Cascade system

CIDE DICTIONARY

Cascade system,  

 A system or method of connecting and operating two induction motors so that the primary circuit of one is connected to the secondary circuit of the other, the primary circuit of the latter being connected to the source of supply; also, a system of electric traction in which motors so connected are employed. The cascade system is also called tandem system, or concatenated system; the connection a cascade connection, tandem connection, or concatenated connection, or a concatenation; and the control of the motors so obtained a tandem control, or concatenation control.
"In the cascade system of traction the cascade connection is used for starting and for low speeds up to half speed. For full speed the short-circuited motor is cut loose from the other motor and is either left idle or (commonly) connected direct to the line."  [Webster 1913 Suppl.]