Alternating current theory and electrical machines
213
described Faraday’s law, which says that when conductor cut a
magnetic field, emf induced that conductor. Collecting the information given the
question into usable form, have:
V
V
N
p
s
p
V
V
230
12
800
.
Try This
Maths
Using the general equation for transformer given above, follow this maths
carefully, step step, the following example.
Example
A 230V 12V emergency lighting transformer constructed with 800 primary turns.21
A simple transformer. symbols:
V
N
V
N
p
p
s
s
Where the primary voltage
Vs the secondary voltage
Np the number primary turns
Ns the number secondary turns
Moving the terms around, have general expression for transformer:
V
V
N
N
p
s
p
s
Vp Vs
Is
Ip
Primary
winding turns
Secondary
winding turns
Steel core
Magnetic circuit through core
FIGURE 10. Therefore, the emf both windings propor-
tional the number turns. Since both windings
are linked the same magnetic flux, the induced emf per turn will the
same for both windings.
Calculate the number secondary turns required
