Special Issue Article Design of permanent magnet motor actuator used in 550 kV gas-insulated switchgear disconnector Advances in Mechanical Engineering 1–9 Ó The Author(s) 2015 DOI: 10.1177/1687814015575428 aime.sagepub.com Kejian Shi, Xin Lin and Jianyuan Xu Abstract To improve the operating characteristics of disconnector, a limited rotating angle permanent magnet motor actuator is presented in this article The mathematical relationship between the moving contact stroke and rotation angle of motor is obtained by analyzing the dynamical coordination characteristics of motor actuator used in 550 kV gas-insulated switchgear disconnector The electromagnetic field equation of motor, motive equation of rotor, and circuit equation of winding are solved simultaneously for acquiring dynamical characteristics of motor The electromagnetic-mechanical coupled calculating model of motor is established by finite element method, and magnetic saturation of stator tooth is calculated and analyzed According to the operating principle of motor, the double-closed control system which collects the motor speed and contact stroke signal during the operation of disconnector is developed The experimental results show that the opening and closing speeds of disconnector are 1.1 and 1.2 m/s, respectively, which meet design requirements The speed-regulating operation of disconnector is also carried out so that the switching speed of disconnector can adjust by motor actuator and control system Keywords Disconnector, limited rotating angle permanent magnet motor actuator, finite element method, magnetic saturation, double-closed control system Date received: November 2014; accepted: 28 January 2015 Academic Editor: Jiu Dun Yan Introduction Very fast transient overvoltage (VFTO) with steep wave-front and high amplitude is generated during switching of disconnector in gas-insulated switchgear (GIS) with no-load short bus bar This transient voltage causes high threat on the insulation of GIS and electronic devices connected to GIS enclosure.1–4 One of the important influential factors of VFTO is the switching speed of the disconnector The research on suppressing VFTO by adjusting switching speed is carried out, and there are still different opinions on this factor Szewczyk et al presented this opinion that increasing the switching speed of the disconnector can shorten the operation time and decrease the number of strikes during the operation Thus, the probability of VFTO is decreased But Yinbiao et al presented the opinion that decreasing the switching speed can decrease the trapped charge voltage and reduce the amplitude of VFTO.5–7 The switching speed of the disconnector mainly depends on the performance of its actuator So far, the School of Electrical Engineering, Shenyang University of Technology, Shenyang, China Corresponding author: Kejian Shi, School of Electrical Engineering, Shenyang University of Technology, Shenyang, Liaoning 110870, China Email: kejian75277@163.com Creative Commons CC-BY: This article is distributed under the terms of the Creative Commons Attribution 3.0 License (http://www.creativecommons.org/licenses/by/3.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (http://www.uk.sagepub.com/aboutus/ openaccess.htm) Downloaded from ade.sagepub.com by guest on October 22, 2015 Advances in Mechanical Engineering actuator of GIS disconnector mainly included spring mechanism, hydraulic mechanism, and electromagnetic mechanism A new type actuator of disconnector is presented, where the spring is used as an energy-storage element to provide driving force during opening and closing operation of the disconnector, and it also simplifies the switching procedure of the disconnector.8 The dynamic simulation and mechanical experiment are carried out for researching electric actuator which applies to 252–1100 kV GIS disconnector and earthing switch.9 In order to further achieve intelligent operation of disconnector, the investigation on the possibility of varying speed operation was performed, and the actuator that can switch with different speeds is developed, but those speeds call for setting forehand.10 The above actuators are not able to adjust the switching speed in real time during opening and closing operation of the disconnector; therefore, the technological development of suppressing VFTO by adjusting switching speed is limited largely A novel permanent magnet (PM) motor as actuator of disconnector is presented in this article First, the analysis of dynamical coordination characteristics of motor actuator used in disconnector is carried out for obtaining the relationship between shaft’s angle of motor and contact stroke of disconnector The operating characteristics of motor during opening and closing operation of the disconnector are simulated The magnetic saturation of motor tooth is taken into consideration in the simulation According to the operating principle of this motor, speed-regulating control system is developed and then the experiment of 550 kV GIS disconnector and motor actuator is carried out The results show that the switching speed of disconnector can adjust by motor actuator under the premise that the speed can meet the performance requirement of disconnector Design of motor and control system u = ua À 408 > > > BAD > AD = AB cosðuBAD Þ > > > > < BD = AB sinðuBAD Þ BE = AF À AD pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi > > À BE2 > CE = BC > > > > CF = CE + BD > : CC0 = CF À C0 F where ua is the rotated angle of motor The rotated angle of motor is 57.1° and 22.9° in clearance between open contacts and over-stroke stage, respectively, and the relationship between rotated angle of motor and contact stroke is shown in Figure The open position, the instantaneous closing (opening) position, and the closed position of disconnector are marked by A, B, and C in this figure, respectively The contact stroke of disconnector is 230 mm and corresponding rotated angle of motor is 80° during opening and closing operation Design and dynamic simulation of the motor Because the motor is regarded as axial symmetric structure, magnetic vector potential A has only z component The two-dimensional magnetic field analysis of motor is necessary In order to simplify the simulated process, assumptions are given as follows:11–13 The electromagnetic field of the motor is regarded as quasi-static field The end effect of the motor is included by end leakage inductance from circuit equation The influence of eddy-current effect is neglected The electromagnetic field equations of the motor are > ∂A > Á > < m1 ∂n Analysis of dynamical coordination characteristics of motor actuator used in disconnector The structure of disconnector transmission mechanism is shown in Figure In this figure, the initial and final positions of operation are marked by AB0C0 and AB1C1, respectively The positional relationship between transmission parts of disconnector is expressed in equation (1) GÀ À m1 Á ∂A ∂n Aj G1 = > > > : ∂ Á ∂A + ∂x m ∂x The whole structure of 550 kV GIS disconnector and its mechanical connection with motor actuator are shown in Figure This system diagram mainly included three parts, namely, disconnector, driving motor, and control system ð1Þ ∂ ∂y m1 G 2+ = JS Á ∂A ∂y = À aa JZa À ab JZb À ac JZc ð2Þ where JS is the current density of PM surface; aa, ab, and ac are the current facts of three-phase windings, respectively; G1 is the stator outer boundary; G2 is the boundary of PM; JZa, JZb, and JZc are the current densities in the z-axis direction of three-phase windings, respectively; and m1 and m2 are the relative permeabilities of motor air gap and PM, respectively The circuit equation of the motor windings is ½U = ½ E + ½ R½ I + ½ L d½ I dt ð3Þ where [U] is the voltage vector, [E] is the electromotive force voltage vector, [R] is the resistor matrix of Downloaded from ade.sagepub.com by guest on October 22, 2015 Shi et al V Moving contact Static contact Connecting lever Connecting shaft Swing lever Motor shaft V Driving Motor Pull bars Limit hoding device Control system A B C Photoelectric encoder Figure System diagram of 550 kV GIS disconnector and motor actuator F B0 C0 C E Insulating tension pole Moving contact C1 D B Connecting lever B1 80° A Rotated spindle Figure Structure of disconnector transmission windings, [I] is the current vector, and [L] is the leakage inductance of windings end The current density of three-phase windings is defined as JZk = N0 ak ik , aSb k = a, b, c ð4Þ where N0 is the number of single windings; a is the number of parallel branches; Sb is the sectional area of single winding; and ia, ib, and ic are the currents of three-phase windings, respectively The induced electromotive force of windings is 1 q nm Dm Am + Am + Am i j k d @2pLef N0 X X A ei = À dt aSb m=1 where p is the number of pole-pairs, Lef is the effective length of armature, nm is the total number of elements in the computational domain, q is the number of slots per pole per phase, Dm is the area of single element, and Am t (t = i, j, k) is the magnetic vector potential of single element The motive equation of the motor is J dO = Tem À TL À RO O dt ð6Þ where J is the equivalent moment of inertia in motor spindle side, O is the angular velocity of motor rotor, Tem is the electromagnetic torque of motor, TL is the load torque, and RO is the drag coefficient The equation of electromagnetic torque is ð5Þ Downloaded from ade.sagepub.com by guest on October 22, 2015 Tem = ia ea + ib eb + ic ec O ð7Þ Advances in Mechanical Engineering 90 C 80 70 $QDJOH(°) B Closing operation 60 50 Opening operation 40 30 20 10 A -10 30 60 90 120 150 80 10 40 Contact stroke(mm) Figure Relationship between rotated angle of motor and contact stroke Stator Table Motor parameter Rotor A phase B phase Motor shaft C phase Photoelectric encoder Figure Structure of the motor The rotated angle can be expressed as dua =O dt ð8Þ The electromagnetic torque is calculated by the Maxwell stress method Lef Tem = m0 2p ð r2 Brn Bun dua ð9Þ where r is the radius of air gap; Brn and Bun are the radial and tangential components of air gap flux density, respectively; and m0 is the permeability of vacuum The discrete equations that describe dynamic characteristics of the motor can be obtained using weighted integral method and coupling equation (3) The dynamic characteristics of the motor are calculated by Parameter Value Shaft radius (mm) Outer stator radius (mm) Inter stator radius (mm) Stator axial length (mm) Wire diameter (mm) Rotated angle (°) 44 170 107 270 1.5 80 solving above equations by Newton–Raphson and combining equation (6).14,15 The structure and major parameters of the motor are shown in Figure and Table 1, respectively To ensure stable operation of GIS disconnector, the two-way PM limiting and keeping device installed at the end of motor is developed, and its main structure is shown in Figure The limiting armature is kept by the suction which comes from the two-way PM when the moving contact of disconnector is in closing and opening positions In order to ensure reliable operation of disconnector, the design suction is 100°N m probably The magnetic field distribution and air gap flux density of the motor as shown in Figures and 7, respectively, are obtained by the finite element method (FEM) calculation The magnetic saturation as a key feature for dynamic analysis of the motor is taken into consideration in the simulation From Figure 6, the Downloaded from ade.sagepub.com by guest on October 22, 2015 Shi et al Permanent magnet Motor shaft Limiting armature Figure The structure of permanent magnet limiting and keeping device magnetic flux density of stator tooth in no-load and max-current modes are 1.6 and 1.8 T, respectively, which reflect that the motor has been worked in nonsaturated status according to B-H curve of stator material (silicon steel sheet: DW470) From Figure 7, the air flux density of motor is approximately rectangular wave in no-current mode; however, the distortion of this wave appeared in maxcurrent mode due to torque ripple and armature reaction The average air flux densities of the motor in these modes are more than T that meet the design requirements of the motor The dynamic characteristics of the motor used in disconnector are obtained by numerical simulation as shown in Figure The opening and closing operation times are 230 and 260 ms, respectively, and the contact stroke is 230 mm According to the technical parameter of 550 kV GIS disconnector, the opening speed is the average speed in three-fourths stroke after instantaneous opening position, and the closing speed is the average speed in threefourths stroke before instantaneous closing position After the calculation, the opening and closing speeds are 1.1 and 1.2 m/s, respectively, that meet the performance requirement of 550 kV GIS disconnector Figure Magnetic field distribution of the motor: (a) no-load mode and (b) max-current mode Design of control system According to the mechanical requirements of disconnector and operating characteristics of the motor, the speed-regulating control system based on TMS320F28335 is developed, and its system structure is shown in Figure The main parts of this control system are introduced as follows: Current detection unit The hall current sensor CHF-400B is used to collect winding current with electric isolation The adder exists in the output circuit of hall current sensor to ensure safety of control system because the input voltage range of TMS320F28335 A/D module is 0–3.3 V Isolated drive unit The integrated circuit 2SC0108T has some important features such as short-circuit protection, over-current protection, and voltage monitoring for driving insulatedgate bipolar transistor (IGBT) reliably.16,17 Motor speed detection unit The motor speed is acquired by calculating the number of pulses from photoelectric encoder per second Charge–discharge control unit of capacitor This unit is necessary due to the capacitor as energy source for motor actuator The charge command from digital signal processing (DSP) switch IGBT for achieving target that the voltage of capacitor is preset value before operation of disconnector Downloaded from ade.sagepub.com by guest on October 22, 2015 Advances in Mechanical Engineering 240 1.5 Contact stroke 200 1.0 Contact stroke (mm) 180 0.5 0.0 -0.5 1.2 160 1.0 140 0.8 120 100 -1.0 Contact speed 80 0.4 40 0.2 0.0 -20 -50 50 100 150 200 250 300 350 400 -100 100 200 300 400 500 (a) (a) 1.2 240 220 1.5 200 0.5 0.0 -0.5 0.8 160 140 0.6 120 100 80 0.4 Contact speed 60 0.2 40 -1.0 20 -1.5 -20 0.0 50 100 150 200 250 300 350 Contact speed (m/s) Contact stroke (mm) 1.0 Air flux density(T) 1.0 Contact stroke 180 -0.2 Time (ms) Angle(°) -50 0.6 60 20 -1.5 1.4 Contact speed (m/s) Air flux density(T) 1.6 220 -200 -100 100 200 300 400 Time (ms) 400 Angle(°) (b) (b) Figure Air flux density of the motor: (a) no-current mode and (b) max-current mode Figure Dynamic characteristics of disconnector in simulation: (a) closing contact stroke and speed and (b) opening contact stroke and speed AC~220v Power module Rectified unit Isolated drive unit Rotor position detection unit TMS320F2833 Motor speed detection unit Signal processing unit Capacitive chargedischarge unit Contact stroke detection unit RS232 Motor operating mechanism Current detection unit PC control program For remote control of disconnector, reliable control program based on PC is necessary In this article, the PC control program is achieved by VC + + and pass control signal to TMS320F28335 via RS232 bus Instantaneous closing (opening) signal detection unit The positive pole of V battery is connected to the moving contact of disconnector and the negative one connects static contact (see Figure 10) The instantaneous closing (opening) signal appeared when the moving contact touches the static contact PC control program Figure System structure of speed-regulating control system Contact stroke detection unit The linear displacement sensor is adopted to collect signals of contact stroke, and the A/D module is used to transmit those signals to DSP Experiment research To ensure feasibility and availability of the motor and control system, the experimental platform of 550 kV GIS disconnector and motor actuator as shown in Downloaded from ade.sagepub.com by guest on October 22, 2015 Shi et al Static contact Moving contact V Test instrument Battery Resistance Figure 10 Circuit connection of instantaneous closing (opening) signal detection unit Figure 11 is established and then the opening and closing experiment of disconnector is carried out Conventional operation of disconnector In the experiment, the energy-storage capacitance is 108,000 mF, the environment temperature is 25°C, and the voltage of capacitor is 350 V The control command from the control system is emitted to drive motor that pushes contact to achieve operation of disconnector The closing contact stroke and instantaneous closing signal are shown in Figure 12 The three points in Figure 12, namely, A, B, and C, are the open position, the instantaneous closing position, and the closed position of disconnector, respectively The closing operating time of disconnector is 238 ms, and the rotated angle of motor is 82° The switching speed in the initial stage is low relatively because the leaf spring that is installed at the moving contact side produces a contact pressure of 60–100 N approximately, and larger frictional force is formed Therefore, the counter-torque that comes from the above frictional force needs to be overcome by motor actuator which influences the increase in switching speed From Figure 11, the contact bounce ( 1–2°) appeared after the motor rotates at point C due to great impact between moving contact and static contact The three-phase winding currents of motor in closing operation of disconnector are shown in Figure 13 Figure 11 Experimental platform of 550 kV GIS disconnector and motor actuator: (a) experimental platform, (b) angular displacement sensor, and (c) motor Downloaded from ade.sagepub.com by guest on October 22, 2015 Advances in Mechanical Engineering 12 250 Instaneous closing signal 100 50 Contact stroke(mm) B 200 Opening contact stroke 150 100 Instaneous opening signal 50 C A 0 100 200 300 400 500 600 0 100 200 300 Time(ms) 500 600 Figure 14 Opening contact stroke and instantaneous opening signal of disconnector 400 400 300 300 B phase 200 A phase 200 Winding current(A) Winding current(A) 400 Time(ms) Figure 12 Closing contact stroke and instantaneous closing signal of disconnector 100 A phase -100 -200 100 B phase -100 -200 C phase C phase -300 -400 10 Instaneous opening signal(V) 150 Instaneous closing signal(V) Contact stroke(mm) 10 Closing contact stroke B 200 12 A 250 C -300 200 400 600 800 1000 1200 -400 200 Time(ms) 400 600 800 1000 1200 Time(ms) Figure 13 Current of the motor in closing operation Figure 15 Current of the motor in opening operation The commutation of winding currents occurred once during closing operation, and the peak of current is 342 A The opening operating time of disconnector is 265 ms, and the rotated angle of motor is 82° The line AB is over-stroke stage and the line BC is clearance between open contacts (see Figure 14) The mathematical model and simulation of the motor are accurate by comparing simulated with experimental results (see Figures 8, 12, and 14) The three-phase winding currents of the motor in opening operation of disconnector are shown in Figure 15 The commutation of winding currents occurred once during opening operation, and the peak of current is 339 A contact stroke and speed of disconnector with motor actuator in regulating speed operation are shown in Figure 16 The switching speed of disconnector is 0.9 m/s in AB stage After increasing the duty ratio of PWM at point B, this speed increased to 1.2 m/s in BC stage In this experiment, the ratio of PWM has changed from 50% to 90%, and the frequency is 800 Hz The contact bounce appeared near point C due to strong collision between the moving and static contacts This phenomenon can be further controlled by adjusting contact speed in the last stage of closing operation Speed-regulating operation of disconnector In order to achieve intelligent operation of disconnector, the pulse width modulation (PWM) is used for regulating switching speed during closing operation The Conclusion The dynamical coordination characteristics of the motor actuator that is used in disconnector Downloaded from ade.sagepub.com by guest on October 22, 2015 Shi et al 250 2.0 C 1.5 Contact speed 150 1.0 Contact stroke 100 0.5 B 50 Contact speed(m/s) Contact stroke(mm) 200 A 0.0 -50 100 200 300 400 500 600 700 800 Time(ms) Figure 16 Closing contact stroke and speed in speedregulating operation are analyzed The driving motor and speedregulating control system are developed The experimental platform of 550 kV GIS disconnector and motor actuator is established The opening and closing speeds are 1.1 and 1.2 m/s, respectively, when the voltage of capacitor is 350 V The change in switching speed from 0.9 to 1.2 m/s is achieved by motor actuator and speed-regulating control system This novel actuator provides important technical support for suppressing VFTO by adjusting switching speed of disconnector Declaration of conflicting interests The authors declare that there is no conflict of interest 10 11 12 13 Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors 14 References Vinod Kumar V, Thomas JM and Naidu MS Influence of switching conditions on the VFTO magnitudes in a GIS IEEE Trans Power Deliv 2001; 16(4): 539–544 Riechert U, Krusi U and Sologuren D Very fast 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2003, vol 2, pp.491–494 New York: IEEE Paul AR and George M Brushless DC motor control using digital PWM techniques In: International conference on signal processing, communication, computing and networking technologies (ICSCCN), Thuckalay, India, 21–22 July 2011, pp.733–738 New York: IEEE Downloaded from ade.sagepub.com by guest on October 22, 2015 ... largely A novel permanent magnet (PM) motor as actuator of disconnector is presented in this article First, the analysis of dynamical coordination characteristics of motor actuator used in disconnector. .. contact The three-phase winding currents of motor in closing operation of disconnector are shown in Figure 13 Figure 11 Experimental platform of 550 kV GIS disconnector and motor actuator: (a) experimental... out for obtaining the relationship between shaft’s angle of motor and contact stroke of disconnector The operating characteristics of motor during opening and closing operation of the disconnector