We Claim:
1. A heat pump apparatus (100) comprising:
a compressor (1); a condenser (3);
an expansion mechanism (4); and an evaporator (5),
the compressor (1), the condenser (3), the expansion mechanism (4), and the evaporator (5) being configured to perform a refrigeration cycle,
the heat pump apparatus (100) being configured to perform heat transfer in the condenser (3) or the evaporator (5), the compressor (1) including:
a sealed container (10),
a compression mechanism (9) mounted inside the sealed container (10), and
an electric motor (6) configured to rotatively drive the compression mechanism (9),
the compression mechanism (9) being configured to compress a refrigerant, and to be lubricated by a refrigerating machine oil, the electric motor (6) including:
a stator (6s) fixed to the sealed container (10), with a winding wire (7) being wound around the stator (6s) through intermediation of an insulating material (7), and
a rotor (6r) surrounded by the stator (6s), wherein the insulating material (7) comprises:
a wholly aromatic liquid crystal polyester (LCP) synthesized by polycondensation of two or more monomers in total that are p-hydroxybenzoic acid (PHB) as an essential monomer, and at least two additive components selected from five components of 4,4'-biphenol (BP), hydroquinone (HQ), terephthalic acid (TPA), isophthalic acid (IPA), and 6-hydroxy-2-naphthoic acid (BON6) or at least one additive component

selected from three components of hydroquinone (HQ), terephthalic acid (TPA), isophthalic acid (IPA), and
wherein the refrigerating machine oil has a saturated water content of 2% or less at 40 degrees C and a relative humidity of 80%, for 24 Hr.
2. The heat pump apparatus (100) as claimed in claim 1, wherein the refrigerating
machine oil comprises:
a single-component substance or a multi-component substance composed of at least one of an ester-based oil, an ether-based oil, a glycol-based oil, an alkylbenzene-based oil, a poly-α-olefin-based oil, a polyvinyl ether-based oil, a fluorine-based oil, a naphthene-based mineral oil, and a paraffin-based mineral oil.
3. The heat pump apparatus (100) as claimed in claim 1 or 2, wherein the refrigerant
comprises:
any one of a single-component substance composed of difluoromethane (HFC-32), propylene-based fluorohydrocarbon (HFO-1234yf), or ethylene-based fluorohydrocarbon; a multi-component substance composed of two or more of difluoromethane (HFC-32), propylene-based fluorohydrocarbon (HFO-1234yf), and ethylene-based fluorohydrocarbon; and a multi-component substance containing a mixture of difluoromethane (HFC-32) and ethylene-based fluorohydrocarbon, and
a ratio of the ethylene-based fluorohydrocarbon to the difluoromethane (HFC-32) is less than 60 wt%.
4. The heat pump apparatus (100) as claimed in claim 3, wherein the ethylene-based
fluorohydrocarbon comprises:
a single-component substance or a multi-component substance composed of
at least one of trans-1,2-difluoroethylene (R1132(E)), fluoroethylene (R1141), cis-1,2-
difluoroethylene (R1132(Z)), 1,1-difluoroethylene (R1132a), and 1,1,2-
trifluoroethylene (R1123).
5. The heat pump apparatus (100) as claimed in claims 1 to 4, wherein a flame
retardant that inhibits a decomposition reaction of the refrigerant is contained in at

least one of the refrigerating machine oil, a slidable part of the compressor, the insulating material (7), a surface-coating oil of the winding wire, a coating of a lead wire connected to the winding wire, and a cluster connected to the lead wire.
6. The heat pump apparatus (100) as claimed in claim 5, wherein the flame retardant
comprises:
at least one of a halogen-based flame retardant, a phosphorus-based flame retardant, and an antimony compound.
7. The heat pump apparatus (100) as claimed in claims 1 to 6, wherein the refrigerating
machine oil has a saturated water content of 0.2% or less.