advanced motor control technologies – part 1
TRANSCRIPT
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Before We Start
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Meet your Speakers
MODERATOR FEATURED SPEAKER
Dal Y. Ohm
President
Drivetech, Inc.
Aimee Kalnoskas
Moderator
EE World
#EEwebinar
High Volume Applications of Electric Motors
Application Examples
• Appliances & Kitchen Tools
• Residential Fans and Pumps
• Garage Power Tools
• Light Industrial Tools
• Lawn and Garden Tools
• Automotive…….
Power: 10W – 2HP
Power Source: Battery Pack, DC 5-50V, or 100/200VAC 1-Ph
4
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Trends in High Volume Motor Applications
Energy Efficiency
• Induction Motor -> PM Brushless Motor (Rare-Earth)
• Gearless Direct Drive
• Higher Speed Motor
Compact & Low-cost Design
• Box -> Combined Mechanical & Electrical Design
• Drive & Motor in One Package
• Large Scale Integration, Various Microcontrollers
• Effective Heat Removal
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Loss in Motors & Drives
• Efficiency = Pout / Pin
• Copper Loss (I2R)
• Iron Loss (due to magnetic fields)
o Hysteresis & Eddy current Loss
• Mechanical Loss
o Friction, Windage, Fan, Mechanical translators
• Stray Loss (Other misc losses not defined above)
o Mostly due to slot and teeth flux pulsation harmonics
• Drive-related Loss
o Switching & Conduction Loss, Control Power, Fan
o Harmonics and PWM ripple
o Loss due to Non-Optimal Control
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Energy Efficiency
• Power Consumption in Industry - Motors & Drives account for > 2/3
• Overall operational cost ($)
o Installation cost
o Power Bill ( up to 10 times per year)
• Demand charges, Reactive power charges
o Maintenance cost and operating life
• Mandatory Regulation - Efficiency & Power Factor
• How to Improve?
o Consider Premium Efficiency Motor Types (PM)
o Control Methods
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Electromagnetic Torque Production
Cylindrical Machines Reluctance Machines
T = K Ms Mr sin rs T = K Ms2 sin(2rs)
S
N
NS
Ms
rs Ms
S
N
rs
Reaction Torque Reluctance Torque
Mr Mr
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DC and AC Machines
• DC Machines
o Magnetic Poles fixed in space (Stationary Flux)
o Requires Commutator and Brushes
• AC Machines
o Rotor and stator poles are rotating (Rotating Flux)
o PM Synchronous Motors, Reluctance Motors
o Induction Motors s = o + r
• Tendency to minimize electromagnetic energy
• For Consistent Torque Production,
o Consistent Angular relation and mmf magnitude
o Max torque at 90 deg.
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Rotating mmf in 3 phase system
• mmf = (Nse/2)[Ia cos + Ib cos ( -120) + Ic cos ( +120 )
mmf = 1.5 (Nse/2)[Is cos (t - )]
• Constant magnitude, smooth rotation
o sinusoidal current & distributed mmf (winding, slots)
• All poly-phase windings produces sin. distributed mmf!!!
-50 0 50 100 150 200 250 300 350-2
-1.5
-1
-0.5
0
0.5
1
1.5
2Flux Distaribution Waveform
N N
S S
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Desirable Operation of AC Machines
• Objective of Field Oriented Control (FOC)
o Current-generated Flux with rs = 90
o Consistent Flux magnitude
• Sinusoidal Flux Distribution
• When above conditions do not meet significantly?
o Direct IM – Starting, Transient
o Inverters – Transient
o Commutated Drives – Voltage mode, High speed
o Trapezoidal (6-Step) Control
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Drives for Various Motor Types
• Drive Functions
o Vary AC or DC Voltage Electronically to control Speed, or Torque
o Require Commutation for AC motors
• Open-loop
o DC motors (PM or Wound)
o Induction motors (Direct or Inverters)
• Closed-loop with Feedback for Commutation
o Brushless PM motors
o Induction motors with Field Oriented Control (FOC)
• Brushless PM motors - more efficient, compact, high speed!
• Performance of Drives affect efficiency!
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Power Circuit for Motor Drives
• 3 Phase Inverter Topology, Bidiretional
• Minimum # of Switches and Motor Wires
• Optional Regen circuit
DC bus +
DC bus -
AC Motor
R
Q1
Q2
Q3
Q4
Q7
C
Q5
Q6
Rectifier
AC
#EEwebinar 14.
Simple Control of Brushless PM Motors
• Add Commutation!
o 3 phase sinusoidal voltage (or current) based on rotor angle
o 6-step (trapezoidal) control for low-cost drives
o Feedback sensor (or sensorless) required
o Possible phase delay at high speed (T current)
Td
Motor & Load
AC PWMAmplifierPI(D)
*
Positionsensor
Ke
+
-
V* VCommu-
tation
se
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Trapezoidal vs Sinusoidal Control
• T Iacos() + Ibcos(-120) + Iccos(+120)
• Zero ripple condition
cos2() + cos2(-120) + cos2(+120) = 1.5
• All harmonics contributes to loss (ripple & noise)
• Trapezoidal commutation for low-cost, low-power motors
o Wide angle conduction (> 120 )
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Current controlled AC drives
• AC current controller for
o Performs current control & commutation
o Multiple PI controllers
o higher bw (responsive), good performance at high speed
Iabc
Motor & Load
PWMAmplifierPI
*
PositionDetection
Ke
+
-
I*
Vabc
AC CurrentController
se
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Traditional Current Control
• Hysteresis Control (Fsw is controlled by error band)
• Linear Phase Current Control (Fpwm & PI regulator)
• Magnitude control
6-Step, No phase control
Vb*Commutation
Ia*
Vc*Ic*
Va*
Ib*I*
+
+
+
-
-
-
--
PI- V* Commu-
tation
I*
I
Vabc*
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Questions?
MODERATOR FEATURED SPEAKERDal Y. Ohm
President
Drivetech, [email protected]
Aimee Kalnoskas
Moderator
EE World
@DW_Aimee
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This webinar will be available at eeworldonline.com
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