2 Phase Induction Motors were once the Industry Standard items - back in the early 1900's.
The 2 Phase Polyphase AC System was used in many areas, and was derived either solely from 2 Phase 4 Wire Distribution, or from 3 Phase 3 Wire Distribution - which was the more common method.
Variations of the 2 Phase Systems + Motors sprouted into some currently used types.
Small Dry-Type Polyphase Transformers are connected as Open Delta "Tee", which was a very common connection technique for 2 Phase 4 Wire Systems derived from 3 Phase 3 Wire Distribution.
These currently used Open Delta Tee Systems range up to 15 KVA, with Voltage Ratings of:
* 480 VAC x 208Y/120V 3 Phase 4 Wire,
* 480 VAC x 240/120V 3 Phase 4 Wire Delta,
* 480 VAC x 240V 3 Phase 3 Wire Delta,
* 600 VAC x 208Y/120V 3 Phase 4 Wire,
* 600 VAC x 240/120V 3 Phase 4 Wire Delta,
* 600 VAC x 240V 3 Phase 3 Wire Delta.
There are also 2 Phase 3 and 4 Wire Servo Motors in use today, for AI (Robotics) and related applications.
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