Table 2 The parameters of the FESS-UPS system.

PMSM

(motor/generator)

Back-EMF coefficient K_e=68.2 V/krpm

Stator inductance of single phase L_q=0.118 × 10⁻³H

Stator resistance R_s=1.55 × 10⁻³Ω

Rated power is 500 kW

Rated current is 460 A

Theoretical efficiency is 91%

Pole pairs p = 4

Current frequency f = 175 Hz

FW rotor

(storage unit of kinetic energy)

Moment of inertia J = 78.34 kgm²

Weight m = 1482 kg

Volume 0.191 m³

Rated speed ω = 10,500 rpm

Active magnetic bearing

(suspension unit)

Displacement stiffness in radial axis − 9300 N/mm

Current stiffness in radial axis 519 N/A

Displacement stiffness in axial axis − 603 N/mm

Current stiffness in axial axis 153 N/A

Passive magnetic bearing

(attractive force)

Attractive force is 16,750 N at 2 mm suspension displacement