1.4 KiB
Chapter 11
Withstand current = I_{sc}
Z_{thev} = {V_{nominal} \over I_{sc}}
Dual Voltage Transformers
usually single phase
usually residential
Medium voltage primary
Secondary is (2) 120V secondaries. There’s 3 wires. One thats bare wire (neutral), and 2 wires for power, both at 120V. Just like the transformer that we used in lab.
The transmission lines generally go to multiple households. This makes it easier to balance the load.
Large buildings normally have 208V_{line}, or 120V in a 3-phase, wye power.
Autotransformers
Primary turns N_p
Secondary turns (N_s)
V_s=\frac{N_s}{N_p}\times V_p
Turns ratio a=\frac{N_s}{N_p}
I_pN_p=I_sN_s
I_p and I_s are both down
There’s a problem: Theres no isolation between the primary and the secondary. Its cheaper, but noise problems are still there.
They’re normally labeled, but our professor is an asshole, so we don’t know in lab.
Don’t use a nail as a fuse.
Chapter 12: 3-Phase
It… its just 3 transformers
Delta-Wye configuration
Left is \Delta, right is Y
Name-plate:
480-208 = \Delta-\Delta
$480/277-208/120$=Y-Y
These can be in any combination