3.2.3.3 For example, Fig. 3 shows that for BK-200 type, the capacity is 200VA, the input voltage is 380V, and the
output voltage is 36V, 24V. Because the primary side has only one winding, the capacity of this winding is the rated
capacity 200VA; there is a center tap in the secondary winding, so that only when the maximum voltage 36V of the
secondary side is used separately, the 200VA load can be carried. If there is 24V, the 200VA load cannot be carried,
but only 133VA load is carried. Because the total current on the secondary side is I2=
5.55А, the
capacity when the 24V is used separately is 24V = 24V*5.55А = 133VА. when 36V and 34V are both used, the
sum of the currents shall not be greater than 5.55A. In a word, regardless of whether the output voltage is used
separately or two sets are used simultaneously, the sum of the load currents cannot exceed the rated current of the
transformer.
3.2.3.4 For example, Fig. 4 shows that for BK-200 type, the capacity is 200VA, the input voltage is 380V, 220V,
and the output voltage is 110V, 36V, 24V, 6V. Fig. 4 shows that there is a center tap in primary and secondary
windings. The maximum operating current of the primary winding is I1=
0 .526А, so regardless of
whether the 220V or 380V is used, its current cannot exceed 0.526A; even when the 380V is used, the capacity of
this transformer is 200VA; when the 220V is used, the maximum capacity of this transformer is
х 220V =
116VА, so that a 200VA transformer becomes a 116VA transformer; at the same time, the secondary capacity is
reduced to 1l6VA. The maximum working current of he secondary winding depends on the working situations of
the primary winding; if the primary winding is connected to the 380V power supply, at this time the voltage of the
transformer shall be 200VA, so that the current of the secondary winding shall be I2=
1.8А.
When 110V is used separately, the capacity is 110V x 1.8A = 200VA
When 36V is used separately, the capacity is 36V x 1.8A = 65VA
When 24V is used separately, the capacity is 24V x 1.8A = 43VA
When 6V is used separately, the capacity is 6V x 1.8A = 11VA
