CONCATENATION

51

as the first motor carries the exciting current of the second
motor.

• The total self-inductive impedance of the couple is that of
both motors in series:

thus the characteristic constant of the concatenated couple is:

*' = y'z'

= 4yz

that is, four times as high as in a single motor; in other words,
the performance characteristics, as power-factor, etc., are very
much inferior to those of a single motor.

With three motors in concatenation, the constants of the
system of three motors are:

7" = 37,
Z" = 3 Z,

thus the characteristic constant:

$" = y"z"

or nine times higher than in a single motor. In other words,
the characteristic constant increases with the square of the
number of motors in concatenation, and thus concatenation
of more than two motors would be permissible only with motors
of very good constants.
The calculation of a concatenated system of three or more
motors is carried out in the same manner as that of two motors,
by starting with the secondary circuit of the last motor, and
building up toward the primary circuit of the first motor.