Acme Electric INDUSTRIAL CONTROL TRANSFORMERS Selection Table
SECTION
5
SECTION
INDUSTRIAL CONTROL TRANSFORMERS
Selecting 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 voltamperes—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.
TABLE 1. Inrush VA
Inrush VA @ 20% & 40% Power Factor
Nominal
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
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.
TABLE 2. Typical Magnetic Motor Starter & Contactor Data ①
60 Hz, 120 Volt, 3-Pole
N.E.M.A. Size
Contactor 00 0 1 2 3 4 5
A L
Allen — 29 29 29 45 69 110 96 VA Sealed
Bradley
53 110 175 240 580 1000 1950 VA Inrush
ASEA
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
210 210 210 210 724 880 1790 VA Inrush
Joslyn Clark
Siemens-Allis
(formerly ITE Gould)
165 245 245 311 700 1185 2970 VA Inrush
Square D
160 160 160 160 625 625 1700 VA Inrush
Westinghouse
Cutler
Hammer
(Citation
Line)
500 Series
K Series
Heavy
Duty Series
24 24 24 60 83 86 191 VA Sealed
18 18 18 18 30 39 295 VA Sealed
76 76 76 194 365 530 1630 VA Inrush
33 27 27 37 46 85 212 VA Sealed
25 25 25 25 50 50 180 VA Sealed
A1 Series
15 20 20 — — — 100 VA Sealed
102 103 103 140 390 1158 1158 VA Inrush
B1 Series
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.
① Data is most current at time of printing. Contact individual manufacturer for updates.
— 192 192 240 660 1225 2040 1490 VA Inrush
15 20 22 31 43 65 98 VA Sealed
85 85 100 150 490 900 1200 VA Inrush
9 9 11.5 15 35 55 65 VA Sealed
12 12 12 21 35 40 110 VA Sealed
87 103 103 — — — 1158 VA Inrush
13 20 20 24 50 100 100 VA Sealed
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ACME ELECTRIC • MILWAUKEE, WI • 800.334.5214 • acmepowerdist.com
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