According to one embodiment, in a lateral cross section, a rotor core includes a plurality of layers of barrier regions formed to be arranged in a radial direction with intervals in each magnetic pole. Each barrier region includes a flux barrier extending from near a part of an outer circumferential surface through d axis to near another part thereof. At least a flux barrier of a barrier region provided at an outermost circumferential surface side is filled with a nonmagnetic conductive material. A barrier-side edge on a side of the central axis, which defines the flux barrier of the barrier region provided in an outermost circumferential surface side is located within a range of 0.55<2a/R.sup.2 <0.84.

According to one embodiment, in a lateral cross section, a rotor core includes a plurality of layers of barrier regions formed to be arranged in a radial direction with intervals in each magnetic pole. Each barrier region includes a flux barrier extending from near a part of an outer circumferential surface through d axis to near another part thereof. At least a flux barrier of a barrier region provided at an outermost circumferential surface side is filled with a nonmagnetic conductive material. A barrier-side edge on a side of the central axis, which defines the flux barrier of the barrier region provided in an outermost circumferential surface side is located within a range of 0.55<2a/R.sup.2 <0.84.

A rotor for an interior permanent magnet machine (IPM), comprising a rotor core having a plurality of magnetically conductive laminations stacked in a rotor axial direction. The magnetically conductive laminations comprise cut-out portions forming a plurality of flux barriers (FB) radially alternated by flux paths (FP), at least a first part of the flux barriers (FB) housing permanent magnets, at least a second part of the flux barriers (FB) being filled with an electrically conductive and magnetically non-conductive material creating a cage inside the rotor core. The rotor further includes a first and a second short circuit ring positioned at the opposite ends of the rotor core, the first short circuit ring being different from the second short circuit ring.

An end structure for a rotor of an electric machine is attachable to an end of the rotor. The end structure includes a ring arrangement, a rotational axis of which is parallel to that of the stacked rotor, and at least one reinforcing structure at least partly within the ring arrangement. A value of a tensile strength of the at least one reinforcing structure is higher than that of the ring arrangement.

An end structure for a rotor of an electric machine is attachable to an end of the rotor. The end structure includes a ring arrangement, a rotational axis of which is parallel to that of the stacked rotor, and at least one reinforcing structure at least partly within the ring arrangement. A value of a tensile strength of the at least one reinforcing structure is higher than that of the ring arrangement.

A synchronous reluctance type rotary electric machine of an embodiment includes a shaft and a rotor core. The shaft rotates around a rotation axis. The rotor core is fixed to the shaft and includes multi-layered hollow parts having a convex shape toward a radially inward side formed for each pole in cross section. Then, when a center in a circumferential direction of one pole is a pole center, a hollow part closest to the shaft among the plurality of hollow parts is a first hollow part, a hollow part positioned next to the first hollow part is a second hollow part, and a hollow part positioned on a side opposite to the first hollow part with respect to the second hollow part is a third hollow part, a width W1 between the first hollow part and the second hollow part on the pole center and a width W2 between the second hollow part and the third hollow part on the pole center are set to satisfy W1W2.

A synchronous reluctance type rotary electric machine of an embodiment includes a shaft and a rotor core. The shaft rotates around a rotation axis. The rotor core is fixed to the shaft and includes multi-layered hollow parts having a convex shape toward a radially inward side formed for each pole in cross section. Then, when a center in a circumferential direction of one pole is a pole center, a hollow part closest to the shaft among the plurality of hollow parts is a first hollow part, a hollow part positioned next to the first hollow part is a second hollow part, and a hollow part positioned on a side opposite to the first hollow part with respect to the second hollow part is a third hollow part, a width W1 between the first hollow part and the second hollow part on the pole center and a width W2 between the second hollow part and the third hollow part on the pole center are set to satisfy W1W2.

A rotor bar fault in a rotor of an electrical machine having a plurality of rotor bars and an end ring configured to short circuit the rotor bars. The method includes the steps of measuring a first temperature at a first end ring location, and measuring a second temperature at a second end ring location, the second end ring location being different from the first end ring location. As broken rotor bars cause a non-uniform temperature distribution in the end ring, the detection of rotor bar faults can be based on monitored temperatures at different end ring locations.

A rotor bar fault in a rotor of an electrical machine having a plurality of rotor bars and an end ring configured to short circuit the rotor bars. The method includes the steps of measuring a first temperature at a first end ring location, and measuring a second temperature at a second end ring location, the second end ring location being different from the first end ring location. As broken rotor bars cause a non-uniform temperature distribution in the end ring, the detection of rotor bar faults can be based on monitored temperatures at different end ring locations.

An asynchronous starting and synchronous reluctance electric motor rotor, an electric motor and a compressor. The asynchronous starting and synchronous reluctance electric motor rotor includes a rotor core. The rotor core includes: a first magnetic barrier structure, with multiple groups of first magnetic barrier portions arranged at interval along a d-axis of the rotor core; and a second magnetic barrier structure, including two communicating magnetic barrier slots arranged at interval along the d-axis, the two communicating magnetic barrier slots being respectively located on two sides of the first magnetic barrier structure, the communicating magnetic barrier slots being arc-shaped slots extending circumferentially along the rotor core, and slot walls of two ends of the arc-shaped slots being arranged parallel to a q-axis.