Design and Protection of Constant Torque Application for Atlas Copco Neos Inverter

Atlas Copco Neos frequency converter: a heavy-duty drive solution designed specifically for constant torque air compressor applications

In the field of industrial variable frequency drives, general-purpose variable frequency drives often need to consider multiple load types such as fans, water pumps, compressors, etc., resulting in design compromises and redundancies. However, as a typical constant torque application, air compressors have completely different requirements for frequency converters - long-term high current output, harsh on-site environments, and high reliability requirements. Relying on nearly 20 years of VSD (variable speed drive) air compressor application experience, Atlas Copco launched its independently developed Neos inverter in 2014, which is specially tailored for its GA series oil injected screw compressor, and has now expanded to Z series oil-free air compressor. This article combines official technical materials to deeply analyze Neos' core design philosophy, technical advantages, and applicable scenarios from an engineering perspective.

Why does an air compressor require a "dedicated" frequency converter?

1.1 Constant torque vs. quadratic torque - the essential difference in load nature

The loads of fans and pumps belong to the quadratic torque type, and the power consumption is related to the speed in a cubic relationship. When operating at low frequencies, the current drops sharply, belonging to the "light load" or "standard load" operating conditions. And the air compressor is a constant torque load - regardless of the speed, the required torque is basically constant, the input power is linearly related to the speed, and the average current is significantly higher than the quadratic load. The document clearly states that under a working pressure of 13 bar, the output current of Neos is almost continuously at 80% to 90% of the rated current, which means that the frequency converter must operate in the full load range for a long time.

This operating condition places extremely high demands on IGBT modules, heat dissipation systems, and capacitor lifespan. If the universal frequency converter is not specially designed, it is prone to malfunction in air compressor applications due to overheating, overcurrent, or dust intrusion.

1.2 The cruel test of the on-site environment

The air compressor room commonly faces challenges such as dust, humidity, and high temperature. The IP rating of traditional frequency converters is often insufficient, and the heat dissipation design is difficult to balance protection and cooling. Atlas Copco found from a large number of on-site feedback that the general inverter in compressor applications is prone to failure due to dust accumulation, moisture erosion, instantaneous overcurrent, etc. This is the fundamental driving force behind the birth of Neos - transforming 20 years of on-site experience into targeted hardware design.

Neos' core design philosophy: simplicity rather than simplicity

2.1 "Less is more" - Simplify hardware architecture

Neos only serves Atlas Copco's air compressor, so there are no redundant components. Unlike traditional general-purpose inverters, it is not equipped with unnecessary digital input/output, communication module options, etc., which makes the design extremely compact. The software is also streamlined, with far fewer parameters than traditional systems, making user configuration more intuitive and convenient. All communication is completed through the Elektronikon controller via the CAN bus, without the need for an additional control panel, further reducing fault points.

The direct benefits of this simplification:

Higher reliability: the fewer components, the fewer potential failure points;

Lower lifecycle environmental impact: less electronic waste at disposal;

Simpler maintenance: fewer types of spare parts and lower inventory costs;

Faster configuration: The debugging tool (Neos browser/Speci5) is designed specifically for compressors with very few parameters.

2.2 Optimal balance between protection and heat dissipation - IP5X and 50 ℃ ambient temperature

Neos adopts a compact aluminum shell with a protection level of IP5X (power electronics part), effectively resisting dust and moisture intrusion, suitable for the harshest on-site conditions. The key is that the high protection level does not sacrifice heat dissipation performance - other brands require derating above 40 ℃, while Neos is designed to operate continuously at full load at an ambient temperature of 50 ℃, with a maximum tolerance of 60 ℃ (derating required). This is due to optimized air duct and radiator design, ensuring thermal stability under continuous high current output.

The document emphasizes that Neos has not only passed validation under laboratory conditions, but also undergone durability testing at specially selected harsh sites to ensure reliability under actual operating conditions.

Technical specifications and compliance

3.1 Electrical Parameters

Project specifications

Supply voltage 3-phase 380~460V AC ± 10%

Frequency 50~60Hz ± 5%