參數(shù)資料
型號(hào): DSC-10510-493
英文描述: Converter
中文描述: 轉(zhuǎn)換器
文件頁數(shù): 6/12頁
文件大?。?/td> 110K
代理商: DSC-10510-493
6
Data Device Corporation
www.ddc-web.com
DSC-10510
H-02/02-250
ACTIVE LOAD
Active loads (torque receivers) make it more difficult to calculate
power dissipation.The load is composed of an active part and a
passive part. Figure 5 illustrates the equivalent two wire circuit.
At null, when the torque receiver
s shaft rotates to the angle that
minimizes the current in R2, the power dissipated is at its lowest.
The typical ratio of Zso/Zss = 4.3. For the maximum specified
load of Zss = 2 ohm, the Zso = 2 x 4.3 = 8.6 ohms. Also, the typ-
ical ratio of R2/R1= 2.
In synchro systems with a torque transmitter driving a torque
receiver, the actual line impedances are as shown in Figure 6.
The torque transmitter and torque receiver are electrically identi-
cal, so that the total line impedance is double that of Figure 5.
The torque system is designed to operate this way. The higher
the total line impedances, the lower the current flow at null and
the lower the power dissipation. It is recommended that with
torque loads, discrete resistors be used as shown in Figures 7
and 8.
A torque load is normally at null. Once the torque receiver nulls
at power turn on, the digital commands to the D/S are typically in
smaller angular steps, so the torque system is always at or near
null.Large digital steps, load disturbances, a stuck torque receiv-
er or one synchro line open, however, cause an off null condition.
At null the load current could be zero (See Figure 9 ). If Vac =
Vab, both in magnitude and phase, then, when
a
is connected
to
b,
no current will flow. Pick C1 and C2 to match the phase
lead of R1
Zso. In practice this ideal situation is not realized.
The input to output transformation ratio of torque receivers is
specified at 2% and the turns ratio at 0.4%.The in-phase current
flow due to this nominal output voltage (10.2 V) multiplied by the
% error (2.4/100) divided by total resistance (4 Ohms) = 61mA.
A phase lead mismatch between the torque receiver and the
converter of 1 degree results in a quadrature current of 10.2 V x
sin 1
°
/4 Ohms = 44.5 mA. Total current is the phaser sum 61 +
44.5 = 75.5 mA. Power dissipation is 30 VDC x 75.5 mA rms x
0.9 (avg/rms) = 2.04 Watts. Since this is a light load condition,
even pulsating supplies would be approximating DC supplies.
The
off null
condition power dissipation is quite different. Actual
synchros have no current limiting, so the circuit current is the cur-
rent that the circuit conditions demand.The worst case would be
for a 180 degree error between the two synchros as shown in
Figure 10. For this condition the two equivalent voltage sources
are 10.2 V opposing. The current is (10.2 x 2) / 4 = 5.1 A in
phase.
The power dissipated in the converter is the power supplied by
the ±15 VDC supplies minus the power delivered to the load (30
V x 5.1 A x 0.9) - (10.2 V x 5.1 A) = 87.7 Watts for DC supplies.
This requires a large power supply and high wattage resistors.
The converter output current is typically limited (in the DSC-
10510 case to 0.8 A peak).This limits the power supply to more
reasonable values but introduces another problem
the torque
receiver can hang up in a continuous current limited condition at
a false stable null. The DSC-10510 has special circuits that
sense this continuous current overload condition and sends a
FIGURE 7. D/S EQUIVALENT
REF IN
RH
RL
D/S
2
11/3
2/3
ZSO=8.6
REF
TORQUE LOAD WITH DISCRETE EXTERNAL RESISTOR
1.33
1.33
1.33
S1
S2
S3
RH
RL
S1
S2
S3
D/S
TR
REF IN
REF
FIGURE 8. D/S - ACTUAL HOOK-UP
2
RH
RL
A
D/S
1 1/3
2/3
REF
Zso=8.6
B
C
REF IN
C1
C2
R1
FIGURE 9. IDEAL NULL CONDITION
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