performance improvement of a gas-insulated circuit breaker using multibody dynamic simulations and...

Journal of Mechanical Science and Technology 27 (11) (2013) 3223~3229

www.springerlink.com/content/1738-494x DOI 10.1007/s12206-013-0845-9

Performance improvement of a gas-insulated circuit breaker

using multibody dynamic simulations and experiments† Gyuseok Choi1, Jeonghyun Sohn1,*, Hyunwoo Kim2, Wansuk Yoo2, Byungtae Bae3,

Jaeyeol Kim3 and Jinho Kim3 1Department of Mechanical & Automotive Engineering, Pukyong National Univ., Busan,608-739, Korea

2Department of Mechanical Engineering, Pusan National Univ., Busan, 609-735, Korea 3Switchgear research team, Power & Industrial System R&D Center of Hyosung Corporation, Changwon, Korea

(Manuscript Received December 12, 2012; Revised April 28, 2013; Accepted May 27, 2013)

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Abstract The operating performance, spring characteristics, and material properties of a gas-insulated circuit breaker were optimized using mul-

tibody dynamics. The circuit breaker consisted of several latches and a cam. The dynamic behavior of the latches was affected by the spring characteristics, as well as by the materials and length of each latch. Our results indicated that the motion of the latches was a key factor in determining the opening time of the circuit breaker. A multibody model for the circuit breaker was developed and verified by comparing simulated results with experimental data. The opening time for the breaker was reduced by 1.5 ms in simulations.

Keywords: Circuit breaker; Operating mechanism; Matching technology; Performance improvement; Multi-body dynamics ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction

The opening and closing characteristics of an electric contact in a circuit breaker depend on a high-speed mechanism consist-ing of a cam and a spring-actuated latch system. The spring-actuated latch system is a simple, reliable device used to move heavy loads at high speeds and accelerations. Such a mecha-nism is used in a circuit breaker to complete the switching ac-tion within several tens of milliseconds. Thus, systematic stud-ies on the spring-actuated latch system are required to improve circuit breaker performance. The opening time is one of the key parameters in the kinematic design of circuit breakers.

There have been several studies on how to improve circuit breaker performance. Ann [1, 2] applied the lumped-parameter spring model to vacuum circuit breakers to deter-mine the optimum positioning. Pisano [3] studied the dynamic performance of a high-speed cam-follower system. Yoo [4] determined the spring force of the operating mechanism using multibody dynamic (MBD) analysis. In these studies, most of the mechanisms were composed of several parts, joints and a cam. Most of the parts were connected using revolute or trans-lational joints and the analysis and optimum design process were slightly easier compared with a multi-contact problem.

In this study, however, we considered a more complex

mechanism to model a gas-insulated circuit breaker, in which the operating mechanism included several contact elements, a cam, and spring elements instead of joints. Therefore, the abil-ity to obtain good agreement between simulations and ex-periments was difficult compared with previous studies. We used the MBD technique to model the dynamics of the gas circuit breaker. The commercial software package Adams was used for the modeling and simulation. Optimal design was carried out using VisualDOC and a genetic algorithm. The performance results for the circuit breaker were improved by using the optimum design configuration to adjust the lengths of the latches as well as the spring characteristics through an iterative simulation and optimization procedure.

A dynamic model for the circuit breaker was established and verified by comparing the simulation results with those obtained from experiments. A high-speed camera captured the motion of the latch. The important design variables were iden-tified using sensitivity analysis. The opening time for the op-timum design was reduced by 1.5ms. Additional testing was used to verify the optimal design.

2. Dynamic analysis method for multi-body systems

The Hilber-Hughes-Taylor method (HHT) [5] is widely used in the structural dynamics community for the numerical integration of a linear set of second ordinary differential equa-tions (ODEs). A precursor of the HHT method is the New-mark method, in which a family of integration formulas de-

*Corresponding author. Tel.: +82 51 629 6166, Fax.: +82 51 629 6150 E-mail address: [email protected]

† Recommended by Editor Yeon June Kang © KSME & Springer 2013

3224 G. Choi et al. / Journal of Mechanical Science and Technology 27 (11) (2013) 3223~3229

pends on two parameters β and γ, defined by Eqs. (1) and (2):

( )2. .. ..

1 11 2 22n n n n nhq q hq q qb b+ +é ù= + + - +ê úë û

(1)

( ). . .. ..

1 11 .n n n nq q h q qg g+ +é ù= + - +ê úë û

(2)

The HHT method possesses stability and ordered properties,

provided [ 1/ 3, 0] .a Î - Parameters β and γ are defined as shown in Eq. (3):

1 22ag -

= and ( )21.

4a

b-

= (3)

In constrained mechanical systems, the connecting joints re-

strict the relative motion of the bodies and impose constraints on the generalized coordinates. The kinematic constraints are formulated as algebraic expressions, as shown in Eq. (4), in which generalized coordinates are used [6]:

( ) ( ) ( )1, , , 0.T

mq t q t q té ùF = F F =ë ûL (4)

In Eq. (4), m is the total number of independent constraint

equations that must be satisfied by the generalized coordinates throughout the simulation. Differentiating Eq. (4) with respect to time leads to the constraint relationship between the veloci-ties in Eq. (5):

( ) ( ), , 0q tq t q q tF +F =& .iq

j

é ù¶FF = ê ú

¶Fê úë û (5)

The over-dot denotes differentiation with respect to time;

the subscript denotes partial differentiation for 1 ,i m£ £ 1 .j p£ £ Eq. (6) shows the acceleration relationship of the kinematic constraints, obtained by differentiating Eq. (5) with respect to time:

( ) ( )( ) ( ) ( ), , 2 , , 0.q q qt ttqq t q q t q q q t q q tF + F + F +F =&& & & & (6)

The time evolution of the system is governed by the La-

grange multiplier technique of the constrained equations, as shown in Eq. (7):

( ) ( ) ( ), ,T

qM q q q Q q q tl+ F =&& & (7)

where ( ) p pM q R ´Î is the generalized mass; ( , , )Q q q t& pRÎ is the action (as opposed to the reaction ( )T

q q lF ) on the generalized coordinates, pq RÎ and mRl Î is the La-grange multiplier associated with the kinematic constraints.

The iterative Newton-Raphson method requires construct-ing and solving a system of equations, Eq. (8) in this case, for k iterations, where D indicates the Newton differences. The

matrix M and e1 and e2 are defined by Eqs. (9)-(11), respec-tively.

( )( )

1

2

ˆ

0

kkTq

q

eqMel

é ù -é ùé ùF=ê ú ê úê ú -Fê ú ë û ë ûë û

&& (8)

( )

( ) ( )

11

2

1ˆ1

11

n

Tqq q

e QM Mq hq q

QMq hq

ga

l ba

+

¶ ¶= = -¶ + ¶

é ù¶+ + F -ê ú+ ¶ë û

&&&& &

&&

(9)

( ) ( ) ( )1 1 1

11 1

T Tq qn n n

e Mq Q Qal la a+ +

= + F - - F -+ +

&& (10)

( )2 2

1 , .e q thb

= F (11)

3. Multibody model for a circuit breaker

The opening and closing characteristics of the electric con-tact in a gas-insulated circuit breaker use three latches and a cam; a solenoid pushes the third latch to initiate opening of the circuit breaker. Fig. 1 shows the operating mechanism of the circuit breaker, and Fig. 2 shows the directions of the latch motion and contact force. The opening procedure is as follows. The closed state of the electric contact is maintained by each latch. A compressed opening spring stores a large amount of elastic energy, which is released when the breaker opens. The third latch is first pushed by the solenoid. Just after the third latch moves, the second latch rotates. In turn, the movement of the second latch rotates the first latch by contact force. As a result, the open lever is rotated at high speed due to the large amount of stored elastic energy.

The MBD model of the circuit breaker was established us-ing the MSC/Adams program. Each part of the breaker was

Fig. 1. Operating mechanism of the circuit breaker.

Fig. 2. Direction of the latch motion and contact force.

G. Choi et al. / Journal of Mechanical Science and Technology 27 (11) (2013) 3223~3229 3225

considered as a rigid body in this study. Fig. 3 shows a kine-matic diagram of the multibody model. In total, there were 24 joints: four cylindrical joints, ten revolute joints, three spheri-cal joints, three translational joints and four fixed joints. The circuit breaker consisted of three slider-crank mechanisms, which included one cylindrical joint, one revolute joint and one translational joint. Table 1 provides the degrees of free-dom (DOF) of the circuit breaker. The total number of DOF for the circuit breaker was 12. Five compressed springs were used in this model, and the cam drive motion was simulated.

4. Matching simulations with experiments

4.1 Experimental set up

Because the operating mechanism of the circuit breaker moves within several milliseconds, a high-speed camera was used to measure the motion of the linkage at a rate of 1,000 frames per second. Fig. 4 shows the measurement points. Fig. 5 shows these targeted points in more detail. The surrounding support frame and cover plate of the circuit breaker prevented good visibility of the behavior of each latch; thus, the motion of the latches within the cover plate could not be measured in this study. Instead, the moving time of the latch in the hole was captured.

4.2 Comparison with simulations

Figs. 6-8 show the rotation angle of each latch. In this study, the operating start time was compared. The simulation oper-ated at a rate of 1,000 and 10,000 frames per second. The mo-

tion of the third latch was captured 4.5 ms after the initiation of the solenoid movement in the simulation. The second latch moved 1.7 ms after the third latch, and the first latch was acti-vated 4.5 ms after the second latch.

Table 2 gives the differences between the experiments and simulations; only a slight difference was evident (~1 ms). The simulation results indicated faster response times than the experimental values due to link modeling. Because each link and joint was modeled as an ideal connection in the simulation, it could not account for joint clearance and related time loss.

In this study, the force data obtained from AMESim soft-ware was applied to the third latch in the form of a data curve,

Table 1. The degrees of freedom of a circuit breaker.

Body and Joint

22 Bodies * coordinate/body 132

10 Revolute * constraints/joint -50

4 Cylindrical * constraints/joint -16

3 Spherical * constraints/joint -9

3 Translational * constraints/joint -15

4 Fixed * constraints/joint -24

1 Motion * constraints/joint -1

1 Ground * constraints/joint -6

Total degrees of freedom = 11

Fig. 3. Kinematic diagram of a circuit breaker.

Fig. 4. Experimental setup and measuring points.

(a) Second latch (b) Third latch

(c) Open lever

Fig. 5. Measurement points.


shown in Fig. 9. To consider the friction force of the links, the friction diagram shown in Fig. 10, obtained from experiments, was used in this study.

5. Sensitivity analysis

5.1 Sensitivity analysis according to the mass property

Because the latch mass affects the dynamic behavior of the operating system and opening time, an effect analysis of each latch’s mass was carried out. Table 3 shows the opening time

according to the change in mass of each latch. From the sensi-tivity analysis, the mass of the second latch had a larger effect than that of the third latch.

5.2 Sensitivity analysis according to spring length

Table 4 shows the opening time according to the change in the spring length. The opening velocity of the circuit breaker increased with decreasing spring length.

5.3 Sensitivity analysis according to center position of the

second latch’s roller

A sensitivity analysis was performed to determine the major variables that affected the performance of the system. The design variables considered were the spring forces of each latch and the center point of the second latch roller. Fig. 11

Table 3. Operating time according to the mass change.

Mass ratio Mass(kg) Time(ms)

3 0.367 +0.6

2 0.244 +0.3

Original 0.122 0

1/2 0.0612 -0.02

Third latch

1/3 0.0408 -0.02

3 0.798 +1.2

2 0.532 +0.7

Original 0.266 0

1/2 0.133 -0.4

Second latch

1/3 0.088 -0.5

Fig. 9. Solenoid force data.

Fig. 10. Friction force of link.

Table 2. Comparison of operating start time between experiments and simulations.

Body Differences(ms)

Second latch +0.9

First latch +1.1

Open lever +1.1

Fig. 6. Rotation angle of the second latch.

Fig. 7. Rotation angle of the first latch.

Fig. 8. Rotation angle of the open lever.


shows the design variables for the sensitivity analysis. Figs. 12 and 13 show the comparison of opening time

according to the angle and displacement change of the center position of the second latch roller, respectively. From the sen-sitivity analysis, it is noted that the center point of the second latch roller mainly affected the opening time of the circuit breaker.

5.4 Comparisons of sensitivity analysis with experiments

To verify the sensitivity analysis results, several tests were performed based on the change in the spring length. Table 5 compares the opening times of the simulations and experi-ments. The simulation results were in good agreement with the experimental data: only a slight difference was observed in the solenoid’s behavior.

6. Optimal design for reducing the opening time

The optimal design was tested using Adams and Visual-DOC, which could be connected to MSC/Adams through ASCII code. Fig. 14 shows the flow chart for the optimization process. VisualDOC used Adams input data (e.g., *.cmd and *.sub) and output data (e.g., *.out and *.txt) to carry out the optimization process iteratively until the optimum results were achieved.

Genetic algorithms (GAs) were used for this optimum study. A GA is a search heuristic that mimics the process of natural evolution. This heuristic is used to generate useful solutions to optimization and search problems.

The objective function was chosen to minimize the opening time during the opening process of the circuit breaker. The opening time is the time from the initiation of solenoid opera-

Table 5. Comparison of opening time between simulations and ex-periments according to spring length change.

Case Description Simulation Experiment

1 Third latch spring, length reduction of 10 mm 0.3 ms 0.5 ms

2 Second latch spring, length reduction of 8 mm 0.2 ms 0.2 ms

3

Second latch spring reduction 8 mm + third latch spring Reduction 10 mm

0.5 ms 0.7 ms

Fig. 12. Effect of opening time according to angle change.

Fig. 13. Effect of opening time according to displacement change.

Table 4. Opening time according to the change in the spring length.

Spring length

Time (ms)

Spring length

Time (ms)

40 -0.3 52 -0.2

42 -0.2 54 -0.2

44 -0.1 56 -0.1

46 -0.1 58 0

48 -0.1 60 original 0

50 original 0 62 +0.1

52 +0.1 64 +0.2

54 +0.2 66 +0.3

Third latch

56 +0.3

Second latch

68 +0.3

Fig. 11. Design variables for the sensitivity analysis.


tion to the stroke completion at a specific location. When the desired value is reached in the simulation, the sensor function stops the simulation.

Objective function = Min [Time]. A particular design variable was first selected. For this

study, angle and displacement were selected first to determine the parametric modeling of the second and third latches. Sec-ond, the third and second latch spring lengths were re-selected to determine the force variables for the optimal opening time of the circuit breaker. The design variables and bound limits used in this study are given in Table 6.

The constraint function depended on the contact force be-tween the solenoid and the third latch. Opening was initiated by contact between the solenoid and the third latch. However, on occasion, opening of the circuit breaker was generated without contact; the bounds of the contact force, described below, prevented this phenomenon:

-1,400 < Contact force < -300. Table 7 shows the results from the optimal design. From

Table 6, we noted that the spring length was reduced and the radial displacement was moved by −2.3 mm from its initial position. Consequently, the length of the third latch was short-ened slightly. The optimum design configuration was used to adjust the lengths of the latches, as well as the spring charac-teristics. Fig. 15 shows modified parametric modeling of the second and third latches. Based on the simulation, the opening time of the circuit breaker was reduced by 1.5 ms. The latch mass was not included in the design variable list because the mass changed with respect to the center position of the second latch’s roller.

7. Conclusions

The operating performance, spring characteristics, and ma-

terial properties of a gas-insulated circuit breaker were opti-mized using multibody dynamics. The commercial Adams software package was used for the modeling and simulation. Optimal design was carried out using the VisualDOC program and a genetic algorithm. A high-speed camera captured the motion of the latches in the breaker. Through sensitivity analysis, the spring lengths of the second and third latches and the contact position between the second and third latches were determined to be the main factors affecting the dynamic be-havior of the circuit breaker. The performance results for the circuit breaker were improved using the optimum design con-figuration to adjust the lengths of the latches, as well as the spring characteristics, through iterative simulation and optimi-zation. As a result, the opening time of the circuit breaker was reduced significantly by 1.5 ms.

Acknowledgement

This research was supported by Hyosung Corporation.

Fig. 14. Flow chart for optimization process.

Table 6. Limits on design variables.

Design variable Low bound Initial value Upper bound

Angle -10 0 15

Displacement -10 0 15

Third latch spring length 40 50 60

Second latch spring length 52 60 68

Table 7. Result from the optimal design.

Design variable Low bound Initial value Optimum

value Upper bound

Angle -10 0 14 15

Displacement -10 0 -2.3 15

Third latch spring length 40 50 45.9 60

Second latch spring length 52 60 54.4 68

Fig. 15. Modified parametric modeling of the second and third latch.


References

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[4] W. S. Yoo and S. O. Kim, Dynamic analysis and design of a high voltage circuit breaker with spring operating mecha-nism, Journal of Mechanical Science and Technology, 21 (12) (2007) 2101-2107.

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Gyu-Seok Choi is a general manager of switchgear research team at Pukyong National University. His interests are in kinematic design and dynamic analysis of mechanical system.

Jeong-Hyun Sohn is an associate pro-fessor in Mechanical & Automotive Engineering at Pukyong National Uni-versity since 2003. His interests are in multi-body system dynamics, mecha-nism design.

Hyun-Woo Kim received his B.S. from Pusan National University (2005), M.S. from Pusan National University (2007). And he is currently a Ph.D. student at Pusan National University. His major area is flexible multi-body dynamics.

Wan-Suk Yoo received his B.S. from Seoul National University (1976), M.S. from KAIST (1978) and Ph.D. from University of Iowa (1985). He is cur-rently a Professor at the School of Me-chanical Engineering at Pusan National University.

Byung-Tae Bae is a principal researcher on the switchgear research team at Hyo-sung Power & Industrial System R&D Center. His interests are in kinematic design and dynamic analysis of me-chanical system.

Jin-Ho Kim is a general manager of the switchgear research team at Hyosung Power & Industrial System R&D Center. His interests are in switchgear design and analysis of electric power system.

Jae-Yeol Kim is a researcher on the switchgear research team at Hyosung Power & Industrial System R&D Center. His interests are in multibody dynamics and flexible multibody dynamics.

performance improvement of a gas-insulated circuit breaker using multibody dynamic simulations and...

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