6a,b
Assume the four notches is roughly the same
600𝑋10−6
𝑋360° = 10.8°
0.02
Figure 1:Measure and
Figure 2:Three-Phase Diode Rectifiers-Resistive load
Inferred the source inductance causes cause of
10.8
𝛿𝑉 ↓= 1.35𝑋100𝑙−𝑙 𝑋𝑐𝑜𝑠0°𝑋(
) = 4.05𝑉
360
calculate the width of
the notch
the four concave points; when power is
𝐿𝑠 =
𝛿𝑉𝜋
= 15.57𝑚𝐻
2𝜋50 ∗ 2.6
When V_RN and V_BN are protruding, the DC wave is at decrease; on the
transferred to the Rectifier from the transformer,
the cable will generate source inductance. The
contrary, When V_RN and V_BN are sunken, the DC wave is at increase. That in
line with speculation. When short circuit the current will increase, the voltage
source inductance cause the current
drop to zero rely on other phase maintain output.
commutation cannot complete immediately; it
will have a short-moment short circuit.
Figure 4:Three-Phase SCR Rectifiers-Resistive load
Figure 5:Average Rectifier Load Current and DC Output Voltage vs. SCR Firing Angle
It can be seen from the correct figure a linear relationship in rough. The DC current
curve (blue) is multiplied 10 times for observation.
<—— The firing angle is bigger than 90°;
Figure 3:Idc When 𝜶 = 𝟔𝟓°
conduction ceases entirely because There
I_d=Idc,I_dc(av)=1.13A close to the data set, and
is not enough time for all three phases to
start to discontinuous, therefore, the α≥60, DCM
proceed simultaneously.
The firing angle determines the delay between
three-phase,in pure resistive load, the phase
shift should be zero. The firing angle determines
Figure 6:Figure 3:Idc When α=90°
In ideal state, the diode should not have
any voltage drop, in reality there will be a
voltage drop of about 0.7V , also the
current commutation will not zero delay is
the real situation. Source inductance
caused by power long distance/middle
distance transmission .There will be
the delay between three-phase; in pure resistive
load, the phase shift should be zero, each phase
120°(Positive 60°, Negative 60°); therefore, if the
α≥60, The next phase cannot conduct a smooth
commutation, into discontinued mode.
7a
The inductor stores and releases energy during the threephase transitions, changing the DC output current more
smoothly.
Figure 8:7a1.Three-phase diode rectifier Resistive Inductive Load
The DC current is 2.5125A,2.608A
The AC current is 2.1161A,2.155A
7a2:Compared with pure resistance loading, the RL load's dc current
The AC voltage is 100.49V,99.5V
curve is smoother. The inductance has the function of compensating
The DC voltage is 125.77V,124.86V
the current.
red word is the 6a pure R load
7a3: Because of scaling limitations, the observed data set is not
7a4: From the data set, the load inductance has a
significantly different. However, the inductor in the RL load will
compensatory effect on AC and DC indirectly. The
release the stored energy, thus increasing the output voltage in the
inductance causes a phase shift between the input
discharge phase; the average DC voltage will differ slightly.
voltage and current for the AC. The current lagged
behind voltage when the present handover was
another phase; the current local minimum shifting
three-phase overlapping case smoother of the AC
current. For dc current, store energy when Idc max,
release energy when Idc min.
7b2: Compare this with 6b, when the α
Figure 7:7b1-Three-phase SCR rectifier-RL-load
is 75, the RL-load of SRC still is CCM,
the R load SCR into DCM (α > 60)
7b3:90°, current has entered negative.
7b4: The voltage and current go
negative faster, distorted Waveforms in
the firing angle bigger that 90°.
7b5: Similar in this stage of CCM, the
waveform is smoother, α> 90° the wave
starts to be distorted.
7b6: R-load
60 <α ->DCM ,RL load 60
<α <90 still CCM.
Figure 9:Q7b2&b5—Average Rectifier Load Current and DC Output Voltage vs. SCR Firing Angle
8
8a2:
The DC current is 0.9245mA
The DC voltage is 128.9V
The AC current is 1.0563A
The AC voltage is 57.91V
Figure 10:8a1_Three-phase Diode Rectifier RC-load
8a2: Observe from data set, you can
see that dc current and voltage are
very flat, almost straight. The shunt
capacitor filter reduces ripple voltage
It is corresponding with RC circuit
characteristics.
8a3: The Y-axis range is 0.93 to 0.95 , the minimum value is about
0.93 it was not drop to zero, it is continuous.
Figure 11:8a3—dc current Ir