Iwatsu SY-956, Инструкция по эксплуатации

Страница: 18 / 44

8
Therefore, H
v
is
(4).
Magnetic flux density B
p
inside a single sheet is
(5).
A conventional MC method-based SST is equivalent to measuring the iron loss P per unit volume of a single
sheet from this H
v
and B
p
.
(Whenever “iron loss” is indicated hereafter, it mean iron loss per unit volume.)
Because iron loss P is determined by dividing the area of the B-H curve by the cycle of the excitation signal,
(6),
when formula (2) is substituted into this, it becomes
(7).
The first term of formula (7) is the actual iron loss P
p,
which only includes the magnetic field strength H
p
and the
magnetic flux density B
p
in a single sheet. The second term is related to the iron loss H
ya
in the measuring yoke,
which includes the magnetic field strength in the yoke. A conventional MC method-based SST ignores the
second term of formula (7) by assuming that the magnetic field strength in a measuring yoke H
ya
is small
compared to the magnetic field strength in a single sheet H
p
(H
v
≈ H
p
) in formula (2).
With this instrument, magnetic field strength in the measuring yoke H
ya
, which was unmeasurable with
conventional MC method-based SSTs, can be calculated from this 1st measurement and the 2nd and 3rd,
explained later. Using the value of H
ya
, find the magnetic field strength H
p
of the single sheet and then calculate
the actual iron loss P
p
of the single sheet with only the first term of formula (7).
In the 1st measurement, H
v
and B
p
are calculated by formulas (4) and (5).
The 2nd measurement is explained next.
Reconnect Relay 2 to iii-side. Do not change Relays 1 and 3. From the signal generator, send an excitation sine
wave signal of the same frequency f (cycle T) used in the 1st measurement so that the excitation current i
1a2
,
which flows through the excitation coil on the measuring yoke, is the same as the excitation current i
1a
from the
1st measurement. At this point, an induced voltage V
3a
is generated at both ends of the B coil on the measuring
yoke.
Magnetic flux density B
ya
in the measuring yoke is
(8).
H
v
=
n
1
i
1a
L
p
=
n
1
V
1a
L
p
R
s
B
p
=
1
n
2
A
p
∫ V
2
dt
P =
1
T
∫ H
v
dB
p
dt
dt
T
0
P =
1
T
∫ {H
p
+ (
L
ya
L
p
) H
ya
}
dB
p
dt
dt
T
0
=
1
T
∫ H
p
dB
p
dt
dt
T
0
+
1
T
∫ (
L
ya
L
p
) H
ya
dB
p
dt
dt
T
0
B
ya
=
1
n
3
A
y
∫ V
3a
dt