| Capacitors can also be used to operate a
three-phase motor on a single-phase network. These types produces
less torque and requires a high capacitance running capacitor.
Typically 70 F / KW @ 220 VAC. line voltage shown in Fig. 4a.
By moving the capacitor from one network phase to another the rotation
direction can be changed shown in Fig. 4a.
Starting torque is approximately 30% of rated torque. To improve starting
torque a starting capacitor can be applied shown in Fig. 4b.
The
use of three-phase motors on single-phase supply is suitable for driving machines with
no-load initial start and they may only be loaded to about 80% of their rated power.
A typical torque-speed characteristic for a three phase-motor on a
single-phase network is shown in Fig. 4c. |
