Special‐impedance transformer
means any transformer built to operate at an impedance outside of the normal impedance range for that transformerʹs kVA rating. The normal impedance range for each kVA rating for liquid‐immersed and dry‐type transformers is shown in Tables 1 and 2, respectively.
Table T-1
Normal Impedance Ranges
for Liquid-Immersed Transformers
|
Single‐phase |
Three‐phase | ||
|
kVA |
Impedance (%) |
kVA |
Impedance (%) |
|
10 |
1.0–4.5 |
15 |
1.0–4.5 |
|
15 |
1.0–4.5 |
30 |
1.0–4.5 |
|
25 |
1.0–4.5 |
45 |
1.0–4.5 |
|
37.5 |
1.0–4.5 |
75 |
1.0–5.0 |
|
50 |
1.5–4.5 |
112.5 |
1.2–6.0 |
|
75 |
1.5–4.5 |
150 |
1.2–6.0 |
|
100 |
1.5–4.5 |
225 |
1.2–6.0 |
|
167 |
1.5–4.5 |
300 |
1.2–6.0 |
|
250 |
1.5–6.0 |
500 |
1.5–7.0 |
|
333 |
1.5–6.0 |
750 |
5.0–7.5 |
|
500 |
1.5–7.0 |
1000 |
5.0–7.5 |
|
667 |
5.0–7.5 |
1500 |
5.0–7.5 |
|
833 |
5.0–7.5 |
2000 |
5.0–7.5 |
|
|
|
2500 |
5.0–7.5 |
Table T-2
Normal Impedance Ranges
for Dry-Type Transformers
|
Single‐phase |
Three‐phase | ||
|
kVA |
Impedance (%) |
kVA |
Impedance (%) |
|
15 |
1.5–6.0 |
15 |
1.5–6.0 |
|
25 |
1.5–6.0 |
30 |
1.5–6.0 |
|
37.5 |
1.5–6.0 |
45 |
1.5–6.0 |
|
50 |
1.5–6.0 |
75 |
1.5–6.0 |
|
75 |
2.0–7.0 |
112.5 |
1.5–6.0 |
|
100 |
2.0–7.0 |
150 |
1.5–6.0 |
|
167 |
2.5–8.0 |
225 |
3.0–7.0 |
|
250 |
3.5–8.0 |
300 |
3.0–7.0 |
|
333 |
3.5–8.0 |
500 |
4.5–8.0 |
|
500 |
3.5–8.0 |
750 |
5.0–8.0 |
|
667 |
5.0–8.0 |
1000 |
5.0–8.0 |
|
833 |
5.0–8.0 |
1500 |
5.0–8.0 |
|
|
|
2000 |
5.0–8.0 |
|
|
|
2500 |
5.0–8.0 |