''

400 ELECTRICAL APPARATUS

Hence, (80) substituted in (79) gives:

0 = h (Z + Z,) - c,Zh + jSet,

,
-h

JSet

— ff •

//

Hence:

and actual value of short-circuit current:

where:

b = °, a fairly large quantity, and

c4 = reduction factor of brush short-circuit
to armature circuit.

The commutation current then is:

/,=/!- /'4

- *1^ "^ f coZ
Substituting (81) (iud (80) into (77), gives:
1 — jSt\± (to — jS) — t]

r __ v.....

Z AZ — jSco — XiCo (CD ~~ j/S)

or, denoting:
it is:

It is, approximately:

(Co ~ J5) -

ZK

hence:

A — 3 —
A3 - •£• - Co'

X2 = 0,

JiC = Co (1 — c0X4) (c0 - jS),
r — e 51.' — jSt\t (CQ — jiS) }

- CoX4)(c0 -jS)

- c0X4) IcT17^ "" ;"

(81)

(82)

(83)

(84)

(85)
(86)
(87)
(88)