DOCUMENT 1218
REV. B
Instruction Manual
AGS-LED
312 LED Series
300mm and 400mm
22
10.5.5
Isolation Transformer Information
Isolation transformers are specified and designed for incandescent lamps operating at 6.6A.
Isolation transformers can only provide the power they are design to. The available power will
decrease as the current is lowered due to constrained voltage inherent in the design.
For example: a 100W transformer has a rated voltage of 100W/6.6A=15V. The transformer is
rated for 15V. This means at 2.8A the transformer can only provide 2.8A*15V=42W. Also
transformers should only be used up to 80% of their specified value, so 42W would be 34W.
This is fine when operating incandescent lamps, the required power drops with the CCR current.
Signs are constant power, they do not dim. They require the same power at each CCR step, so
they need more voltage at lower steps than the transformer is designed to supply at 6.6A.
For example: a 100W sign requires a maximum voltage of 100W/2.8A=36V. The isolation
transformer would need to be 36V*6.6A/0.8=298W.
The following table lists the standard transformers with de-rated power capability at each CCR
step current.
Table 5. Isolation Transformer Size Explanation
10.5.6
Isolation Transformer Improperly Sized
a.
Verify the isolation transformer is sized properly. See
Tables 10 - 16, pgs. 80, 81, 82, 84, 86,
88, and 89
for prescribed transformer sizes. Note: an isolation transformer that is too small
cannot provide the necessary voltage at lower current steps to run the sign. See
Section
10.5.5, pg. 22,
and
Table 5, pg. 22,
for transformer sizing explanation.
b.
Note, some regulator technologies require rated load be applied for clean operation. A lightly
loaded regulator paired with an undersized isolation transformer cannot provide the required
voltage to run the sign at lower CCR steps.
c.
If the isolation transformer is too small, remove the transformer and replace with one of
appropriate size.
d.
Return power to the sign. Verify that the sign illuminates.
e.
If problem still persists see
Section 10.5.3, pg. 19,
for other possible action steps.
One Step
Max
Voltage
6.6
5.2
4.1
3.4
2.8
6.6
5.5
4.8
5.5
10/15W
2.27
12
9
7
6
5
12
10
9
10
25W
3.79
20
16
12
10
8
20
17
15
17
45W
6.82
36
28
22
19
15
36
30
26
30
65W
9.85
52
41
32
27
22
52
43
38
43
100W
15.15
80
63
50
41
34
80
67
58
67
200W
30.3
160
126
99
82
68
160
133
116
133
Five Step
Three Step
Available Power