STP-2000-2115 Signal Transformer Inc., STP-2000-2115 Datasheet - Page 63

• Manufacturer Part Number: STP-2000-2115
• Description: Power Transformers & High Frequency Magnetics Your One Source For All Your Magnetics Needs!
• Manufacturer: Signal Transformer Inc.

How to Specify Power Transformer & Filter Parameters
Transformer Secondary Current
Dual Complementary Supply
www.signaltransformer.com
VNOM divided by VLOWLINE is the ratio of nominal AC line voltage to the specified low line conditions.
A sample calculation appears below for a supply requiring an output of 5V DC at 2A with a minimum input voltage
specification of 95V RMS.
V
V
V
V
V
As a result VAC would be reformulated as:
so that the transformer’s secondary voltage now computes to approximately 10.5V.
It remains to determine the transformer’s required RMS secondary current. This can only be precisely determined by
complex analysis. However, for practical engineering purposes the following chart may be used:
*Even though choke input filters were excluded from this discussion, they are included for reference.
For instance, in the example above (5 V, 2A DC supply) the transformer RMS current would be:
1.2 x 2 = 2.4 A for a FWCT configuration or…
1.8 x 2 = 3.6 A for a Bridge configuration
The total transformer specification would then be:
One more common example is as follows; a dual complementary supply for +/- 15 V @ 100 mA DC.
V
Full-Wave
Center-Tap
Full-Wave
Center-Tap
Full-Wave
Bridge
Full-Wave
Bridge
Full-Wave
Center-Tap
Full-Wave
Center-Tap
Full-Wave
Bridge
Full-Wave
Bridge
V
OUT
REG
RECT
RIPPLE
AC
0.9
0.9
AC =
Rectifier
Rectifier
AC =
Circuit
Circuit
bridge
FWCT
bridge
FWCT
Type
Type
=
= 5V
= 3V
= 1.25V
9.75
= 0.5 (1V
0.9
(15 + 3 + 1.25 + 0.75)
0.9
11
VRECT = 1.25
VRECT = 1.25
Choke Input
Capacitor
Input
Choke Input
Capacitor
Input
Choke Input
Filter Type*
Capacitor
Input
Choke Input
Capacitor
Input
Filter Type*
18.5 CT @ 2.4A
X
18.5 CT @ 2.4A
RMS = 43.2 VA
RMS = 43.2 VA
RMS = 36 VA
RMS = 36 VA
X
10.5 @ 3.6A
10.5 @ 3.6A
Secondary
1.2 x 2 = 2.4 A
1.8 x 2 = 3.6 A
Secondary
1.2 x 2 = 2.4 A
1.8 x 2 = 3.6 A
PP
Rating
0.9
Rating
115
95
115
)
95
95 M2
95 M2
X
X
0.7 x DC Current
0.7 x DC Current
1.2 x DC Current
1.2 x DC Current
DC Current
DC Current
1.8 x DC Current
1.8 x DC Current

Secondary Current
Secondary Current
1

1
Required RMS
Required RMS
Possible “Signal”
Possible “Signal”
ST-7-10, 241-6 or
ST-7-10, 241-6 or
X
Rating
241-7-20, 36-1
Rating
241-7-20, 36-1
= 9.27 V
= 10.46 V
7-10, 10-4
7-10, 10-4
115
95
Parts
Parts
AC
X
AC

1
= 19V
8
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