Low frequency self-exciting commutator generator

SELF-EXCITING a-c commutator generators have for some time been considered as sources of electrical power. However, what is probably the first commercial use of this type of generator as the prime source of energy for a power machine has recently been made. It is a 6-pole 1,200-rpm 3-phase machine rated 40 kva, 235 volts, 2.5 cycles, and is driven by a squirrel cage induction motor. The set supplies power to one or more 200 hp super-calender induction motors in order to secure threading operation at very low stable speeds. The generator is compounded for approximately flat voltage and frequency. Commutation has been found to be excellent and the voltage wave form is satisfactory.