I. In the 800V high-voltage electric drive era, bearings are becoming a technical bottleneck

The evolution of the electric drive system for new energy vehicles has never been so rapid. From 400V to 800V high-voltage platform, from 16,000 revolutions per minute to 20,000 revolutions per minute or even higher speeds, from traditional round-wire motors to flat-wire oil-cooled motors - each technological iteration is constantly pushing the performance limit of the electric drive system and also posing unprecedented demands on bearings.

 

In the 800V high-voltage electric drive system, the challenges faced by bearings are no longer singular. Axial current electro-corrosion, extremely high rotational speed temperature rise, compact space rigidity - three challenges are simultaneously pressing on this seemingly simple and precise component. Traditional deep groove ball bearings have begun to reach their performance boundaries in the electric drive system, and the industry's pursuit of higher power density and longer range is pushing bearings to the limit.

 

NMT, in response to the special needs of the electric drive system for new energy vehicles, has achieved systematic breakthroughs in three dimensions - materials science, thermal management engineering, and electrical insulation technology - providing a full range of solutions from hybrid ceramic insulation bearings to ultra-high-speed thermal management schemes for the 800V high-voltage electric drive platform.

 

II. Axial Current Electro-corrosion: The Invisible Threat to Bearings in 800V High-Voltage Systems

In the 800V high-voltage electric drive system, the problem of axial current has evolved from a "potential risk" to a "real threat". The application of high-voltage platforms and silicon carbide (SiC) power devices has significantly increased common-mode voltage and axial voltage. When the axial voltage exceeds the breakdown threshold of the bearing oil film, tiny electric sparks penetrate the lubricating film, causing local melting and material transfer on the raceway and rolling elements surfaces, resulting in characteristic "scratched plate-like" wave-shaped damage - this is electro-corrosion.

 

The destructive power of electro-corrosion is gradual but fatal. Initially, the damage is manifested as small molten pits on the raceway surface; as the operating time increases, the molten pits gradually expand into wave-shaped grooves, increasing vibration and noise; ultimately, the bearing fails due to electro-corrosion before reaching its mechanical lifespan.

 

NMT's hybrid ceramic insulation bearing - blocking the conduction path of axial current

 

The fundamental solution to the problem of axial current is to block the conduction path of the current through the bearing. Inserting an "insulation layer" between the rolling elements and the raceway - using non-conductive ceramic materials instead of steel balls.

 

NMT's hybrid ceramic insulation bearing uses silicon carbide (Si₃N₄) ceramic balls instead of traditional steel balls, combined with steel rings, maintaining the mechanical performance of the bearing while increasing its resistance to over 500 MΩ. The non-conductive nature of the ceramic balls completely cuts off the path of axial current through the bearing.

 

In the bench test of the 800V electric drive system, after 3,000 hours of continuous operation, the raceway surface of the NMT hybrid ceramic bearing showed no signs of electro-corrosion, while the traditional steel bearing showed obvious "scratched plate-like" failure after 500 hours.

 

III. Ultra-high Rotational Speed Temperature Rise: Thermal Management Challenges at 20,000 Revolutions per Minute

The rotational speed of the electric drive system is advancing towards 20,000 revolutions per minute or even higher. For bearings, this means a comprehensive change in centrifugal force, frictional heat generation, and lubrication conditions.

 

At ultra-high rotational speeds, the centrifugal force of the steel balls is proportional to the square of the rotational speed. The greater centrifugal force reduces the contact stress on the raceway and accelerates fatigue; higher rotational speeds bring higher frictional heat, and the lubricating grease oxidizes more rapidly at high temperatures, reducing the thickness of the oil film; when the temperature exceeds the allowable limit of the lubricating grease, lubrication failure follows.

 

NMT's three-layer thermal management solution

 

The first layer: Hybrid ceramic bearings reduce heat sources

 

The density of ceramic balls is only 40% of that of steel balls. At the same rotational speed, the centrifugal force of ceramic balls is significantly reduced, resulting in less contact stress and less frictional heat. The measured data show that under the electric drive condition of 20,000 revolutions per minute, the temperature rise of the NMT hybrid ceramic bearing is 15°C to 20°C lower than that of the full steel bearing.

 

Second layer: Low friction cage reduces stirring heat

 

The NMT electric drive bearing uses lightweight engineering plastic cages. During high-speed rotation, the centrifugal load generated is smaller, and the friction between the cage and the rolling elements is lower. The stirring heat is significantly reduced.

 

Third layer: Special high-speed lubricant ensures oil film integrity

 

At ultra-high rotational speeds, the viscosity-temperature characteristics of the lubricant are crucial. The special lubricant for NMT electric drive bearings uses low-viscosity synthetic base oil and a special anti-wear additive system. It maintains stable oil film strength at extremely high shear rates, ensuring that the metal surface is always separated by a complete oil film.

 

Fourth layer: Compact space high rigidity: Bearing large torque in small volume

 

The power density pursuit of the electric drive system leads to the continuous compression of the bearing installation space. Smaller bearings must withstand higher loads and greater torques. Insufficient rigidity of the bearing will directly cause the critical speed of the rotor system to decrease, affecting the high-speed stability and NVH (noise, vibration and harshness) performance of the electric drive system.

 

The NMT electric drive bearing provides maximum radial rigidity and axial positioning accuracy within the limited external dimensions through optimized raceway geometry design and precise preload control, ensuring the stability of the rotor system at high rotational speeds.

 

Fifth layer: Core application map of NMT electric drive bearings

 

New energy vehicle drive motors

 

Front-wheel drive main drive motor, rear-wheel drive auxiliary drive motor, especially high-voltage permanent magnet synchronous motors and asynchronous induction motors. The NMT hybrid ceramic insulating bearing, with its excellent electrical insulation performance and low heat generation characteristics, becomes the preferred solution for the 800V electric drive platform.

 

New energy vehicle generators

 

Power generation motors for range-extended hybrid vehicles, and ISG motors in energy recovery systems. During high-frequency start-stop and continuous high-speed operation, the low friction characteristics and long lifespan of NMT bearings provide reliable rotational support for the hybrid system.

 

Electric drive system reducers

 

High-speed shafts and intermediate shafts of the electric drive reducers. The NMT cylindrical roller bearing provides high radial load-bearing capacity and transmits high torque in a compact space.

 

Sixth layer: Engineering value loop of NMT electric drive bearings

 

The technical system of NMT new energy vehicle electric drive bearings starts with the insulation scheme of hybrid ceramic insulating bearings, through the thermal management scheme of low-friction cages and special high-speed lubricants, and then to the compact space high rigidity design optimized for raceway geometry, forming a systematic solution covering all technical dimensions of electric drive bearings:

 

Electrical corrosion protection layer: The non-conductive nature of silicon nitride ceramic balls raises the bearing resistance to over 500 MΩ, completely blocking the axial current transmission path and eliminating "scratching lines" failure.

 

Thermal management layer: The low density of ceramic balls reduces centrifugal force heating; low-friction cages reduce stirring loss; special high-speed lubricants maintain oil film integrity at extremely high shear rates.

 

Rigidity layer: Optimized raceway geometry design and precise preload control provide maximum rigidity support within the compact external dimensions.

 

In the 800V high-voltage electric drive system, the insulation characteristics of NMT hybrid ceramic bearings ensure that the bearings are not eroded by axial current. At the ultra-high rotational speed of 20,000 revolutions per minute, the low heat generation design of NMT bearings and the special lubricant ensure the integrity of the oil film. In the limited installation space of the electric drive system, the optimized raceway geometry of NMT bearings ensures sufficient rigidity support.

 

Choosing NMT new energy vehicle electric drive bearings is to select a verified precise rotational support solution for the 800V high-voltage electric drive system - making each acceleration smooth and powerful, ensuring that each kilometer of range is not eroded by bearing losses, and keeping the electric drive system efficient and reliable in the entire life cycle of power output.