2 ms·
True, but your electrical output would be variable-frequency AC at the drive terminal. This isn't particularly useful unless you use a back-to-back converter (i
by eigenvector 12y ago
True, but your electrical output would be variable-frequency AC at the drive terminal. This isn't particularly useful unless you use a back-to-back converter (i.e. DC link) to get constant-frequency AC.
- derekp7 12y agoWould it have to be variable? If it goes through a CVT, then you can keep the output whatever speed you want.
- eigenvector 12y agoI'm no mechanical engineer but at first glance the conversion efficiency of using a CVT with a synchronous AC drive (vs. direct coupling the motor rotor and the flywheel rotor and using a variable-frequency induction motor + back-to-back converter) would seem to be lower. Modern VFDs have very high part-load efficiency and we can easily maintain a constant power characteristic through the full speed range by operating in the field weakening mode. One way or another you're losing energy in frequency conversion, it's just a question of whether you do that mechanically (with CVT) or electrically (with back-to-back converters). Also keep in mind that for grid storage devices, we're usually talking about 500+ kW on each flywheel which, at low speed, is A LOT of torque.