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Synchronous reluctance motor
Positioning inside the motor spectrum asynchronous motor reluctance motors permanent magnetized synchronous motor switched reluctance synchronous reluctance transversal flux reluctance old laminations new laminations with flux barrier design
• Stator of the asynchronous motor
(distributed winding)
• Lamination stack with flux barriers
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Synchronous reluctance motor:
Theoretical background
High magnetic conductivity
Low magnetic conductivity
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Saliency : preferred path for the flux

Synchronous reluctance motor
Torque generation
Step 1
Stator flux moves except the air gap only inside the iron
• low magnetic resistance
• lowest “system energy“
Step 2
Stator flux has changed and must make a longer way through the air inside rotor due to the flux barriers in the lamination
• high magnetic resistance
• increased “system energy”
The outcome of this is a torque which acts in direction of the minimum of the system energy
Step 3
• The Rotor moves in the direction of step 1
• With a continuous rotating stator field the rotor is turning continuous, too
• The rotor frequency equals the stator frequency. With a closedloop control, the load angle between stator and rotor is a constant 90 degrees (same as permanent magnet synchronous motor) q d
• Comparable to two magnets sticking together
• Comparable to two magnets flying to each other
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System Efficiency – eco design requirements
Power Drive System
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L , PDS p
L , RPDS
( 100 ; 100 )
( 100 ; 100 )
120%
100%
Reference value
(reference system = reference converter + reference motor)
80%
50%
IES 0
IES 0
20% higher losses than reference value
Reference value
± 20%
20% lower losses than reference value
0%

System features
Energy efficiency rated load and partial load
Efficiency
System with reluctance motor
2
1.
Realization of higher efficiency classes than IE3 is extensive with standard asynchronous motors
System with asynchronous motor
1 kW 5,5 7,5 11,0 15,0 18,5 22,0 30,0
Reluctance* 91,9 92,6 93,5 93,9 94,2 94,5 94,9
IE4* 90,7 91,5 92,3 93,0 93,3 93,7 94,1
IE3*
IE2*
88,0
85,9
89,0
87,0
90,1
88,4
90,9
89,2
91,5
89,9
92,0
90,3
92,6
91,1
*) Minimum efficiency acc. IEC 60034-30-1. Converted to converter operation acc. DIN EN 50598-2 (chapter
5.3.2.6: additional losses depending on harmonics)
2.
Synchronous reluctance motors have a higher efficiency at partial load than standard asynchronous motors
P rated
Power rating 0.5 · P rated
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System features
Power improvement with SF1.2
ASM
Thermal limits
Thermal utilization at rated load
High additional overload capability
• Continuous overload with 20% possible (SF 1.2)
The motor design is developed for highest efficiency, not for maximum thermal utilization.
SRM
Design asynchronous
Engineered for maximum power
• In many applications like building technology the maximum power is required only for some days of the year
• The synchronous reluctance drive is operated during this time in overload with slight reduced efficiency. The rest of the time it operates at highest efficiency.
Design synchronous reluctance
Low temperature radiation via the motor shaft
• Due to low rotor temperature the heat radiation via the motor shaft towards the load is minimal
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High dynamics
Low intrinsic moment of inertia
Rel. intrinsic moment of inertia 1)
180%
160%
140%
120%
100%
80%
60%
40%
20%
0%
Reluctancemotor
Induction motor IE4
Induction motor IE3
Induction motor IE2
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Low intrinsic moment of inertia in comparison with induction motors in
IE2/IE3/IE4
+ Higher dynamics with vector control

Motor technologies for high efficient VFD systems
Performance / Efficiency
Synchronous reluctance motor
+
Frequency converter
+ efficient
+ high dynamic
+ low costs for standard drive systems
Asynchronous motor
IE4
+
Frequency converter + robust
+ low costs for standard drive systems
Permanent magnetized synchronous motor
+
Frequency converter
+ efficient
+ highest dynamic
- intensiv in costs for special applications
+ robust inverter
+ simple control
- intensiv in costs and maintenance for special applications
DC drive
Costs
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Target Applications
Pumps, fans and compressors
• Energy-efficient flow rate control of pumps, fans and compressors in the process and water industries
Conveyor technology
• Energy efficient and dynamic conveyor technology operation for bulk products and packaged goods
Machinery construction
• New opportunities for machine builders as a result of simple speed control and synchronous speed operation
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Highlights
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Thank You for your Attention
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