Vacuum Stepper Motor
Phytron Vacuum Stepper Motors (VSS / VSH) represent the technically mature result of more than 30 years of experience in space technology. Special types of 2 phase hybrid stepper motors are designed for applications in vacuum up to 10-11 mbar. They are optimized for extreme ambient conditions, such as very low and high temperatures or intense radiation.
Challenges in Vacuum:
Particular challenges for vacuum employment of stepper motors are on the one hand material selection and on the other hand the required high temperature durability of the motor. Under vacuum conditions, materials emit particles, especially so at heigher temperatures. These emissions enhance the partial pressures of certain agents and thus limit the achievable pressure, as well as the achievable vacuum class. If the pumping capacity is not sufficient enough, the required vacuum will never be reached when standard motors are used. By mounting specially designed vacuum motors, the outgassing rates of the applied materials are held at such a low level that the required vacuum can be achieved with normal pumping capacities.
A second complex of problems are encountered with the use of standard stepper motors under vacuum conditions: The outgassing materials will not only produce enhanced partial pressures, but the nascent particles can precipitate onto nearby components. When optical devices, ultra pure mirrors or similarly structured elements are placed near the stepper motors they must not generate particulates. The stringent requirements of this industrial sector are fulfilled only by using stainless steel, special insulation materials and processing methods. Among other measures, Phytron relies on assembling in clean rooms.
Thirdly, negligible convection exists in a vacuum. The heat generated is only transported by radiation and thermal conduction. This means special winding insulation materials and these were adapted to handle the high temperatures.