DISCUSSION
Exercise:
5. When a 13W system is balanced, the total watts of connected load between the
neutral and one hot wire is equal to the watts of connected load between the
neutral and the other hot wire.
Under these conditions, the currents in the hot
wires are equal and no current flows in the neutral. Hence, you would measure the
current in the neutral wire to determine whether or not the loads were balanced.
(The current should be zero if the system is balanced.)
7. 220 1.73 = 127.1 or 127 volts.
11. Table 1, for a 2,500 man 48' x 110' laundry gives the connected lighting as
8.2 KVA and the connected power load as 27.9 KVA.
This results in a total
connected load of 27.9 + 8.2 or 36.1 KVA. Table 2 gives the demand factor for a
laundry as 1.00. Hence, the demand load is 36.1 x 1.00 or 36.1 KVA.
13.
Table 1D.
Solution to exercise 13.
1
Table 1, attached memorandum.
2
Table 2, attached memorandum.
Referring to Table 1D, this system is predominantly motors (107.8 KVA) with some
lighting (21.99 KVA). From Table 3, attached memorandum, generator factor for this
type of load is 0.85.
Generator capacity (KW) =generator factor X sum of
individual demands (KVA), giving 0.85 x 122.59 = 104.2 KVA.
14. Enough
excess
generator
capacity
should
be
provided
to
supply
maximum demand when the largest generator is out of service. Two 60 KW and one 30
KW
will
provide
150
KW,
which
is
enough
to
supply
the
required
capacity,
but
provides
no
excess
generating
capacity.
Two
100
KW
generators
will
supply
the
required
capacity,
but
only
when
1-2
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