Heat pump apparatus with compressor heating control
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Solution Overview
Problem
Conventional heat pump apparatuses face challenges in efficiently heating compressors while preventing an increase in circuit size, particularly due to the need to detect and adjust for the rotor stop position to maximize heat output, which often requires complex and bulky motor voltage detection circuits.
Innovation Solution
A heat pump apparatus that includes a compressor, a heat exchanger, an inverter, a current detection unit, a drive-signal generation unit, a magnetic-pole position estimation unit, a steady heating control unit, and a control switching determination unit, which estimates the rotor's stop position using current values and applies high-frequency voltage to achieve efficient heating without rotating the motor, thereby preventing circuit size increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a motor voltage detection circuit is used to estimate the rotor stop position, then the precision of rotor position estimation is improved, but the device complexity and circuit size increase
Solution Approach 1:
The patent extracts only the necessary information (current values) from the motor system to estimate rotor position, eliminating the need for separate voltage detection circuits. The current detection unit already present in the system is utilized to derive position information through calculation, rather than adding dedicated voltage sensing hardware.
Solution Approach 2:
The current detection unit serves multiple functions: it detects motor current for normal operation control and simultaneously provides data for rotor position estimation during heating mode. This multi-functional use of existing components avoids adding dedicated position sensing circuitry.
2Productivity
If the rotor stop position is not accurately estimated, then the device complexity is reduced, but the heating efficiency of the compressor decreases
Solution Approach 1:
The system uses feedback from current detection to continuously estimate rotor position and adjust the high-frequency voltage application accordingly. The control unit monitors current values and uses this feedback to determine the optimal magnetic pole position for maximum heating efficiency.
Solution Approach 2:
The patent replaces complex mechanical or electrical position sensing mechanisms with a computational approach. By using mathematical calculations on current values, the system estimates rotor position without physical sensors or complex detection circuits, achieving high heating efficiency through software-based control.
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 enables efficient heating of the compressor while maintaining a compact circuit size, allowing for stable and efficient heat output regardless of the rotor's stop position, thus avoiding refrigerant stagnation and reducing costs associated with larger circuitry.
Implementation Method 1
a magnetic-pole position estimation unit that changes a voltage phase of a voltage command value for a high-frequency voltage, and estimates a magnetic-pole position indicating a stop position of the rotor from a current value
Implementation Method 2
uses, as a main heat source, iron loss of the motor caused by application of the high-frequency voltage
Implementation Method 3
the drive-signal generation unit applies the high-frequency voltage to the motor to heat the compressor
Data Source
AI summary
A heat pump apparatus includes: a compressor including a motor; an inverter that applies a desired voltage to the motor; a current detector that detects current flowing to the motor; a drive-signal generation unit that generates a drive signal for the inverter; a magnetic-pole position estimation unit that changes a voltage phase of a voltage command value for a high-frequency voltage, and estimates a maximum-heat-amount acquisition magnetic-pole position when the generation unit applies the high-frequency voltage to the motor to heat the compressor; a steady heating control unit that determines an amplitude and voltage phase of the voltage command value from the maximum-heat-amount acquisition magnetic-pole position and a defined necessary amount of heat when the generation unit applies the high-frequency voltage to the motor to heat the compressor; and a control switching determination unit that causes one of the estimation unit and the heating control unit to operate.