24V, 100 rpm Peak Torque, 10⁻⁷ Pa Ultra-High Vacuum: How Wheatstone’s Custom Frameless Vacuum Motors Solve Extreme-Environment Precision Drive Challenges

In semiconductor etchers, space environment simulators, and ultra-high vacuum coating systems, a special class of motor operates under two simultaneous extremes: low voltage (24V) yet delivering high peak torque near zero speed; ultra-high vacuum (10⁻⁷ Pa) where even trace outgassing can ruin the entire vacuum process.

Jiangsu Wheatstone has developed a customisable frameless vacuum motor series that addresses these challenges through direct-embedding frameless design, ultra-high vacuum compatible materials, and lowvoltage, hightorque electromagnetic optimisation.

I. Technical Specification Breakdown: What Do 24V, 100 rpm, and 10⁻⁷ Pa Mean?

1. 24V Low Voltage – Safety and System Constraints

24V is a common lowvoltage level in industrial control and mobile equipment, offering better safety in damp or highcontactrisk environments. However, lower voltage means higher current for the same power, demanding larger conductor crosssections, robust thermal management, and capable drives. To achieve the required torque at 24V, the magnetic circuit must be optimised and the number of pole pairs increased to boost torque density.

1. 100 rpm at Peak Torque – Low-Speed, HighTorque Performance

“Peak torque at 100 rpm” means the motor must deliver maximum torque at very low speed, not during highspeed runs. In vacuum, the absence of air convection makes heat dissipation especially challenging during lowspeed, hightorque operation. This specification tests the motor’s thermal balance and permanent magnet demagnetisation resistance under prolonged stalled or ultralowspeed conditions.

1. 10⁻⁷ Pa Ultra-High Vacuum – Extreme Purity

10⁻⁷ Pa falls into the ultrahigh vacuum range, where gas molecules are extremely scarce. Such environments are found in surface science, particle accelerators, and space simulation. Any trace outgassing from organic materials becomes a serious contaminant. Standard motor components—magnet wire varnish, grease, sealants, plastics—continuously release water vapour and hydrocarbons. Therefore, a 10⁻⁷ Parated motor must be systematically designed for vacuum compatibility from materials to construction.

II. Core Technologies of Wheatstone Frameless Vacuum Motors

1. Frameless Design – Enabling Direct Integration

A frameless motor consists only of rotor and stator components, without a conventional housing, bearings, or shaft. This allows equipment manufacturers to integrate the motor directly into their mechanical structure, eliminating transmission components, increasing stiffness, and—crucially—reducing potential contamination sources inside the vacuum chamber.

1. Low-Voltage, HighTorque Electromagnetic Design

To achieve high torque at 24V and 100 rpm, Wheatstone uses a high number of pole pairs with highgrade NdFeB permanent magnets, increasing torque density through fractionalslot concentrated windings. This results in short end turns, low copper loss, and high slot fill factor within a compact envelope.

1. 10⁻⁷ Pa Ultra-High Vacuum Compatible Material System

Insulation System: Conventional organic magnet wire is replaced with polyimidefilminsulated wire or ceramicinsulated windings. Total Mass Loss (TML) is controlled below 0.1%, and Collected Volatile Condensable Material (CVCM) below 0.01% at 10⁻⁷ Pa. Vacuum Pressure Impregnation (VPI) with solventfree resin fills all voids, eliminating discharge paths and further reducing outgassing.

Bearings and Lubrication: For UHV applications, Wheatstone offers full ceramic bearings (silicon nitride balls) with solid lubricant coatings (MoS₂ or diamondlike carbon), completely eliminating grease volatilisation and enabling longterm maintenancefree operation at 10⁻⁷ Pa.

Hermetic Terminals: Glasssintered feedthroughs fuse metal pins with specialty glass at high temperature, forming an atomiclevel bond with leak rates below 10⁻⁹ Pa·m³/s, capable of withstanding UHV and thermal shock.

Component Pretreatment: Metal parts (stator core, rotor yoke) undergo ultrasonic cleaning and vacuum hightemperature baking before assembly to remove surfaceadsorbed gases.

1. Thermal Management in Vacuum

In UHV, convection cooling is absent; heat is removed only by conduction and radiation. Wheatstone reduces heat generation at the source through optimised electromagnetic design (lower iron and copper losses). A lowthermalresistance path between the stator and the mounting interface, filled with highthermalconductivity potting compound, efficiently conducts heat to the chamber wall or external cooling system.

III. Typical Customisable Parameters (24V / 100 rpm Peak Torque)

All parameters can be tailored to specific applications, from electromagnetic design to mechanical interfaces.

IV. RealWorld Applications

1.Semiconductor PVD Coating System – Wafer Transfer Rotary Stage

In a magnetron sputtering PVD system, the wafer stage must rotate at very low speed under 10⁻⁷ Pa to ensure film thickness uniformity. A Wheatstone custom frameless vacuum motor, with direct drive, achieved speed ripple below 0.1% and repeatability better than ±0.01°, and has operated continuously for over 30,000 hours without failure or contamination.

2.Space Environment Simulation – MultiAxis Sample Manipulator

A space simulation facility required a 10⁻⁵ Pa vacuum with -50℃ to +150℃ thermal cycling. Three degrees of freedom (azimuth, elevation, roll) were driven by Wheatstone frameless vacuum motors. Full ceramic bearings with solid lubrication maintained stable clearance under extreme thermal shock, passing 1,000 temperature cycles.

3.UltraHigh Vacuum Valve Actuator

In a synchrotron beamline, isolation valves must open and close rapidly under 10⁻⁸ Pa. Wheatstone frameless vacuum motors, integrated directly into the valve mechanism, delivered high torque density and fast response, achieving valve actuation times below 0.2 seconds with no particle generation.

V. Conclusion

Three demanding requirements—24V low voltage, 100 rpm peak torque, and 10⁻⁷ Pa ultrahigh vacuum—are met in a single motor through frameless directembedding design, lowoutgassing material systems, Vacuum Pressure Impregnation, and full ceramic bearings with solid lubrication. Wheatstone provides reliable, “invisible” power for extremeenvironment precision motion.

For custom frameless vacuum motor requirements, contact the Wheatstone technical team. From electromagnetic design and material selection to vacuum testing and reliability validation, we offer endtoend customisation.