The document summarizes the optimization design of a permanent magnet actuator (PMA) for a 126-kV vacuum circuit breaker. It discusses: 1) The structure and working principles of the mono-stable PMA with separated magnetic circuits for holding and driving functions. 2) A multi-step optimization method that divides the design into three modules - breaking spring mechanism, PM holding mechanism, and closing driving mechanism. 3) The optimization results showing improved performance over the initial design, with validation from a physical prototype, helping to reduce costs and extend service life.

1. SEMINAR PRESENTATION
BY
MOHAMMED M
S8 EEE
ROLL NO :36

2. Optimization Design of a Permanent Magnet
Actuator for 126-kV Vacuum Circuit Breaker
2
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 28, NO. 3, MARCH 2018

3. CONTENTS
• Objective
• Introduction
• Topology Structure
• Working principle
• Optimization Design
• Conclusion
• Reference
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4. OBJECTIVE
• To discuss about role PMA used in high voltage power system.
• Multi-step optimization method is applied to decrease the optimization
time and get a global optimal solution.
• Compare the result among optimized design and initial design and
prototype.
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5. INTRODUCTION
• Vacuum circuit breakers (VCBs) have been widely used in the distribution
voltage levels of 3.6∼40.5 kV.
• The vacuum interrupter in VCBs plays a role in quenching arcs and
withstanding recovery voltages through the movement of movable contact,
which is driven by the operating mechanism through an insulating pole.
• PMA used in high-voltage power system has a much longer stroke and requires
a much higher velocity.
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6. •A new bi-stable PMA was proposed in which consists of a holding and a
driving component whose magnetic circuits are separated.
•This PMA exerts a good closing performance, its breaking performance is
unsatisfactory due to coil inductance prevents the rapid growth of the coil
current during the initial phase of breaking operation.
•Mono-stable PMA separated magnetic circuits completes breaking operation
via the breaking spring and the auxiliary breaking coil, by which a fast breaking
requirement can be met.
•Multi step optimization method.
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7. STRUCTURE OF MONO-STABLE PMA
Holding part
• The holding part comprises of a static iron core and movable core for
holding , PM and auxiliary breaking coil, both of which are imbedded
in a static core.
Driving part
• The driving part consists of a static core and movable core for driving,
a closing coil and a disc spring, which is installed between the shell
and the movable core for holding.
• The movable cores in the two parts are fixed on a shaft, through which
the electromagnetic force can be transferred to the movable contacts of
VCB.
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8. Fig 1:Structure of the proposed PMA. (a) Closed state. (b) Open state
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9. Working principle
Closed state
• PMA maintains the closed state by the force generated from the PM in the
holding part.
• The disc spring is under compression when the movable core is at the closed
position.
• auxiliary breaking coil is excited, the air gap magnetic flux density between
the static and the movable cores in the holding part rapidly decreases.
• holding force decreases dramatically with the increase of air gap length
• current in the auxiliary breaking coil increases to a certain value, the movable
core for holding begins to move down
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10. Open state
• The action of spring force exerted on the movable core for holding.
• The auxiliary breaking coil helps rapidly decrease the holding force acting
on the movable core in the holding part.
• The large initial compression force of the spring is able to satisfy the high
velocity requirement for opening operation.
• The combination of auxiliary breaking coil and breaking spring enables the
VCB to acquire a good breaking performance.
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11. Optimization of PMA
• The main parameters of a 126 kV vacuum interrupter and the requirements
for actuator are listed in Table I.
• The parameters of excitation circuits and spring, and dimension parameters
have significant effects on the actuator performance.
• It is difficult and very time-consuming to optimize these variables
simultaneously.
• PMA can be divided into three sub-optimization modules, including the
optimizations of PM holding mechanism, breaking spring mechanism and
closing driving mechanism.
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12. 12
Item Value
Rated voltage (kV) / Rated current (kA) 126 / 3
Rated short-circuit breaking current (kA) 31.5
Rated contact stroke (mm) / Contact connection stroke (mm) 50 / 10
Added external contact force at contact touch point (N) 2400
Added force on closed contacts (N) 3500
Average opening speed (0–30 mm stroke) (m/s)
Average closing speed (30 mm-contact making) (m/s)
3.5 ±
00..33
2.0 ±
MAIN PARAMETERS OF A 126 KV VACUUM INTERRUPTER AND THE
REQUIREMENTS FOR ACTUATOR

13. 13

14. A . Optimization of Breaking Spring mechanism
• The breaking operation of the proposed PMA is mainly completed by the
breaking spring.
• the parameters of breaking spring, including initial pressure and stiffness.
• The average velocity in 30 mm since contacts separating should be controlled
within a certain range, which is critical to successful breaking
• low terminal velocity of the breaking operation should also be controlled to
decrease the impact and extend the service life.
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15. • where a and b represent the initial
pressure and the stiffness of the
breaking spring, respectively;
• vend(a, b) denotes the terminal velocity
and vav(a, b) denotes the average
velocity.
s.
3.2 m/s ≤ Vav(a,b) ≤ 3.8 m/s
Fig 2:Optimization process curve of GA for the breaking spring.
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16. B. Optimization of PM Holding Mechanism
• Since the PM holding mechanism functions as keeping the movable contacts in
closed state steadily.
• The mechanism should provide a holding force larger than the anti-force at the
closed position.
• The volume of PM should be as small as possible to reduce the cost.
• The three main design variables r, LM, hM ,These three variables denote the
inner radius of PM, the thickness of PM and the height of PM
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17. Fig.3: Optimization of PM holding mechanism.
(a)Design variables
(b) Optimization process curve of GA for the PM holding
mechanism
2 mm ≤ LM ≤ 20 mm,
10 mm ≤ hM ≤ 60 mm
55 mm ≤ r ≤ 200 mm
VPM(LM, hM, r) is the volume of the PM,
Fhold(LM, hM, r) is the holding force produced by PM
at the closed position
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18. C . Optimization of Closing Driving Mechanism
• Closing driving mechanism consists of a mechanical part and an excitation
circuit part.
• The variation of parameters in these two parts will lead to the change of
closing dynamic characteristics.
• The average velocity in 30 mm before contacts closing plays a key role in
successful closing.
• 1.7 m/s ≤ Vav ≤ 2.3 m/s
• Terminal velocity of the closing operation should be as low as reasonable to
reduce the bouncing time and the wear of contacts.
• The excitation circuit parameters, including initial voltage of capacitor Uc,
capacitance C and coil turns N, are optimized.
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19. Fig 4: Equivalent excitation circuit for closing coil
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20. D. Optimization results and experimental verification
• The optimized PMA satisfies all the requirements for actuator, including the
PM holding force, breaking and closing average velocities.
• the optimized PMA requires smaller amount of PM and the terminal
velocities of both breaking and closing operations are much lower, which
helps reduce the cost and extend the service life.
• A slight error exists mainly because of the mechanical factors such as friction
force, spring load etc.
• The vibration at the end of the processes caused by collision is not taken into
account.
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21. Fig 5: Experimental platform. (a) Prototype. (b) Control and drive circuits.
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22. 22
Items Initial design Optimized design Prototype
PM holding force (N) 14240 17867 16927
PM volume (mm3) 101940 52474 52474
Average velocity of opening (m/s) 2.70 3.2 3.5
Terminal velocity of opening (m/s) 3.63 4.37 4.81
Average velocity of closing (m/s) 2.39 2.11 2.03
Terminal velocity of closing (m/s) 2.82 0.61 0.67
Peak current during closing (A) 68.1 87.5 92.5
COMPARISON OF RESULTS AND PERFORMANCE

23. CONCLUSION
• A new mono-stable PMA with separated magnetic circuits has been
proposed for 126 kV VCB.
• A multi-step optimization method was adopted and the whole optimization
was divided into three parts, namely the optimizations of breaking spring
mechanism, PM holding mechanism and closing driving mechanism.
• The usage amount of the PM and the terminal velocities of opening and
closing operations are reduced compared to the initial model.
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24. REFERENCE
• P. G. Slade, The Vacuum Interrupter: Theory, Design, and Application. Cleveland, OH,
USA: CRC Press, 2008, pp. 1–2.
• Z. X. Wang, P. Yan, Y. S. Geng, and L. Yu, “Simulation of an improved operating method
for vacuum circuit breakers with permanent magnetic actuators,” Int. J. Appl. Electromagn.
Mech., vol. 33, no. 3–4, pp. 1373–1381, 2010.
• Z. X. Wang, L. Sun, S. He, Y. Geng, and Z. Liu, “A permanent magnetic actuator for 126
kV vacuum circuit breakers,” IEEE Trans. Magn., vol. 50, no. 3, pp. 129–135, Mar. 2014.
• H. Saitoh et al., “Research and development on 145 kV/40 kA one break vacuum circuit
breaker,” in Proc. IEEE/PES Transmiss. Distrib. Conf. Exhib., 2002, pp. 1465–1468.
• B. A. R. Mckean, “Magnets and vacuum-the perfect match [MV distribution switchgear],”
in Proc. 5th Int. Conf. Trends Distrib. Switchgear, 400 V-145 kV Utilities Private Netw.,
Nov. 1998, pp. 73–79.
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25. • J. H. Kang, C. Y. Bae, and H. K. Jung, “Dynamic behavior analysis of permanent
magnetic actuator in vacuum circuit breaker,” in Proc. 6th Int. Conf. Elect. Mach. Syst.,
2003, pp. 100–103.
• S. Fang, H. Lin, and S. Ho, “Transient co-simulation of low voltage circuit breaker with
permanent magnet actuator,” IEEE Trans. Magn., vol. 45, no. 3, pp. 1242–1245, Feb.
2009.
• Z. Y. Cai, S. H. Ma, and J. M. Wang, “An approach of improve permanent magnetic
actuator of vacuum circuit breaker,” in Proc. 23rd Int. Symp. Discharges Elect. Insul. Vac.,
2008, pp. 165–168.
• Z. X. Wang, P. Yan, Y. S. Geng, and L. Yu, “Simulation of an improved operating method
for vacuum circuit breakers with permanent magnetic actuators,” Int. J. Appl.
Electromagn. Mech., vol. 33, no. 3–4, pp. 1373–1381, 2010.
• J. S. Ro, S. K. Hong, and H. K. Jung, “Characteristic analysis and design of a novel
permanent magnetic actuator for a vacuum circuit breaker,” IET Elect. Power Appl., vol. 7,
no. 2, pp. 87–96, Feb. 2013.
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26. THANK YOU
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