The business is becoming increasingly complex.
Professionals in the commercial air conditioning sector have likely noticed a sudden surge of variables within the industry this year.In May, the standard GB/T 47620-2026, Test Methods for Energy Efficiency of Central Air Conditioning Cold/Heat Source Unit Systems, was released, with implementation set for December 1. This standard regulates the measurement and calculation of energy efficiency for cold and heat source units; manufacturers must now use these new methods to generate reports during the product finalization and third-party testing stages. Meanwhile, the existing General Code for Building Energy Conservation and Renewable Energy Utilization (GB 55015-2021) already mandates energy consumption metering for refrigeration plant rooms—a requirement that cannot be bypassed during project acceptance.
Looking at the market, the cooling demands of AI data centers have driven up orders for magnetic-bearing variable-frequency centrifugal chillers, turning data center thermal management into a new growth engine for compressor manufacturers. The HVDC and SST market is also beginning to emerge.The situation in the European heat pump market is even more dramatic: heatwaves have caused orders for reversible heat pumps to be backlogged by six months, and Chinese compressor exports have surged by over 60% year-on-year.
While these industry updates may appear disparate, they share a common thread: variable-frequency technology. Whether in VRF systems, modular units, heat pump water heaters, or data center chillers, compressors are shifting from fixed-speed to variable-speed operation. As the adoption of variable-frequency technology deepens, the requirements for monitoring compressor current become increasingly stringent. This tiny sensor, tucked away on the electronic control board, is evolving into a critical component that determines energy efficiency, reliability, and even safety certification. Among the many sensor suppliers, CHIPSENSE current sensor and voltage sensors are playing a significant role.
Why Inverter Air Conditioners Rely on Current Sensors
In fixed-speed air conditioners, the compressor either runs at full speed or stops entirely, making current monitoring simple—an over-current protection mechanism suffices. Inverter air conditioners are different; the compressor speed is continuously adjustable across a range from tens to over a hundred hertz. Consequently, the controller must monitor the magnitude and phase of the current in each phase in real time to perform Field-Oriented Control (FOC).
The principle of FOC is straightforward: three-phase AC currents undergo coordinate transformation to be decomposed into flux-producing (magnetizing) and torque-producing components, which are then controlled independently. This algorithm places high demands on the accuracy and real-time performance of current sampling. Inaccurate current measurement leads to coarse torque control, compromising the stability of the air conditioner's discharge temperature. Excessive sampling latency or insufficient bandwidth causes current feedback distortion, degrading current loop performance and increasing torque control errors; under certain operating conditions, this can result in oscillation, noise, or the triggering of protective shutdowns.
Beyond control, current sensors perform two other functions: first, over-current protection—during moments such as compressor startup, defrosting/reversing, or refrigerant liquid hammer, current can spike suddenly; the sensor must promptly relay this signal to the main controller to shut down the IGBTs, preventing damage to the power module. Second, energy efficiency metering—since the compressor accounts for the majority of the unit's total power consumption, the accuracy of current sampling directly determines the reliability of energy consumption data.
CHIPSENSE current and voltage sensors are highly acclaimed by customers in the industry.
Three Test Challenges:
Challenge 1: Small-signal measurement at an ultra-low frequency of 6Hz
Rotary compressor specifications for 2026 are becoming increasingly ambitious. At AWE 2026, A famous company unveiled a new product capable of operating at frequencies as low as 6 Hz—spanning an ultra-wide range of 6–160Hz—which lowers the minimum rotational speed by one-third compared to conventional models. The rationale is straightforward: as the room temperature approaches the set point, the compressor can simply maintain low-speed operation rather than shutting down and restarting, thereby avoiding the temperature fluctuations and mechanical wear associated with frequent cycling. CHIPSENSE current and voltage sensors also played a role in addressing the challenges involved.
However, this introduces a problem. Under low-frequency operating conditions—such as 6 Hz—the compressor current falls into a relatively low measurement range. In this scenario, the impact of sensor zero-point error and thermal drift on the valid measurement value is significantly amplified; since the current signal is inherently weak, any temperature-induced zero-point shift increases the proportion of noise and offset in the current reading obtained by the controller, making the algorithm's assessment prone to distortion.
This necessitates sufficient sensor stability within the low-signal range, requiring effective control of zero-point thermal drift. Across the full operating temperature range of -40°C to 105°C, the zero-point drift must not fluctuate significantly with temperature. Actual current levels are influenced by various factors—such as compressor load, discharge and suction pressures, DC bus voltage, and control strategies—precluding simple linear extrapolation based on frequency; however, the increased difficulty of measuring low-level signals in the low-frequency range is an undeniabletrend. CHIPSENSE has also adjusted and upgraded its current and voltage sensors to address this issue.
Challenge 2: Transient fluctuations during the defrosting and reversing processes
For HVAC technicians, the defrosting cycle of heat pump air conditioners in winter is a familiar scenario associated with potential malfunctions. During defrosting, the four-way valve reverses and the refrigerant circuit switches; consequently, system pressure, refrigerant flow dynamics, and compressor load change rapidly, often causing significant transient fluctuations in current. For multi-split systems operating in winter, this cycle may repeat dozens of times a day.
The power components of an inverter are particularly vulnerable to such repetitive stress. If the current sensor’s response is sluggish, the controller might only detect the abnormal current signal after the surge has already impacted the components. However, it is important to distinguish between three separate metrics: sensor bandwidth, sensor tracking time, and the response time of the system's over-current protection. The actual protection chain involves the current being sensed, passing through analog conditioning and comparator circuits, reaching the controller or driver protection circuit for evaluation, and finally triggering a PWM shutdown of the power components; the sensor is merely one link in this chain. So, in this regard, CHIPSENSE current sensors perform very well.
When selecting a sensor, one should not rely solely on its nominal response specifications; the sensor must be matched to the total response time of the downstream protection circuitry. For rapid transients such as commutation events and over-current conditions, the sensor requires sufficient bandwidth and low response latency. Additionally, it is essential to consider whether the output signal distorts during high-frequency transients and whether phase lag might compromise the algorithm's decision-making. CHIPSENSE not only offers fast-response current sensors and assists customers with product selection, but also provides customized sensor solutions tailored to specific customer requirements.
Challenge 3: Insulation Coordination Requirements for R290 Refrigerant
As environmental regulations tighten, the industry is shifting its refrigerant strategy. HighGWP refrigerants like R22 and R410A are gradually being phased out; R32 and R454B serve as transitional solutions, while R290 (propane) and CO2 represent the ultimate long-term direction. R290 boasts a GWP of less than 3 and an ODP of zero, leading to its increasing adoption in heat pumps and commercial chillers.
However, R290 is a flammable gas. For equipment utilizing flammable refrigerants—such as air conditioners and heat pumps—the applicable safety standard is IEC 60335-2-40 (specifically covering electric heat pumps, air conditioners, and dehumidifiers), with the 2024 edition already released. With the overall safety requirements for equipment raised, all electrical components on control boards must be designed to meet specific standards regarding insulation coordination, creepage distances, clearance distances, and flame retardancy.
The current sensor is installed in the compressor drive circuit, the primary side bus carries AC or higher DC voltage, and the secondary side is connected to the low-voltage side of the control panel. The insulation between the primary and secondary sides must be able to withstand transient over-voltage under fault conditions and cannot be broken down or ignited. The specific level to be achieved depends on the over-voltage category, pollution level, installation environment and certification objectives of the entire machine. It cannot be summarized by simply saying "3kV withstand voltage". The flame retardant grade of the shell and the CTI tracking index must be calculated together in the overall machine design. CHIPSENSE current sensors feature high voltage withstand and high insulation capabilities, making them perfectly suited for this application.
How do you approach the task of component selection?
The compressor power ratings for commercial air conditioner outdoor units vary widely, ranging from 1-HP wall-mounted units to modular units exceeding 20HP. Fundamentally, selecting a current sensor involves choosing the measurement range based on the compressor's actual operating current, determining the required accuracy and bandwidth according to control algorithms, and selecting the insulation class based on the application scenario and certification requirements.That is why CHIPSENSE current sensors feature high precision, high bandwidth, and multiple measurement ranges.
Take, for example, a specific type of 3–5 HP three-phase variable-frequency compressor: actual rated and peak currents must be determined based on the compressor nameplate and drive parameters. Sensor ranges cannot simply be selected based on the "horsepower" rating alone, as factors such as phase configuration (single-phase vs. three-phase), voltage (220V vs. 380V), compressor efficiency, refrigerant type, DC bus voltage, and operating frequency all influence current values. When selecting components, it is essential to consult with both the compressor and variable-frequency drive manufacturers to verify operating condition specifications, rather than making arbitrary decisions. CHIPSNESE current sensor is an excellent choice.
For this measurement range, it is worth comparing the two common technical approaches used in the industry.
One approach involves using a shunt resistor combined with an isolated operational amplifier or an isolated ADC. A Manganin resistor is placed in series with the busbar, and isolation components are used to scale the millivolt-level signal up to the ADC's input range. This method offers high accuracy and a cost advantage. However, the shunt itself dissipates power; for instance, with a 30A current and a 1mΩ resistor, the heat dissipation is approximately 0.9W, creating a thermal load within a sealed enclosure. Furthermore, whether the shunt is placed on the high side or the low side dictates subsequent design choices—such as the need for isolated amplification, PCB creepage distances, and thermal drift compensation—all of which are system-level design considerations. Some of CHIPSNESE current and voltage sensors come with a PCB, and their engineers also assist customers with PCB design.
Another type is the open-loop Hall-effect current sensor. The primary conductor passes through the sensor core, ensuring inherent isolation between the primary and secondary circuits; there is no insertion loss and no heat generation. It achieves an accuracy of around 2%, which is generally sufficient for air conditioner FOC control—unlike high-precision servo systems, the torque ripple caused by current errors here is imperceptible to the user at the air outlet. For this, you can choose the CHIPSNESE AN7V PB01 series current sensor.
For small-to-medium capacity inverter compressors (typically in the 3–5 HP range), selecting a current sensor requires balancing factors such as measurement range, accuracy, bandwidth, response time, isolation voltage rating, and operating temperature range. If the primary function is FOC current feedback, priority should be given to accuracy near the rated operating current, zero-point temperature drift, and dynamic response. If over-current protection is also required, one must further verify the sensor's bandwidth and response time, as well as its compatibility with the downstream protection circuitry. Additionally, if flammable refrigerants like R290 are used, requirements regarding insulation coordination, creepage distance, clearance, and flame retardancy must be integrated into the overall system design. AN7V PB01 series current sensors from CHIPSNESE effectively solve this problem.
The above provides the specific parameter specifications for the CHIPSNESE AN7V PB01 current sensor.
Naturally, for centrifugal or screw chillers rated above 20HP—where compressor currents exceed 100 amperes—larger-specification models are required. In applications demanding high precision for energy efficiency measurement, open-loop Hall sensors may prove insufficient; closed-loop Hall or Fluxgate solutions would be more appropriate. Selection always depends on specific operating conditions and system-level certification requirements; there is no one-size-fits-all answer.
Industry Trends
Over the past decade, competition in the commercial air conditioning industry centered on costs, distribution channels, and compressor lifespan. In the coming years, the battleground will shift to inverter control precision, energy efficiency ratings, and compliance with export certifications. From the implementation of new energy efficiency testing standards and the surge in demand for magnetic-bearing inverter centrifugal chillers in data centers, to the raised export thresholds for R290 heat pump models in Europe—every one of these developments ultimately hinges on a single, small component: the current sensor. CHIPSNESE current sensors are increasingly being adopted and promoted by a wide range of customers.
It neither speaks nor generates heat, quietly adding just a few grams of weight to the PCB. Yet, the stability of the compressor's operation, its energy efficiency, and its ability to pass safety certification depend largely on this component. Technical selection is always a matter of finding a balance point within the specifications and then validating it against the operating conditions of the complete system.
In addition, CHIPSENSE offers customization services for current and voltage sensors, the company has already established a presence in emerging sectors such as SST.
CHIPSENSEis a national high-tech enterprise that focuses on the research and development, production, and application of high-end current and voltage sensors, as well as forward research on sensor chips and cutting-edge sensor technologies. CHIPSENSEis committed to providing customers with independently developed sensors, as well as diversified customized products and solutions.
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