply board during operation of a compressor.

A heat transfer unit includes: an electrical component casing defining an internal space, the internal space housing a transformer together with a control board and a power supply board; and a cooling unit which cools an electronic component on the power supply board during operation of a compressor.

An inverter for driving a motor that has a switchable connection of windings and drives a load element having a periodically varying load torque is provided. The inverter is controlled so that an output torque of the motor follows the periodic variation of the load torque. The inverter is controlled so that a current flowing through the motor is zero during a period including a minimum torque phase at which the load torque is at or near a minimum value. The connection is switched while the current flowing through the motor is zero. It is possible to switch the connection of the windings while the motor is rotating, and avoid an increase in apparatus size.

A core includes a laminated body. The laminated body includes a plurality of electrical steel sheets stacked one on another. The laminated body includes a contact area between a pair of adjacent electrical steel sheets of the plurality of electrical steel sheets. The contact area includes a first friction area and a second friction area with friction coefficients different from each other.

A motor apparatus includes a casing, a stator disposed in the casing, a rotor disposed on an inner circumference of the stator, a shaft disposed on an inner circumference of the rotor, a functional part disposed on an outer circumference of a first member, and a heat-resistant part disposed between the functional part and a second member. The first member is the stator or the shaft. The second member is the casing or the rotor.

A motor apparatus includes a casing, a stator disposed in the casing, a rotor disposed on an inner circumference of the stator, a shaft disposed on an inner circumference of the rotor, a functional part disposed on an outer circumference of a first member, and a heat-resistant part disposed between the functional part and a second member. The first member is the stator or the shaft. The second member is the casing or the rotor.

Lubricating oil has a kinematic viscosity in a range of 1 mm.sup.2/S to 7 mm.sup.2/S at 40° C., has a mass average molecular weight in a range of 150 to 400, and contains 0.5% by mass or more of a high molecular weight component. The high molecular weight component has a mass molecular weight of greater than or equal to 500. A crankshaft serving as a shaft part of a compression element includes a main shaft that includes a sliding surface. In a case where the sliding surface is a single sliding surface, a length of the single sliding surface in an axial direction is a single sliding length L, whereas in a case where the sliding surface is divided into a plurality of sliding surfaces, a length of one of the sliding surfaces in the axial direction, the one sliding surface having a least length in the axial direction among the plurality of sliding surfaces, is the single sliding length L, and a ratio L/D of the single sliding length L to an external diameter D of the main shaft is less than or equal to 2.0.