Advances in Mechanical Engineering 1–9 Ó The Authors 2015 DOI: 10.1177/1687814015575428 aime.sagepub.com Design of permanent magnet motor actuator used in 550 kV gas-insulated switchgear
Trang 1Advances in Mechanical Engineering 1–9
Ó The Author(s) 2015 DOI: 10.1177/1687814015575428 aime.sagepub.com
Design of permanent magnet motor
actuator used in 550 kV gas-insulated
switchgear disconnector
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 require-ments 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: 7 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
elec-tronic devices connected to GIS enclosure.1–4 One of
the important influential factors of VFTO is the
switch-ing speed of the disconnector The research on
suppres-sing 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
Trang 2actuator of GIS disconnector mainly included spring
mechanism, hydraulic mechanism, and electromagnetic
mechanism A new type actuator of disconnector is
pre-sented, 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
sim-plifies 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
opera-tion of disconnector, the investigaopera-tion on the possibility
of varying speed operation was performed, and the
actuator that can switch with different speeds is
devel-oped, 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
devel-opment 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
operat-ing characteristics of motor duroperat-ing openoperat-ing and closoperat-ing
operation of the disconnector are simulated The
mag-netic saturation of motor tooth is taken into
consider-ation in the simulconsider-ation 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
The whole structure of 550 kV GIS disconnector and
its mechanical connection with motor actuator are
shown in Figure 1 This system diagram mainly
included three parts, namely, disconnector, driving
motor, and control system
Analysis of dynamical coordination characteristics of
motor actuator used in disconnector
The structure of disconnector transmission mechanism
is shown in Figure 2 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)
uBAD= ua 408
AD = AB cos uð BADÞ
BD = AB sin uð BADÞ
BE = AF AD
CE = ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
BC2 BE2 p
CF = CE + BD
CC0= CF C0F
8
>
>
>
>
>
>
ð1Þ
where uais 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 3 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 corre-sponding 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 struc-ture, 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
1 The electromagnetic field of the motor is regarded as quasi-static field
2 The end effect of the motor is included by end leakage inductance from circuit equation
3 The influence of eddy-current effect is neglected The electromagnetic field equations of the motor are
1
m1∂A
∂n G 2
m2∂A
∂n
G2+
= JS
AjG 1= 0
∂
∂x 1
m1∂A
∂x
+ ∂
∂y 1
m1∂A
∂y
= aaJZa abJZb acJZc
8
>
<
>
:
ð2Þ
where JS is the current density of PM surface; aa, ab, and ac are the current facts of three-phase windings, respectively; G1is the stator outer boundary; G2is the boundary of PM; JZa, JZb, and JZcare the current den-sities in the z-axis direction of three-phase windings, respectively; and m1and m2are the relative permeabil-ities of motor air gap and PM, respectively
The circuit equation of the motor windings is
U
½ = E½ + R½ I½ + L½ d I½
where [U] is the voltage vector, [E] is the electromotive force voltage vector, [R] is the resistor matrix of
Trang 3windings, [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
aSb
akik, k = a, b, c ð4Þ
where N0is the number of single windings; a is the
num-ber of parallel branches; Sbis the sectional area of single
winding; and ia, ib, and icare the currents of three-phase
windings, respectively
The induced electromotive force of windings is
ei= d
dt
2pLefN0
aSb
Xq 1
Xn m
m = 1
Dm Am
i + Am
j + Am k
3
0
@
1 A ð5Þ
where p is the number of pole-pairs, Lefis the effective length of armature, nmis the total number of elements
in the computational domain, q is the number of slots per pole per phase, Dmis 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
JdO
where J is the equivalent moment of inertia in motor spindle side, O is the angular velocity of motor rotor,
Temis the electromagnetic torque of motor, TL is the load torque, and ROis the drag coefficient
The equation of electromagnetic torque is
Tem=iaea+ ibeb+ icec
Static contact
Moving contact
Connecting shaft
Connecting lever
Pull bars
Swing lever
Driving Motor Motor shaft
Limit hoding device Control system
Photoelectric encoder
V
V
Figure 1 System diagram of 550 kV GIS disconnector and motor actuator.
Moving contact
A
B 0
C 0
B 1
C 1 B
C
80°
Rotated spindle
Connecting lever
Insulating tension pole D
E F
Figure 2 Structure of disconnector transmission.
Trang 4The rotated angle can be expressed as
dua
The electromagnetic torque is calculated by the
Maxwell stress method
Tem=Lef
m0
ð 2p
0
r2BrnBundua ð9Þ
where r is the radius of air gap; Brn and Bun are the
radial and tangential components of air gap flux
den-sity, respectively; and m0is the permeability of vacuum
The discrete equations that describe dynamic
char-acteristics of the motor can be obtained using weighted
integral method and coupling equation (3) The
dynamic characteristics of the motor are calculated by
solving above equations by Newton–Raphson and combining equation (6).14,15
The structure and major parameters of the motor are shown in Figure 4 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 5
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 den-sity of the motor as shown in Figures 6 and 7, respec-tively, 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
-10 0 10 20 30 40 50 60 70 80 90
Opening operation
Contact stroke(mm)
A
B
C
Closing operation
Figure 3 Relationship between rotated angle of motor and contact stroke.
Table 1 Motor parameter.
Stator Rotor
Motor shaft Photoelectric
encoder
A phase
B phase
C phase
Figure 4 Structure of the motor.
Trang 5magnetic 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
nonsa-turated status according to B-H curve of stator
mate-rial (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
max-current mode due to torque ripple and armature
reac-tion The average air flux densities of the motor in
these modes are more than 1 T that meet the design
requirements of the motor
The dynamic characteristics of the motor used in
dis-connector are obtained by numerical simulation as shown
in Figure 8 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
posi-tion, and the closing speed is the average speed in
three-fourths 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
require-ment of 550 kV GIS disconnector
Design of control system
According to the mechanical requirements of
discon-nector and operating characteristics of the motor, the
speed-regulating control system based on
TMS320F28335 is developed, and its system structure
is shown in Figure 9
The main parts of this control system are introduced
as follows:
1 Current detection unit The hall current sensor
CHF-400B is used to collect winding current
with electric isolation The adder exists in the out-put 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
2 Isolated drive unit The integrated circuit 2SC0108T has some important features such as short-circuit protection, over-current protection, and voltage monitoring for driving insulated-gate bipolar transistor (IGBT) reliably.16,17
3 Motor speed detection unit The motor speed is acquired by calculating the number of pulses from photoelectric encoder per second
4 Charge–discharge control unit of capacitor This unit is necessary due to the capacitor as energy source for motor actuator The charge com-mand from digital signal processing (DSP) switch IGBT for achieving target that the vol-tage of capacitor is preset value before opera-tion of disconnector
Permanent magnet
Limiting armature Motor shaft
Figure 5 The structure of permanent magnet limiting and
keeping device.
Figure 6 Magnetic field distribution of the motor: (a) no-load mode and (b) max-current mode.
Trang 65 Contact stroke detection unit The linear
displa-cement sensor is adopted to collect signals of
contact stroke, and the A/D module is used to
transmit those signals to DSP
6 PC control program For remote control of dis-connector, reliable control program based on
PC is necessary In this article, the PC control program is achieved by VC + + and pass con-trol signal to TMS320F28335 via RS232 bus
7 Instantaneous closing (opening) signal detection unit The positive pole of 9 V battery is con-nected 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
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
-50 0 50 100 150 200 250 300 350 400
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Angle(°)
(a)
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Angle(°)
(b)
Figure 7 Air flux density of the motor: (a) no-current mode
and (b) max-current mode.
-20 0 20 40 60 80 100 120 140 160 180 200 220 240
Time (ms)
Contact stroke
Contact speed
-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
(a)
-20 0 20 40 60 80 100 120 140 160 180 200 220 240
Time (ms)
Contact stroke
Contact speed
0.0 0.2 0.4 0.6 0.8 1.0 1.2
(b)
Figure 8 Dynamic characteristics of disconnector in simulation: (a) closing contact stroke and speed and (b) opening contact stroke and speed.
Current detection
unit
Capacitive
charge-discharge unit
Motor speed
detection unit
Rotor position
detection unit
Contact stroke
detection unit
PC control program RS232
AC~220v Power module
Figure 9 System structure of speed-regulating control system.
Trang 7Figure 11 is established and then the opening and
clos-ing 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 posi-tion, and the closed position of disconnector, respec-tively 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 ( 6 1–2°) appeared after the motor rotates at point C due to great impact between moving contact and static con-tact The three-phase winding currents of motor in clos-ing operation of disconnector are shown in Figure 13
Static contact
Moving contact
V
Test instrument
Figure 10 Circuit connection of instantaneous closing
(opening) signal detection unit.
Figure 11 Experimental platform of 550 kV GIS disconnector and motor actuator: (a) experimental platform, (b) angular
displacement sensor, and (c) motor.
Trang 8The 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
mathemati-cal model and simulation of the motor are accurate by
comparing simulated with experimental results (see
Figures 8, 12, and 14) The three-phase winding
cur-rents 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
Speed-regulating operation of disconnector
In order to achieve intelligent operation of
disconnec-tor, the pulse width modulation (PWM) is used for
reg-ulating switching speed during closing operation The
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 phenom-enon can be further controlled by adjusting contact speed in the last stage of closing operation
Conclusion
1 The dynamical coordination characteristics of the motor actuator that is used in disconnector
0
50
100
150
200
250
Time(ms)
Closing contact stroke
Instaneous closing signal
A
B C
0 2 4 6 8 10 12
600 500 400 300 200 100
0
Figure 12 Closing contact stroke and instantaneous closing
signal of disconnector.
-400
-300
-200
-100
0
100
200
300
400
Time(ms)
B phase
C phase
A phase
Figure 13 Current of the motor in closing operation.
0 2 4 6 8 10 12
0 50 100 150 200
250
B
Instaneous opening signal
Opening contact stroke
Time(ms)
A
C
600 500 400 300 200 100 0
Figure 14 Opening contact stroke and instantaneous opening signal of disconnector.
-400 -300 -200 -100 0 100 200 300 400
Time(ms)
A phase
B phase
C phase
Figure 15 Current of the motor in opening operation.
Trang 9are analyzed The driving motor and
speed-regulating control system are developed The
experimental platform of 550 kV GIS
discon-nector 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
2 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.
Funding
This research received no specific grant from any funding
agency in the public, commercial, or not-for-profit sectors.
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800 0.0 0.5 1.0 1.5 2.0
-50
0
50
100
150
200
250
Contact speed
C
A
Time(ms)
B Contact stroke
Figure 16 Closing contact stroke and speed in
speed-regulating operation.