Unit-I Synchronous Reluctance Motor (SyncREL)
Post on 20-Apr-2022
10 Views
Preview:
Transcript
Unit-I Synchronous Reluctance Motor
(SyncREL)
by
Sakthisudhursun B.
Assistant Professor
Department of Electrical and Electronics Engineering,
Mepco Schlenk Engineering College,
Sivakasi www.vidyarthiplus.com
www.Vidyarthiplus.com
Why in recent days reluctance machines are popular?
• Simple and Robust construction
• No copper loss
• No requirement of permanent magnet
• Less initial cost
• Stator can be easily cooled
Commercial introduction: ABB
Power rating available: 17kW to 350kW
Introduction
www.vidyarthiplus.com
www.Vidyarthiplus.com
Advantages over Permanent Magnet Machines:
• No permanent magnet is used hence reduces the over all initial
cost
• It can operate at extremely high temperature & speed
Limitation over Permanent Magnet Machines:
• High KVA rating of the converter
• Power factor and efficiency is not as high as Permanent magnet
machines
Introduction
www.vidyarthiplus.com
www.Vidyarthiplus.com
Reluctance Machine
Switched Reluctance
Machine (SRM)
Synchronous Reluctance
Machine (Syncrel)
Types of Reluctance Machine
www.vidyarthiplus.com
www.Vidyarthiplus.com
SRM Syncrel
Double Salient structure (i.e.) Both stator and Rotor has Salient structure
Only Rotor has Salient structure
New stator structure hence initial cost is more to make
Standard 3-phase induction machine stator can be used
Concentrated Winding Sine distributed winding
Special converter required to drive SRM
Conventional inverter is required to drive Syncrel
Difficult to modeling due to non linearity in both stator and rotor
Normal AC machine modeling can be applied
Torque pulsation is more Relatively smoothed torque is produced
Relatively difficult to control due to non linearity
Easy to control
Comparison between SRM & SYNCREL
www.vidyarthiplus.com
www.Vidyarthiplus.com
Torque generation in Salient Pole Synchronous machine:
1) Electromagnetic torque
2) Reluctance torque
Electromagnetic Torque:
Due to the interaction between magnetic field produced by rotor & armature current
Reluctance Torque:
Due to the difference between the direct axis and quadrature axis reactance
What is a synchronous reluctance (SYNCREL) motor?
SYNCREL is a synchronous motor in which the torque is produced only due
to the difference between the direct axis and quadrature axis reactance
Synchronous Reluctance Motor (SyncREL)
2sin
X2X
XXVsin
X
VE3T
qd
qd2
d
www.vidyarthiplus.com
www.Vidyarthiplus.com
www.vidyarthiplus.com
www.Vidyarthiplus.com
Construction
Stator & Rotor
www.vidyarthiplus.com
www.Vidyarthiplus.com
Stator:
• Armature or stator core is made of ferromagnetic material and laminated
Why?
• To reduce the hysteresis and eddy current losses
• Stator core is attached to the stator frame
• Slots for housing the armature winding are provided along the inner
periphery of stator core
• Semi-closed slots are used
• Stator carries three-phase winding and arranged for required number of
poles
• Distributed windings are used
Construction
www.vidyarthiplus.com
www.Vidyarthiplus.com
Rotor:
• Rotor is constructed in such a way that the armature inductance varies
sinusoidally
• Inductance should be maximum along direct axis & minimum along
quadrature axis
• Difference between direct axis & quadrature axis inductance should be as
large as possible
Why?
• To generate the maximum torque
Different type of Rotor Construction:
• Segmental rotor
• Radially laminated rotor
• Axially laminated rotor
Construction
www.vidyarthiplus.com
www.Vidyarthiplus.com
Obtained by scooping out iron material in the quadrature axis
Construction
www.vidyarthiplus.com
www.Vidyarthiplus.com
www.vidyarthiplus.com
www.Vidyarthiplus.com
Axially Laminated Rotor:
• Flux barriers are introduced in the quadrature flux path
• Flux barriers are made of thin sheets of non-magnetic material
• Brass or aluminimum is used as flux barriers
• Direct axis inductance is not affected much by flux barriers as their
thickness is very small
Radially Laminated Rotor:
• Compared to axially laminated rotor they are cheaper & easier
• Since circular laminations can be used
• Motor has self starting capability
Construction
www.vidyarthiplus.com
www.Vidyarthiplus.com
Other Types of Radially Laminated Rotor:
www.vidyarthiplus.com
www.Vidyarthiplus.com
Working Principle
• Balanced 3-phase sinusoidal supply voltage is given in the stator
• Produces a rotating magnetic field in the air gap which rotates at
synchronous speed
• Rotor accelerates towards synchronous speed with the help of
damper winding or cage winding provided
• Rotating magnetic field exerts reluctance torque on the rotor to align its
projecting poles or d-axis to have a minimum reluctance torque
• SyncREL starts as an induction motor and at running condition reluctance
torque pulls the rotor in synchronism with stator field
www.vidyarthiplus.com
www.Vidyarthiplus.com
• Rotor accelerates towards synchronous speed
• At a “critical” speed, the low-reluctance paths provided by the salient poles will cause them to “snap” into synchronism with the rotating flux.
Working Principle
www.vidyarthiplus.com
www.Vidyarthiplus.com
Working Principle
www.vidyarthiplus.com
www.Vidyarthiplus.com
Operation (continued)
• When the rotor synchronizes, slip is equal to zero
• Rotor pulled around by “reluctance torque”
• Figure at right shows the rotor synchronized at no load
www.vidyarthiplus.com
www.Vidyarthiplus.com
Operation (continued)
• A “step” increase in load slows the rotor down, and the rotor poles “lag” the stator poles.
• The angle of lag, δ, is called the “torque angle”.
• The maximum torque angle, δmax = 45°.
www.vidyarthiplus.com
www.Vidyarthiplus.com
Operation at maximum load
• Maximum load is when δ = 45°.
• If load increases so that δ>45°, the flux path is “over stretched” and the rotor falls out of synchronism.
• Motor runs at slip speed
www.vidyarthiplus.com
www.Vidyarthiplus.com
Applications
• Pumps
• Conveyors
• Synthetic fiber manufacturing industries
• Textile industries
• For positioning control rods in nuclear reactors
www.vidyarthiplus.com
www.Vidyarthiplus.com
Permanent magnet assisted SynRM (or)
Hybrid Synchronous reluctance motor
• When PMs are inserted into the rotor flux
barriers of a synchronous reluctance
motor, it becomes a permanent magnet
assisted synchronous reluctance motor
• The amount of PM flux is quite lower than the amount of rated flux
Features:
• Has Combined reluctance and magnetic alignment torque
• High inductance
• High field weakening capability
• Under excited operation for most of the load condition www.vidyarthiplus.com
www.Vidyarthiplus.com
Hybrid Synchronous reluctance motor
Radially magnetized Circumferentially magnetized
www.vidyarthiplus.com
www.Vidyarthiplus.com
Radially magnetized:
• Magnet area is smaller than pole area at the rotor surface
• Has considerable reluctance torque & field weakening capability
Reason:
Permeance to q-axis flux is high
Axially magnetized:
• Magnet area is exceeds the pole area at the rotor surface
• Has less reluctance torque & limited field weakening capability
Reason:
Permeance to q-axis flux is very low
www.vidyarthiplus.com
www.Vidyarthiplus.com
Controller for SyncREL
www.vidyarthiplus.com
www.Vidyarthiplus.com
www.vidyarthiplus.com
www.Vidyarthiplus.com
top related