Saturday, February 24, 2024

Refrigerator Compressor Reference Design With BLDC Sensorless Control 

By Nidhi Agarwal

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The refrigerator compressor design includes a brushless DC motor with sensorless control, improving efficiency and offering effective temperature control and food preservation.

BLDC

Refrigerator compressors are essential components in modern refrigeration systems, playing a pivotal role in preserving food and maintaining optimal temperature control. As the heart of the refrigeration cycle, they compress and circulate refrigerant, effectively removing heat from the interior to keep food fresh and safe. The efficiency and reliability of refrigerator compressors directly impact energy consumption, operational costs, and the appliance’s longevity. Their importance cannot be overstated, as they ensure the practical functionality of refrigerators in homes and businesses and contribute significantly to reducing food waste and maintaining health standards. This makes advancements and improvements in compressor technology, like integrating Brushless DC motors (BLDC), crucial for enhancing overall refrigeration efficiency and sustainability.

The NXP semiconductors’ refrigerator compressor reference design with a brushless DC motor (BLDC) sensorless control offers greater efficiency using a field-oriented control (FOC) based on the MC56F82xxx controller. The growing use of BLDC motors in reciprocating refrigerator compressors is driven by their ability to improve efficiency. The design constraints of compressors, which lack the space for installing sensors, necessitate using a sensorless controller for these motors.

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The motor drive board of this system is designed with features focusing on efficiency and performance. It boasts a low power consumption, requiring less than 0.6 W during standby mode. In terms of input, the board can handle an input voltage range from 80% to 110% of the rated mains voltage. The control aspect of the system is managed by a high-performance VF refrigerator compressor control solution, which aligns with Class 1 energy efficiency standards. This includes a sensorless field-oriented control (FOC) with both speed and current in closed-loop control. Additionally, the controller used in this system is IEC60730 certified, ensuring compliance with international safety standards.

A typical refrigerator has two main control segments: the compressor control and the system control. The system control primarily monitors the temperatures of various compartments and the surrounding environment. Based on these readings and a predefined control strategy, it regulates the compressor speed, fan states, and the operation of the defrost heater in the fridge. This segment also manages a control panel with a display and key inputs. It sends out a PWM (Pulse Width Modulation) signal, where the signal’s frequency determines the compressor’s operational speed, typically translating a range of 40 Hz to 150 Hz into 1200 RPM to 4500 RPM for the motor.

In the current market, these system and compressor controls are often executed on separate Microcontroller Units (MCUs). A standard refrigerator might contain a system control board, a compressor control board, and a Human-Machine Interface (HMI) module. However, integrating both parts on a single board is feasible, which can eliminate the need for a separate set of AC-DC power circuits.

NXP has tested this reference design. It comes with a Bill of Material (BOM), schematics, etc. You can find additional data about the reference design on the company’s website. To read more about this reference design, click here.

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