VENTILLATING ARRANGEMENT FOR DYNAMO-ELECTRIC MACHINES

A dynamo-electric machine of the natural ventillation type having no forced cooling nor any fan means to increase cooling of the machine utilizes fan-action caused by the rotation of the rotor whereby cooling air sucked into the rotor space provided by a rotor-spider is generally discharged, through radial ducts in the rotor into the machine air gap and finally axially through the machine air gap. Where very high rotational speeds are involved such as in high frequency generators, in order to reduce excessive windage losses caused by all the cooling air discharging axially through the machine air gap, the dynamo-electric machine stator is provided with independent duct systems comprising stator radial ducts in communication with the rotor radial ducts and stator axial ducts in communication with the stator radial ducts so as to substantially divert the cooling air discharge from the machine air gap into and through the stator, thereby reducing windage losses. The stator may be provided with an additional annularly surrounding cooling arrangement.