SECTION
ACME ELECTRIC
•
MILWAUKEE, WI
•
800.334.5214
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acmetransformer.com
52
INDUSTRIAL CONTROL TRANSFORMERS
To make the proper transformer selection,
the load must be completely analyzed...
which involves every electrically energized
component in the control circuit.
All electromagnetic control devices have
two current requirements; the first to
energize the coil; the second to maintain
the contact for a definite period of time.
The initial energizing of the coil, which
takes 5 to 20 milliseconds, requires many
times more current than normal. This is
referred to as
volt-ampere inrush
... which
is immediately followed by the sealed volt-
amperes—the amount of current required
to hold the contact in the circuit.
Easy, five step selection
1.
Determine the voltage and frequency
of supply circuit: Example: 460 Volts,
60 Hz.
2.
Determine the total inrush VA of the
control circuits from the manufacturer’s
data or the contactor data table. Do not
neglect the current requirements of
indicating lights and timing devices
that do not have an inrush VA but are
energized at the same time as the
other components in the circuit. Their
total VA should be added to the total
inrush VA.
3.
Refer to the regulation data chart.
If the supply circuit voltage (Step 1)
is reasonably stable and fluctuates
no more than ± 5%, refer to the
90% Secondary Voltage column. If
it fluctuates as much as ± 10%, refer to
the 95% Secondary Voltage column.
Go down the column you have selected
until you arrive at the inrush VA closest
to, but not less than, the inrush VA of
your control circuit.
4.
Read to the far left side of the chart
and you have selected the continuous
nominal VA rating of the transformer
needed. The secondary voltage that
will be delivered under inrush conditions
will be either 85%, 90%, or 95% of the
rated secondary voltage—depending
on the column selected from the
regulation data chart. The total sealed
VA of the control circuit must not exceed
the nominal VA rating of the transformer
selected from the manufacturer’s data
or the contactor’s data table.
5.
Refer to the specification tables on the following pages to select a transformer
according to the required continuous nominal VA and primary/secondary voltages.
{
Data is most current at time of printing. Contact individual manufacturer for updates.
TABLE 2. Typical Magnetic Motor Starter & Contactor Data
{
60 Hz, 120 Volt, 3-Pole
Selecting Industrial Control Transformers
N.E.M.A. Size
Contactor
00
0
1
2
3
4
5
A
L
500 Series
— 192 192 240
660 1225 2040 1490 VA Inrush
Allen
—
29
29
29
45
69
110
96 VA Sealed
Bradley
53 110 175 240
580 1000
1950
VA Inrush
K Series
15
20
22
31
43
65
98
VA Sealed
Heavy
85
85 100 150
490
900
1200
VA Inrush
ASEA
Duty Series
9
9 11.5
15
35
55
65
VA Sealed
218 218 218 218
310
957
1518
VA Inrush
Furnas
25
25
25
25
26
75
116
VA Sealed
151 151 151 528 1152 1248
2580
VA Inrush
General Electric
24
24
24
60
83
86
191
VA Sealed
210 210 210 210
724
880
1790
VA Inrush
Joslyn Clark
18
18
18
18
30
39
295
VA Sealed
Siemens-Allis
76
76
76 194
365
530
1630
VA Inrush
(formerly ITE Gould)
12
12
12
21
35
40
110
VA Sealed
165 245 245 311
700 1185
2970
VA Inrush
Square D
33
27
27
37
46
85
212
VA Sealed
160 160 160 160
625
625
1700
VA Inrush
Westinghouse
25
25
25
25
50
50
180
VA Sealed
Cutler
A1 Series
87 103 103
—
—
—
1158
VA Inrush
Hammer
15
20
20
—
—
—
100
VA Sealed
(Citation
102 103 103 140
390 1158
1158
VA Inrush
Line)
B1 Series
13
20
20
24
50
100
100
VA Sealed
Inrush VA @ 20% & 40% Power Factor
Nominal
85% Secondary Voltage
90% Secondary Voltage
95% Secondary Voltage
VA Rating
20% P.F.
40% P.F.
20% P.F.
40% P.F.
20% P.F.
40% P.F.
50
362
224
289
179
217
134
75
579
354
462
283
345
211
100
839
522
664
413
489
304
150
1326
842
1003
637
679
431
250
3447
2281
2462
1629
1477
977
300
3894
2618
2812
1890
1731
1163
350
5418
3689
3870
2635
2322
1581
500
6496
4575
4691
3304
2887
2033
750
8377
5811
5913
4102
3449
2393
1000
11329
9005
7789
6191
4248
3377
1500
25519
18803
18013
13273
10508
7742
2000
28178
21600
19372
14850
10566
8100
3000
34797
28391
24562
20041
14328
11690
5000
138500
84542
100000
61058
61550
37574
TABLE 1. Inrush VA
