Compressor Heating Control Using Multi-Frequency PWM Inverter Drive
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Solution Overview
Problem
Existing heat pump devices and air conditioners face inefficiencies in heating the compressor due to high-frequency single-phase alternating-current power supplies, which lead to reduced heating efficiency and regeneration of high-frequency current without reflux, resulting in attenuated electric current and poor heating performance.
Innovation Solution
A heat pump device configuration that includes a compressor, motor, heat exchangers, an inverter, and an inverter control unit capable of generating PWM signals for efficient high-frequency current feeding, with a heating operation mode that ensures reflux current flow by shifting carrier frequencies and managing switching elements to prevent all-off states, thereby enhancing heating efficiency and reducing electromagnetic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-frequency single-phase alternating-current power supply is used to heat the compressor, then the lubricating action in the compressor is smoothed, but the heating efficiency deteriorates because the current attenuates earlier and does not efficiently flow to the electric motor
Solution Approach 1:
The patent changes the frequency parameter of the alternating current supplied to the compressor motor. By using high-frequency AC voltage (higher than normal operating frequency), the patent achieves both smoothed lubricating action and maintained heating efficiency. The frequency parameter is specifically adjusted to prevent current attenuation while ensuring the current flows efficiently to the electric motor, resolving the contradiction between lubrication quality and heating efficiency.
2Loss of energy
If a high-frequency single-phase alternating-current power supply is used, then an input is reduced and a temperature rise is prevented through a reduction in a current by an amount of the inductance of a winding wire, but rotation of a rotating unit of the compressor is suppressed
Solution Approach 1:
The patent carefully selects the frequency parameter of the high-frequency AC voltage to achieve a balance where the current reduction due to inductance prevents excessive temperature rise, while the frequency remains high enough to suppress rotation of the rotating unit. This parameter optimization ensures that the compressor is heated effectively for lubrication without causing unwanted rotation or excessive temperature increase.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution efficiently feeds high-frequency current to the electric motor, effectively heats the compressor, and reduces electromagnetic noise, improving heating efficiency and energy savings while minimizing environmental impact.
Implementation Method 1
a high-frequency alternating-current voltage is applied to a compressor according to a fall of an outdoor air temperature to heat or warm the compressor
Implementation Method 2
an inverter configured to apply a desired voltage to the motor; and an inverter control unit configured to generate PWM signals for driving the inverter
Data Source
AI summary
A heat pump device that can efficiently feed a high-frequency current to an electric motor and effectively heat a compressor includes a compressor including a compression mechanism configured to compress a refrigerant and a motor configured to drive the compression mechanism, heat exchangers, an inverter configured to apply a voltage to the motor, and an inverter control unit configured to drive the inverter. The inverter control unit includes a stagnation detecting unit configured to determine whether heating of the compressor is necessary and notify the determination result and a high-frequency-alternating-current-voltage generating unit and a PWM-signal generating unit configured to shift to a heating operation mode when the heating is necessary and, in the heating operation mode, generate PWM signals to provide, based on a heating time carrier signal having two or more frequencies, a period in which a reflux current flows.