Crankcase heater systems and methods for variable speed compressors
First Claim
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1. A system comprising:
- a compressor including a shell housing a compression mechanism driven by an electric motor in an on state and not driven by the electric motor in an off state;
a variable frequency drive that drives the electric motor in the on state by varying a frequency of a voltage delivered to the electric motor and that supplies electric current to a stator of the electric motor in the off state to heat the compressor;
a control module connected to the variable frequency drive that controls a speed of the electric motor in the on state and that controls the electric current supplied to the stator of the electric motor in the off state;
a compressor temperature sensor that generates a compressor temperature signal corresponding to a compressor temperature;
wherein the stator heats the compressor for a first time period and the control module receives the compressor temperature signal, determines a rate of change of the compressor temperature over a second time period, after the first time period, and calculates an amount of current to supply to the stator based on the rate of change.
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Abstract
A system includes a compressor having a shell housing a compression mechanism driven by an electric motor in an on state and not driven by the electric motor in an off state. The system also includes a variable frequency drive that drives the electric motor in the on state by varying a frequency of a voltage delivered to the electric motor and that supplies electric current to a stator of the electric motor in the off state to heat the compressor.
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Citations
16 Claims
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1. A system comprising:
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a compressor including a shell housing a compression mechanism driven by an electric motor in an on state and not driven by the electric motor in an off state; a variable frequency drive that drives the electric motor in the on state by varying a frequency of a voltage delivered to the electric motor and that supplies electric current to a stator of the electric motor in the off state to heat the compressor; a control module connected to the variable frequency drive that controls a speed of the electric motor in the on state and that controls the electric current supplied to the stator of the electric motor in the off state; a compressor temperature sensor that generates a compressor temperature signal corresponding to a compressor temperature; wherein the stator heats the compressor for a first time period and the control module receives the compressor temperature signal, determines a rate of change of the compressor temperature over a second time period, after the first time period, and calculates an amount of current to supply to the stator based on the rate of change. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method comprising:
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driving a compression mechanism of a compressor with an electric motor by driving the electric motor with a variable frequency drive that varies a frequency of a voltage delivered to the electric motor in an on state, and not driving the compression mechanism with the electric motor in an off state; heating the compressor by supplying electric current to a stator of the electric motor with the variable frequency drive to heat the stator of the electric motor in the off state; controlling a speed of the electric motor in the on state with a control module connected to the variable frequency drive; controlling, with the control module, the electric current supplied to the stator of the electric motor in the off state; generating a compressor temperature signal corresponding to a compressor temperature with a compressor temperature sensor; heating the compressor with the stator for a first time period; receiving the compressor temperature signal with the control module; determining, with the control module, a rate of change of the compressor temperature over a second time period, after the first time period; calculating, with the control module, an amount of current to supply to the stator of the electric motor based on the rate of change. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification