Lecture 9 synchros - transmitters, differentials, governing equations

Synchros - transmitters, differentials, governing equations

1. ICE 3015: CONTROL SYSTEM
COMPONENTS Class 9: Synchros–Transmitters,
Differentials, Governing Equations
Dr. S. Meenatchisundaram
Email: [email protected]
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

2. Recall:
• Synchros areelectromechanical deviceswhich produce an
output voltagedepending onangular positionof the rotor and
not on rotor speed and it isdifferent from a DC generator.
• The trade name for Synchros areSelsyn, AntosynandTelesyn.
• Functionally, they resembletransformerswhose primary to
secondary magnetic couplings may be varied by physically
changing the relative orientationof the two windings.
• The four basic types of Synchros
—transmitter
—receiver
—Transformers and
—Differentials
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

3. Transmitter:
• This is a mechanical to electrical transducer which consis ts of a
transformer coreiron asstatorshown in figure.
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

4. Transmitter:
• The basic principle of the synchro is that the voltage induc ed in
the secondary depends on theangleat which the magnetic lines
of the flux cut the turns.
• This induced voltage will vary from a maximum of 1 when the two
windings are in line are parallel to 0 when they are perpendic ular.
• Three poles, equally spaced at 120°are attached to the stat or with
windings S
1
, S
2
, and S
3
.
• One end of each of three winding is connected internally to e ach
other to form a Y.
• The other ends are for external connection.
• Inside the core of the stator the rotor rotates with a single winding
brought out and connected through slip rings for unlimited r otation.
• The rotor is a primary winding and the stator is secondary wi nding.
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

5. Transmitter:
• In the above figure, S
2
and rotor are inline and maximum voltage
is induced in S
2
.
• The voltage induced in S
1
and S
3
are less.
• As the rotor rotates, the induced voltage will be
E
s2
= K E
R
cos ɵ
Where,
E
s2
– rms voltage in stator coil 2
E
R
– rms voltage in rotor
K – proportionality constant (depends on mag coupling & no. o f turns)
ɵ- rotor angle in anti clockwise direction
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

6. Transmitter:
• The voltage induced in S
1
and S
3
can be given as
E
s1
= K E
R
cos (ɵ+120°)
E
s3
= K E
R
cos (ɵ-120°)
• The voltage between respective terminals can be given as,
E
s31
=
3
C
K E
R
sin ɵ
E
s12
=
3
C
K E
R
sin (ɵ - 120°)
E
s23
=
3
C
K E
R
sin (ɵ + 120°)
• The waveform representation is shown in figure below
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

7. Transmitter:
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

8. Example:
• The voltage applied to the rotor of a synchro transmitter is 28V rms. The
rotor shaft is moved 60°from the zero position towards clockwise d irection.
Determine the stator voltages w.r.t the common stator connection f or k=1.
Also determine the voltages between terminals S
1and S
2, S
2and S
3and
S
3and S
1. Take S
2as the reference winding.
Solution:
• Es
2= K E
Rcosɵ= 1 x 28 x cos 60°= 14V
• Es
3= K E
Rcos (ɵ+ 120°) = 1 x 28 x cos (60°+ 120°)= - 28V
• Es
1= K E
Rcos (ɵ- 120°) = 1 x 28 x cos (60°- 120°)= 14V
• Es
31=
3
C
K E
Rsinɵ= 42V
• Es
12=
3
C
K E
Rsin (ɵ- 120°) = - 42V
• Es
23=
3
C
K E
Rsin (ɵ- 120°) = 0V
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram, MIT, Manipal, Aug
–
Nov 2018

9. Receiver:
• In synchro transmitter, the terminal voltage is governed b y angular
position of the rotor.
• In synchro receiver it is the reverse, that is, it will act as a voltage to
position transducer.
•A single phase voltage is applied to each of the three stator
winding and ac excitation to the rotor winding and mutual
repulsion gives the angle of the rotor shaft.
• Initially the magnetic field set by the stator and rotor win dings cause
the rotor to be aligned in line with the stator winding S
2
.
• When the magnitudes of the stator voltages changed, the stator
current also changes. The resultant stator field changes di rection,
causing the rotor field to follow it.
• As the rotor field follows the resultant stator field, the r otor shaft
starts to turn. Rotor motion is tampered by the fly wheel.
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

10. Differentials:
• When the difference in shaft speed between the transmitterand
the receiver is required, we use differential synchro.
• There is hardly any difference between the construction of
synchronous generator and motor and between the differential
generator and motor except that the differential system has three
windingin therotoralso.
• In a differential generator, voltage is applied to the stat or windings.
As the rotor turns, varying voltages are obtained at the rotor
terminals.
• In the differential motor, voltage applied to both rotor an d stator.
The resultant magnetic field decide the position of the roto r.
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

11. Differentials:
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018

12. References:
• Smarajit Ghosh, “Control Systems: Theory And Applications”,
Pearson Education India, 2004.
Control System Components (ICE 3015)
Dr.
S.Meenatchisundaram
, MIT, Manipal, Aug
–
Nov 2018