Research Article Optimization of the Switch Mechanism in a

Research ArticleOptimization of the Switch Mechanism in a Circuit BreakerUsing MBD Based Simulation

Jin-Seok Jang,1 Chang-Gyu Yoon,1 Chi-Young Ryu,2 Hyun-Woo Kim,3

Byung-Tae Bae,3 and Wan-Suk Yoo4

1School of Mechanical Engineering, Pusan National University, Busan 609-735, Republic of Korea2Agency for Defense Development, P.O. Box 126, Changwon, Gyeongnam 641-836, Republic of Korea3Hyosung Corporation, Changwon 641-712, Republic of Korea4Faculty of Mechanical Engineering, Pusan National University, Busan 609-735, Republic of Korea

Correspondence should be addressed to Wan-Suk Yoo; [email protected]

Received 10 October 2014; Accepted 7 January 2015

Academic Editor: Shuhuai Lan

Copyright © 2015 Jin-Seok Jang et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A circuit breaker is widely used to protect electric power system from fault currents or system errors; in particular, the openingmechanism in a circuit breaker is important to protect current overflow in the electric system. In this paper, multibody dynamicmodel of a circuit breaker including switch mechanism was developed including the electromagnetic actuator system. Since theopening mechanism operates sequentially, optimization of the switch mechanism was carried out to improve the current breakingtime. In the optimization process, design parameters were selected from length and shape of each latch, which changes pivot pointsof bearings to shorten the breaking time. To validate optimization results, computational results were compared to physical testswith a high speed camera. Opening time of the optimized mechanism was decreased by 2.3ms, which was proved by experiments.Switch mechanism design process can be improved including contact-latch system by using this process.

1. Introduction

A circuit breaker is widely used to protect electric powersystem from fault currents or system errors. Spring actuatedlinkage system is a reliable mechanical device to transfer thestored elastic energy of the opening and closing spring tothe mechanism composed of cams and links at a high speed.In particular, the opening mechanism is crucial in a circuitbreaker to protect the electric systems under the emergencyof current overflow.

Since the spring-type operation mechanism is composedof cams, several links, and springs, the system is rather com-plex [1]. Computer simulation such as multibody dynamicanalysis had been widely used to analyze these kinds ofmultibody systems. For an advanced design of a circuitbreaker, however, the designer has to estimate the accurateload history reacting on all the moving links and joints forvarious operation conditions. For this reason, a multibodydynamic analysis was necessary to estimate and validate

dynamic characteristic and analyze the operating time. Ahnand Kim [2] applied the lumped parameter spring modelin the vacuum circuit breaker to carry out the dynamicanalysis of the circuit breaker. Pisano and Freudenstein [3]measured the dynamic performance of high speed cam-follower system by experiment. Yoo et al. [4] studied thespring actuated linkage system in circuit breaker systemusing MBD analysis program. Jang et al. [5] researchedthe possibility of cam profile optimization used in a springactuated linkage system. To increase the stem velocity withthe lowest spring force, many links are used in a circuitbreaker. In the previous researches, dynamic analysis of thesystem was mainly focused.

In this paper, dynamic analysis technique was applied todesign the circuit breaking mechanism. To start an optimaldesign, a precise multibody modeling of the circuit breakerwas first developed. After the dynamics simulation withthe developed multibody model, physical experiments werecarried out to verify the simulation. Verifying the simulation

Hindawi Publishing Corporatione Scientific World JournalVolume 2015, Article ID 347047, 7 pageshttp://dx.doi.org/10.1155/2015/347047

2 The Scientific World Journal

Figure 1: A circuit breaker.

results, an optimization process was adopted for the systemto shorten the operating time. Since the switch mechanismhas several contact conditions, such as roller-latch, solenoidplunger-latch, and latch stopper, design parameter is requiredto satisfy the contact condition to keep the closing condi-tion. In this study, design parameters were selected fromeach length and shape of latches and bearing pivot points.Parametric study was first carried out and the optimizationsoftware VisualDOC was employed with dynamics analysisprogram MSC.ADAMS and electromagnetic actuator anal-ysis software AMESim. To validate optimization results, anopening test was carried out with the optimum results. Ahigh speed camera more than 3,000 frames per second wasused to capture the motion and analyze the tracking points.For design of switchmechanism including contact conditionsof several steps, switch mechanism design process can beimproved.

This paper is structured as follows. Section 2 explains thecircuit breaker mechanism and the multibody system mod-eling including the solenoid. Construction of the coupledanalysis system is explained. In Section 3, parameterization ofswitch parts is explained. And Section 4 shows the optimiza-tion procedure and validation results through the experimentusing high speed camera. Finally, summary and conclusionsare drawn in Section 5.

2. Dynamics Model

2.1. Multibody Dynamics Model. Figure 1 shows a circuitbreaker model used in this research, and graphical topologymap of the circuit break system is shown in Figure 2. Eachnumber in circles means body and “S” means a spring ele-ment. Symbols “B,” “C,” “R,” “S,” and “T” mean bushing forceelement, contact force model, revolute joint, spherical joint,and translational joint, respectively. Total system consists of18 bodies, and it has 29 degrees of freedom as shown inTable 1.

Several latch stoppers are connected to groundby bushingelement to represent flexible mount effects and vibrationreduction. Therefore, many DOF appear in this switchmechanism, which have several latches, roller, stopper, andsolenoid. Operation sequence of a switch mechanism incircuit breaker system is explained in Figure 3.

G

2

4

567

8R

3

R

RR

R

9

R

10

1112R

1

R

C

13

14

15

TS

16

17

C

T

S

C

R

R

S1

S1

S2

S3

C2

C2

C2

C2

C2

C2

C1

C1

C2

B1

B1

B1

B1

B1

B1

S4

S5

(9) Impact roller(10) Impact latch(11) Impact latch stopper(12) Open lever(13) Open guide hinge(14) DP rod(15) Open spring guide lever(16) DP hinge(17) Open roller

(6) 3rd latch (7) 3rd latch stopper(8) 1st latch roller

(G) Ground

(2) 1st latch(3) 1st latch stopper(4) 2nd latch(5) 2nd latch roller

(1) SOL MASS

Figure 2: Graphical topology of a circuit breaker.

Table 1: DOF of the system.

Classification DOFBodies 18 ∗ 6 = 108Cylindrical joints 3 ∗ −4 = −12Revolute joints 10 ∗ −5 = −50Spherical joints 2 ∗ −3 = −6Translational joints 2 ∗ −5 = −10Motion 1 ∗ −1 = −1

Total DOF 29

Step 1. When an emergency situation occurs in a circuitbreaker system, the first movement occurs in the plunger of asolenoid.

Step 2. Plunger pushes the 3rd latch and then the 3rd latchstarts to rotate counter clockwise. And then, contact betweenthe 3rd latch and the 2nd latch is released.

Step 3. Releasing the contact with the 3rd latch, the 2nd latchrotates counterclockwise.

Step 4. Releasing the contact with the 2nd latch, the 1st latchrotates counterclockwise.

Step 5. Releasing the contact with the 1st latch, the open leverrotates counterclockwise. Then, the circuit is open, whichmeans the circuit breaker is successfully done.

The Scientific World Journal 3

Step 1

Step 2

Step 3

Step 4

Step 5

3rd latch

Solenoid

2nd latch

1st latch

Open lever1

2

3

Figure 3: Operation sequence of switch parts.

0

2

4

6

8

10

12

Input signal 3rd latch 2nd latch 1st latch Open lever

Tim

e (m

s)

Exp 1

Exp 2 SimulationExp 3

Figure 4: Comparison results between experiments and simulation.

In this study, the operating time starting from Steps 1 to 5was chosen as an objective value since circuit breaker finishesits role. In Figure 3, contact forces at a static equilibriumposition were also drawn.

2.2. Analysis and Validation with the Developed MultibodyModel. Figure 4 shows comparison results between experi-ments and simulation. Each point in Figure 4 means time tomove the latches and open lever. In particular, the time differ-ence between experiments and simulation is within 0.4ms.Since the discrepancy between experiment and simulationwas small, it could be said that the multibody model wasverified.Thus, optimizationwas carried out using this verifiedmultibody dynamics model.

3. Design Optimization

3.1. Selection of Design Variables. In Figure 5, selected designvariables are shown, and their physical meaning was illus-trated in Table 2. In switching part, roller point and pivotpoints of latches are selected as design parameters, in which

Design parameters

OriginLocal.1

Local.3

Local.4

Local.5

Local.2

Design point: revolute joint locationDesign point: roller point

A2

A3

A4L4

A1

L1

L2

L3

X

YJoint coordinates with reference frame

Figure 5: Selection of design parameters.

positions and angles were measured from local referenceframe. In Table 2, upper and lower limits of the designparameters were shown. These limits were considered bylimitation of installation range and manufacturing condi-tions. Five of these parameters such as “𝐴

2,” “𝐴4,” “𝐿2,”

“𝐿3,” and “𝐿

4” were selected for parametric study, which

were judged by an expert designer as main parameters.In the sequential operation from Steps 1 to 5, the contactcondition should be preserved. Therefore these conditionswere considered as boundary limits of design parametersshown in Table 2. Equation (1) explains global position ofroller and pivot points which were named as Local.1, Local.2,Local.3, Local.4, and Local.5. Figure 6 shows configurationsof switch parts when the parameter changes “𝐴

2” and “𝐿

2,”


Local.1

Local.3

Local.4

Local.2

Origin

Local.5

A2A3

A4L4

A1

L1

L2

L3

(a) Original

A2

+

−

(b) Change in 𝐴2

L2

+

−

(c) Change in 𝐿2

Figure 6: Configurations of switch mechanism according to parameter changes.

Table 2: Design parameters and boundary values.

Description Lowerlimits

Upperlimits

Selection criteria forboundary values

𝐴1

Angle (deg) −10 10 Interruption of parts𝐴2

Angle (deg) −30 10 Closing condition𝐴3

Angle (deg) −15 15 Interruption of parts𝐴4

Angle (deg) −30 10 Closing condition𝐿1

Length (mm) −3 3𝐿2

Length (mm) −10 15 Effects on the openingtime and minimum

length𝐿3

Length (mm) −4 4𝐿4

Length (mm) −7 10

representatively. If 𝐴2and 𝐿

2change, global position of

“local.3”, “local.4,” and “local.5” is calculated by using (1).The following method has many advantages, in checkingstatic equilibrium condition for keeping the closing conditionand in analyzing independent characteristics of switch part.Consider

Local.1 = [00

]

Local.2 = Local.1 + [𝐿1sin (𝐴

1)

−𝐿1cos (𝐴

1)

]

Local.3 = Local.2 + [𝐿2cos (𝐴

1+ 𝐴2)

𝐿2sin (𝐴

1+ 𝐴2)

]

Local.4 = Local.3 + [𝐿3cos (𝐴

1+ 𝐴2+ 𝐴3)

𝐿3sin (𝐴

1+ 𝐴2+ 𝐴3)

]

Local.5 = Local.4 + [−𝐿4sin (𝐴

1+ 𝐴2+ 𝐴3+ 𝐴4)

𝐿4cos (𝐴

1+ 𝐴2+ 𝐴3+ 𝐴4)

] .

(1)

3.2. Objective Function in Optimal Design. To shorten thetotal operation time for a circuit breaker, the total time forthe five steps previously mentioned in Section 2.1 should be

0 0.005 0.01 0.015

0

2

4

6

8

Time (s)

Curr

ent (

mA

)

LoadedUnloaded

−2

Figure 7: Current responses between loaded and unloaded condi-tion.

analyzed. Thus, object function was selected the time whenthe open lever is rotated 0.1 degree:

Opening time = Opening lever angle > 0.1∘. (2)

4. Optimization Results and Validation

4.1. Optimization Process. When a circuit breaker detects thefault current or system errors, the opening mechanism in thecircuit breaker starts from the solenoid operation shown inFigure 5. Therefore solenoid model is important to develop amodel for switch mechanism analysis.

In this study, a multibody analysis code MSC.ADAMScalled AMESim program as an external solver to analyze afluid mechanical system and electromagnetic system. First,the solenoid model is developed in the AMESim and calledby external solver in the MSC.ADAMS. Figure 7 shows thecomparison between unloaded case and loaded case applied


VisualDOC

Current solenoid force

Iteration

External solver

Modified D.P.

∙ Results (force and constraints)∙ Object function (opening time)

∙ Static equilibrium condition∙ Contact force

Solenoid model(∗ .dll)

Figure 8: Optimization process of coupled system.

by AMESim. Difference in current shows the necessity toconsider the magnetic interaction in the solenoid becausecurrent applied to solenoid force is different. Figure 8 showsthe coupled system modeling based on MSC.ADAMS andoptimization process on VisualDOC, in which VisualDOCprogram can integrate process and optimization [6, 7]. Staticequilibrium conditions and contact force are estimated forsatisfying the closing condition.Multibody dynamics analysiswas carried out with MSC.ADAMS using the predevelopedsolenoid model in external solver AMESim. Optimizationwas carried out using a genetic algorithm supplied in theVisualDOC. Genetic algorithm searches heuristic that mim-ics the process of natural evolution, and this heuristic isused to generate useful solutions to optimization. Algorithmcondition was chosen for probability of crossover as 1.0,probability of mutation as 0.1, and population size as 100.

4.2. Optimization Results. Table 3 shows optimization resultsof the switch mechanism. In case of the original mecha-nism, opening time was 10.86ms. After the optimal design,the opening time was reduced to 8.16ms. Improvementof 24.8% was obtained with the time reduction of 2.7ms.Figure 9 shows the comparison between the original designand the advanced design after optimization. Table 3 showsoptimization results of the switch mechanism. In case of theoriginal mechanism, opening time was 10.86ms. After theoptimal design, the opening time was reduced to 8.16ms.Improvement of 24.8% was obtained with the time reductionof 2.7ms.

4.3. Experimental Validation. To validate the optimizationresult, experiment of switch mechanism was also carriedout with the design changes. Firstly housing and latches

Table 3: Optimization results.

(a)

Initial value Optimum value𝐿2(mm) 0 15.0𝐿3(mm) 0 −3.5𝐿4(mm) 0 5.0𝐴2(deg) 0 −28.5𝐴4(deg) 0 −28.5

(b)

OptimizationOpening time ofexisting mechanism 10.86ms

Opening time ofoptimal mechanism 8.16ms

Reduced time 2.7msImprovement (%) 24.8Total computing time 3.2 hours

were newly manufactured and assembled. Since the openingprocess is finished with several milliseconds, therefore a highspeed camera was used to capture the motion. Experimentsetup is shown in Figures 10 and 11. Several lights wereused to secure a clear view for high speed camera, and loadcells and indicators were installed in order to conduct thesame condition of spring force. During the motion capturingprocess, an LED lamp was used to check the start time. Thelatchesmotionswere captured in 3000 frames per second, andthen the captured data was converted to position data usingTEMA software [8].

4.4. Validation Results. To get the position data accordingto time, the points of each latch were tracked by markers,which were attached to latches and open lever as shownin Figure 12. Also an LED was also installed to check thestart time as shown in Figure 12. To validate experimentreproducibility, experiments were carried out three timesrepeatedly. In Figure 13, measured times to move the openlever were shown, in which three curves with original modeland other three curves with the optimized design werecompared. Figures 14 and 15 compare displacement of latchesand open lever with original design and the optimizeddesign, respectively. By comparing two figures, optimallydesigned mechanism has faster operation time than theoriginal mechanism. “Input signal” in figures means the timewhen the current was applied. As shown in figures, the 3rdlatch and the 2nd latch start to rotate at 3.3ms and 6ms,respectively. After two latches rotating, in case of optimallydesignedmechanism, responses of the 1st latch are faster thanthe original mechanism about 2.0ms. Start time to rotate theopen lever was decreased by 2.3ms. Since the start time isdifficult to judge as shown in Figures 14 and 15, the timefor the maximum open lever displacement was compared.Judging from the time, the opening time was decreased by2.6ms in experiments. Additionally, the rotation ranges of the


Figure 9: Geometry configuration shapes of existing model and optimal model.

LEDLoad cell

Solenoid

Switchmechanism

Powersupply

Indicator

Parallelconnection

Light(halogen)

Light(halogen)

Light(halogen)

Light(halogen)

Light(LED)

Computer

Motion studio

Raw converter

TEMA (software)

Disk spring

High speedcamera

Resistance(8kΩ)

Resistance(4kΩ)

Figure 10: Diagram of experiments set for switch mechanism by using high speed camera.

3rd and the 2nd latch in the optimally designed mechanismare smaller than those at original mechanism. However, openlever and the 1st latch have the same moving range.

5. Conclusion

Multibody dynamics model of a circuit breaker systemwas developed and the coupled analysis model was devel-oped including electromagnetic actuator. Parameterizationof design variable was carried out, and static equilibriumcondition for the closing station was checked for the designvariables. In the optimization process, the object functionwas

defined tominimize the time for rotating of the open lever 0.1degree.

Optimization was carried out using a genetic algorithmwith the ViualDOC program. As a result, opening time wasdecreased by 2.7ms in simulation. To verify the optimizationresults, experiments were also carried out with the optimaldesign components. For the experimental setup, a highspeed camera was used to capture the motion with severalindicators, load cells, lamps, and LED lamp. Three repetitiveexperiments were carried out for verifying the experimentalreproducibility. The results showed that the opening timewas decreased by 2.3ms.Therefore, switchmechanismdesign


Figure 11: Picture of experimental setup.

1st latch

2nd latch3rd latch

Open lever

Input voltage

Figure 12: Markers in the experimental setup.

0

2

4

6

8

10

12

Input signal 3rd latch 2nd latch 1st latch Open lever

Tim

e (m

s)

Original 1Original 2Original 3

Optimal 1Optimal 2Optimal 3

Figure 13: Times to move the latches and the open lever.

4 6 8 10 12 14 16 18

05

1015

Ang

le (d

eg)

Time (ms)0 2 20

05101520

Disp

lace

men

t (m

m)

3rd latch (ang.)2nd latch (ang.)1st latch (ang.)

Input signalOpen lever (disp.)

−5

18ms14ms

10.7ms

Figure 14: Displacement of latches and open lever (original mech-anism).

0 2 4 6 8 10 12 14 16 18 20

048

Ang

le (d

eg)

Time (ms)

05101520

Disp

lace

men

t (m

m)

−5

15.4ms

8.4ms

11.7ms

3rd latch (ang.)2nd latch (ang.)1st latch (ang.)

Input signalOpen lever (disp.)

Figure 15: Displacement of latches and open lever (optimizedmechanism).

process can be improved including contact-latch system byusing this process.

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper.

Acknowledgment

This work is supported by Hyosung Corporation.

References

[1] K. Y. Ahn and K. Y. Jeong, “Optimization of the spring designparameters of a circuit breaker for satisfying specified dynamiccharacteristics,” Journal of the Korean Society for PrecisionEngineering, vol. 21, no. 3, pp. 132–138, 2004.

[2] K. Y. Ahn and S. H. Kim, “Dynamicmodel and analysis of a vac-uum circuit breaker mechanism for high-speed closing andopening simulations,” Journal of the KSPE, vol. 19, no. 10, pp.132–138, 2002.

[3] A. P. Pisano and F. Freudenstein, “An experimental and ana-lytical investigation of the dynamic response of a high-speedcam-follower system. Part 2: a combined, lumped/distributedparameter dynamic model,” Journal of Mechanical Design, vol.105, no. 4, pp. 699–704, 1983.

[4] W.-S. Yoo, S.-O. Kim, and J.-H. Sohn, “Dynamic analysis anddesign of a high voltage circuit breaker with spring operatingmechanism,” Journal of Mechanical Science and Technology, vol.21, no. 12, pp. 2101–2107, 2007.

[5] J. S. Jang, J. H. Sohn, and W. S. Yoo, “Optimization of the camprofile of a vacuum circuit breaker by using multibody dynam-ics techniques,”Transactions of the Korean Society ofMechanicalEngineers, A, vol. 35, no. 7, pp. 723–728, 2011.

[6] J. K. Ok, Optimum design of a torsion-beam suspension mech-anism using ADAMS and Visual DOC [M.S. thesis], PukyongNational University, Busan, Republic of Korea, 2005.

[7] G. Choi, J. Sohn, H. Kim et al., “Performance improvement of agas-insulated circuit breaker using multibody dynamic simu-lations and experiments,” Journal of Mechanical Science andTechnology, vol. 27, no. 11, pp. 3223–3229, 2013.

[8] TEMA R&D, TEMA User's Guide, 2009.

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Research Article Optimization of the Switch Mechanism in a