1 / 32

# Brushless Motors - PowerPoint PPT Presentation

Brushless Motors. A servosystem is capable of transforming any mathematical function into a mechanical movement it can replace mechanical elements, such as cams and cam shafts, indexing gears, differentials, etc. A servosystem consists of a servomotor with its control unit.

Related searches for Brushless Motors

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Brushless Motors' - Audrey

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Brushless Motors

• A servosystem is capable of transforming

• any mathematical function

• into a mechanical movement

• it can replace mechanical elements, such as cams

and cam shafts, indexing gears, differentials, etc.

• A servosystem consists of a servomotor with its control unit.

• Servosystems can be used for:

• Positioning; the position, linear or angular, follows a predetermined position function.

• Speed control; the motor speed follows a

• predetermined speed function.

• Torque control; the torque of the motor follows a

• predetermined acceleration function.

• Hybrid control; the system alternates between

• different kinds of control

24 slots

2 rotor poles

Electro-Magnetic AC motor, is aFlux Distribution

21 slots

8 rotor poles

Brushless Solution AC motor, is aPros&Cons:

• Velocity (no sparks at the commutator)

• Efficiency (Torque/Inertia)

• Weight

• Dimensions

• Thermical Dissipation

• Acoustic Noise

• Maintenance

• MTBF

Warm AC motor, is a

Cold

Warm

• Only the stator is warm.

Warm

• Rotor and commutator are warm

Warm

Heiß

Warm

• Both rotor and stator are warm

Thermical Behaviour

1. BL-Servo with MP

2. DC-Servo with MP

3. AC-Servo (ASM squirrel cage)

• Two AC motor, is a brushless motors types exist

• (they differ in stator windings, permanent magnets lay-down, statoric field wave shape):

• AC brushless:

• with sinusoidal field (fcem)

• DC brushless:

• with trapezoidal field (fcem)

Permanent Magnets (PM) types: AC motor, is a

• Ferrite: low cost,

• low Kt, torque loss: 0.2%/K,

• demagnetization temperature: 150C

• Samarium Cobalt (Sm2Co17): high cost,

• high Kt, torque loss: 0.04%/K,

• demagnetization temperature: >150C

• (example: Danaher HD series, Rockwell MPG series)

• Neodimium Iron Boron (NdFeB): medium cost,

• higher Kt, torque loss: 0.09%/K,

• demagnetization temperature: >150C

• (example: Danaher HR series, Rockwell H, Y, 1326, MPL series)

E [kJ/m AC motor, is a3]

400

Nd Fe B

300

Sm Co

200

Steel

Al Ni Co

Ferrite

100

Year

0

1860 1880 1900 1920 1940 1960 1980 2000

Magnetism

• NdFeB (vs. SmCo)

• higher energy content

• worse thermical reversibility

• lower Curie temperature

• lower cost

• corrosion (not present with SmCo)

• bigger resistance in W,

• that in turn limits eddy currents

density AC motor, is a

[g/cm^3]

Curie Temp.

[°C]

Br temp. coeff.[% 1/°C]

Sm2 Co17

8,3

825

-0,03 (20°C ÷ 200°C)

Nd Fe B

7,4

315

-0,1 (20°C ÷ 150°C)

SECo5

Campo coercitivo JHc [kA/m]

500 1000 1500 2000 2500

SECo5

qualitàspeciali

(Field that can demagnetize the magnet)

NdFeB

Sm2Co17

50 100 150 200 250 300 350 400

Max Energetic Product (B*H)max [kJ/m^3]

Temperature that causes

para-magnetic behaviour

(i.e. weak magnetisation)

SmCo vs. NdFeB

Servo System Electrical Scheme on: AC or DC brushless, Kt, Cogging Torque (

PTC on: AC or DC brushless, Kt, Cogging Torque (Resistor

• Positive Thermal Coefficient resistor,used as a sensor

• inside the motor,

• in order to stop the driver/controller

• in case of too-high temperature (before to burn the motor)

Servo Motor Shapes on: AC or DC brushless, Kt, Cogging Torque (

and

Air Cooling

Direct Drive Solution on: AC or DC brushless, Kt, Cogging Torque (

• Problem:

• Motor shaft elastical torsion (i.e. its flexibility):

• resonance frequency

• limited band-width

• low gains in the control loop

• poor kinematic performances

Direct Drive Solution on: AC or DC brushless, Kt, Cogging Torque ((cont’d)

• Possible Solutions:

• Digital Filters (only for constant resonance frequencies)

• High Stiffness Motors (a high inertia would not solve the problem)

• Torque Motors (Motori Coppia) with:

• low velocity

• high stiffness

• they don’t need gearboxes (i.e. they are direct-drive)

Direct Drive Solution on: AC or DC brushless, Kt, Cogging Torque ((cont’d)

• Once solved the resonance frequency problem, the control loop gains can be increased and thus a good accuracy in the position sensor becomes mandatory:

• Resolver:

• 6 arc min = 0.1 degrees

• SinCos Encoder:

• 0.01 arc sec = 2.8E-6 degrees

• or 1nm for linear encoders (righe ottiche)

Position Sensors on: AC or DC brushless, Kt, Cogging Torque (used in theBrushless Motors

Resolver on: AC or DC brushless, Kt, Cogging Torque (

• Characteristics:

• linearity: 0. 1 - 0.5%

• resolution: 0. 1 - 0.5°

• sensitivity: 5 - 10mV/° (Vref =20V)

• frequency: 20KHz

Resolver on: AC or DC brushless, Kt, Cogging Torque ((cont’d)

Resolver on: AC or DC brushless, Kt, Cogging Torque ((cont’d)

• Pro

• absolute in one turn

• low cost

• robust

• Cons

• sinusoidal 20KHz reference voltage

• non-linear output

• brushes in some (old) versions

• It has been the standard position sensor

on brushless motors

Encoder on: AC or DC brushless, Kt, Cogging Torque (

Encoder on: AC or DC brushless, Kt, Cogging Torque ((cont’d)

Encoder on: AC or DC brushless, Kt, Cogging Torque ((cont’d)

Encoder on: AC or DC brushless, Kt, Cogging Torque ((cont’d)

• Encoder types:

• Absolute

• Battery Back Up

• One-Turn Absolute

• Multi-Turn

• Incremental

• SinCos

(resolver output, encoder design,

precise as an encoder)

e.g.: Stegmann mounted

on Rockwell MPL motors

• Degree of Protection on: AC or DC brushless, Kt, Cogging Torque (

• IPXY (e.g.: IP65)

• Digit 1 (X): Solid Objects Protection

• 0 Non Protected

• 1 Protected against solid objects > than 50 mm

• 2 Protected against solid objects > than 12 mm

• 3 Protected against solid objects > than 2.5 mm

• 4 Protected against solid objects > than 1 mm

• 5Dust Protected

• 6Dust Tight

• Digit 2 (Y): Water Protection

• 0 Non Protected

• 1 Protected against dripping water

• 2Protected against dripping water

• when tilted to worse case opening

• 3 Protected against spraying water

• 4 Protected against splashing water

• 5 Protected against waterjets

• 6 Protected against heavy seas

• 7 Protected against the effects of immersion

• 8 Protected against submersion