9.5 Development of a 5-kWh HTS FESS prototype Ë 355Fig. 9.22:Serious deformation of flywheel rotor at the third calculated eigen-frequency of 433.3 Hz.
the probable vibration. It is better to pass these eigen-frequencies quickly in the actual
operation.
The weight of the flywheel rotor is nearly 433 kg and its axial moment of inertia
is about 22.38 m^2 ⋅kg. The ESC calculated from the moment of inertia at 15,000 rpm is
about 7.66 kWh, which is more than the required 5 kWh. The excess contribution to
ESC comes from the flywheel hub, the PM rotors, and the steel spindle. With a DOD
of 75%, the available ESC of an individual HTS FESS unit is about 5.75 kWh, which is
suited to the practical application. At the first stage, the flywheel rotor will be tested
without the carbon composite. After the preliminary experiments and adjustment of
dynamic balance, the carbon composite will be convolved onto the flywheel hub by
the pre-stressing method. At the first stage, the flywheel rotor has the weight of 340 kg
and axial moment of inertia of 4.1 kg⋅m^2 and an ESC of 1.5 kWh at 15,000 rpm.
9.5.4Motor/generator
The PM synchronous motor can switch between the motor function and generator
function quickly. Thus, it is a suitable choice for the HTS FESS system. Because of
a lack of design and fabrication experience of PM synchronous motor at 400-kW and
15,000-rpm level, a PM synchronous motor with I/O power 100 kW has been designed
and manufactured with outer diameter of 350 mm and height of 370 mm. Because of
the compact configuration and size, the PM synchronous motor can be integrated into
the FESS easily.
The output voltage of this PM synchronous motor is about 600 V DC, which is
lower than the standard voltage of a power supply network for a subway system, 750