STP-2000-2115 Signal Transformer Inc., STP-2000-2115 Datasheet - Page 65

• 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
Temperature Rise
Shielding
www.signaltransformer.com
In power transformers over 25VA, temperature rise becomes a factor. The transformer may be constructed with
materials capable of withstanding higher temperatures and may represent a perfectly valid design yet extra power
dissipation may cause heating of nearby components and will certainly increase the temperature in the transformer’s
vicinity.
The real problem is not the internal temperature of the transformer, so much as the actual increase in watts lost as
heat to its surroundings.
Certain AC power line noise and transients can pass through to the transformer’s secondary because of
inter-winding capacitance. This is a “design specific” problem and is very difficult to analyze.
Whether or not it represents a problem in a particular application can be best determined using empirical methods. If
such feed through is a problem, the most common first step is to select a transformer incorporating an electrostatic
shield between the primary and secondary windings. This effectively reduces the inter-winding capacitance. An
equal and sometimes superior approach is to choose transformers with non-concentric windings. i.e. with primary
and secondary wound side by side rather than one over the other. Both these techniques result in at least an order
of magnitude reduction in capacitive coupling. The “non-concentric” approach however gives superior reductions. It
also results in high insulation resistance, making it simpler to survive higher insulation test voltages. Certain types
of transient feed through cannot be inhibited by transformer design parameters so other approaches such as; line
filters, “MOV’s, or ZNRs (transient surge suppressors) may need to be considered.
% load regulation is defined as: V nl – V fl x 100 %
or the % rise in output voltage
at no load as compared to full load.
Family or Series
14A & 14A-R
IF (International
A41
MPI
HPI
M4L
ST & DST
SPLIT TRAN
PC & DPC
LP (Flathead)
241 & DP241
RECTIFIER
TYPES
Flathead)
Signal Transformer - % Load Regulation
of Standard Transformers
Size or VA Rating
ST, 3, 4, 5, 6 & 7
20, 30 & 56 VA
100 TO 350VA
12, 24 & 48VA
2.5, 5.0, 10VA
200VA-900VA
100VA SIZE 8
2KVA-3.5KVA
24VA & 30VA
SIZES 3, 4, 5
2.4 TO 12VA
SIZES 6 & 7
1 TO 100VA
80 & 130VA
30 & 56VA
500VA OR
2VA-18VA
2.5 & 6VA
3, 6, 10
175VA
OVER
25VA
43VA
ST-2
ALL
V fl
37
Regulation
Approx. %
5% OR
21-27
LESS
4-10
2-4
30
20
20
20
15
10
30
20
20
30
20
20
15
10
10
8
8
8
as a rigorous academic analysis. However, such material is
readily available in the literature (see below). This, we feel,
may help bridge the gap for the working designer.
References
the following are recommended:
10
For more detailed theoretical analysis
1. Reuben Lee, Electronic
2. EE Staff – MIT, Magnetic Circuits &
3. O.H. Schade, Proc. IRE, vol 31,
Toll Free 866-239-5777 • Tel [phone] • Fax [phone]
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©2008 Signal Transformer — Specification subject to change without notice. 07.08
Transformers & Circuits, 1947,
John Wiley & Sons
Transformers, 1943,
John Wiley & Sons
p. 356, 1943
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