Advanced Motor Control Technologies – Part 1

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Q&A at the end of the presentation

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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

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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

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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

[email protected]

@DW_Aimee

#EEwebinar

This webinar will be available at eeworldonline.com

& email

Tweet with hashtag #EEwebinar

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