Simplified Analysis Technique for Double Layer
Non-overlap Multiphase Slip Permanent Magnet
Couplings in Wind Energy Applications
Petrus JJ van Wyk
-
Prof. Maarten J. Kamper
Renewable Energy Postgraduate Symposium
July 13, 2015
Petrus JJ van Wyk
EMLAB - Stellenbosch University
1/22
Presentation Outline
1
Introduction
2
“Slip Coupler” Concept
3
Proposed Analysis Technique
4
Modelling
5
Results
6
Conclusion
Petrus JJ van Wyk
EMLAB - Stellenbosch University
2/22
Introduction
Electromagnetic couplings are well known in industry
Permanent magnet couplings
Eddy current couplings
Recently a new concept wind generator was introduced
1
Slip PM coupling
Sharing common PM rotor with a Synchronous Generator
Called Slip Synchronous PMG
Slip-PMC filters transient torque
Double layer, non-overlap winding slip-PMC introduced in
Potgieter (2014)2
Calculations made for these machines - accurate, but not
necessarily applicable to all machines
1
J.H.J. Potgieter and M.J. Kamper (2012), Design of New Concept Direct Grid-Connected
Slip-Synchronous Permanent-Magnet Wind Generator, IEEE Transactions on Industry Applications 48(3),
913 – 922.
2
J.H.J. Potgieter and M.J. Kamper (2014), Optimum Design and Comparison of Slip
Permanent-Magnet Couplings With Wind Energy as Case Study Application, IEEE Transactions on
Industry Applications 50(5), 3223 – 3234.
Petrus JJ van Wyk
EMLAB - Stellenbosch University
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Introduction
SS-PMG
PMSG
Grid
Gearbox
Slip
PMC
PMSG
Grid
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EMLAB - Stellenbosch University
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“Slip Coupler” Concept
The machine analysed in this paper is a
Double layer,
Short Circuited,
Non-overlap winding,
Permanent magnet motor
Operating under slip conditions as a coupling.
This machine is thus referred to as a slip coupler.
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EMLAB - Stellenbosch University
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“Slip Coupler” Concept
Slip coupler specifications:
28 poles
30 slots
Solid aluminium windings
Output speed of 600 r/min
Rated slip of 3%
Torque at rated slip - 35 Nm
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EMLAB - Stellenbosch University
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Proposed Analysis Technique
The slip coupler concept presents several unique analysis problems:
It is a 30 phase machine
Different cross sectional areas between upper and lower layer coils
Different resistance values
Thus different current values
Cannot be analysed using standard three-phase analysis methods
How can such a machine be analysed?
Petrus JJ van Wyk
EMLAB - Stellenbosch University
7/22
Flux Linkage (mWb·turn)
Proposed Analysis Technique
0.5
0
−0.5
0
Petrus JJ van Wyk
90
180
270
Rotor Angle (degrees, electrical)
EMLAB - Stellenbosch University
360
8/22
Proposed Analysis Technique
Phases are divided into sets of three:
Each phase is chosen 120 electrical degrees apart
28 pole machine, also 120 mechanical degrees apart
30 phase machine means 10 sets
Phases in set must be from same winding layer
A1
a01
B1
b01
a1
+
+
+
+
.....
a02
a2
C1
c01
b1
Slot 1
Slot 2
Petrus JJ van Wyk
+
+
.....
b02
b2
A2
c1
Slot 3
Slot 10
Slot 11
Slot 12
c02
c2
B2
C2
Slot 13
Slot 20
Slot 21
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Slot 22
Slot 23
9/22
Flux Linkage (mWb·turn)
Proposed Analysis Technique
0.5
0
−0.5
0
Petrus JJ van Wyk
90
180
270
Rotor Angle (degrees, electrical)
EMLAB - Stellenbosch University
360
10/22
Flux Linkage (mWb·turn)
Proposed Analysis Technique
0.5
0
−0.5
0
Petrus JJ van Wyk
90
180
270
Rotor Angle (degrees, electrical)
EMLAB - Stellenbosch University
360
11/22
Proposed Analysis Technique
Each set contains balanced three-phase quantities
Sets can be analysed separately (“10 separate machines”)
Calculated torques are added to get total torque
Flux Linkage (mWb)
Allows use of all existing three-phase theory
0.5
0
−0.5
0
Petrus JJ van Wyk
90
180
270
360
Rotor Angle (degrees, electrical)
EMLAB - Stellenbosch University
12/22
Modelling
Ri
Iqi
Ri
ωsle λqi −
+
Iqi
ωsle λdi
−
+
Idi
q
φ
Idi
√
2IRMSi
d
dq Voltage equations are written as:
0 = Ri Idi − ωsle λqi
(1)
0 = Ri Iqi + ωsle λdi
(2)
with i as the set number.
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EMLAB - Stellenbosch University
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Results
After machine optimisation is done, method is assessed:
Method uses four time-stepped static FE solutions
Machine is also simulated using a transient FE solution
Transient is considered as most accurate method available
Results between static and transient are compared
Unfortunately, prototype still under construction, thus no
experimental results
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EMLAB - Stellenbosch University
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Per Phase Flux Linkage (mWb)
Results - Flux Linkage
0.5
0
−0.5
0
90
180
270
Rotor Angle (degrees, electrical)
λupper coil static
λupper coil transient
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360
λlower coil static
λlower coil transient
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Results - Current
Per Phase Current (A)
400
200
0
−200
−400
0
90
180
270
Rotor Angle (degrees, electrical)
Iupper coil static
Iupper coil transient
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360
Ilower coil static
Ilower coil transient
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Results - Torque
Torque (Nm)
36.5
36
35.5
35
0
90
180
270
Rotor Angle (degrees, electrical)
Tstatic
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360
Ttransient
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Results - Slip vs Torque
Torque (Nm)
150
100
50
0
0
5
10
15
20
25
Slip (%)
Tstatic
Petrus JJ van Wyk
Ttransient
EMLAB - Stellenbosch University
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Conclusion
It is concluded that
Static and transient
Currents and flux linkagesTorque, over a large slip range-
are in excellent agreement
Proposed method of grouping phases into sets gives accurate
results
Fast results - only four static FE simulations
Can be used for optimisation of similiar machines
Much faster than transient solutions
Method can be used on any double layer, non-overlap, multiphase
PM machine
Petrus JJ van Wyk
EMLAB - Stellenbosch University
19/22
Recent Progress on Prototype
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Recent Progress on Prototype
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EMLAB - Stellenbosch University
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Thank You
Petrus JJ van Wyk
EMLAB - Stellenbosch University
22/22