maxon presentation sizing drive systems with low power dc motors 02-2014

Introductiondrive seminar

Page 1© 2014, maxon motor ag

maxon seminar:

Drive systems with low power DC motors

Typical performance and its significance Selection of drive components Use in dynamic drive systems

© 2014 maxon motor ag, Sachseln, Switzerland

Learning objectives

The participants … get an overview on the parts of a Servo Drive System and

the interaction between them.

learn to read the data sheets of DC motors, EC motors, gearheads.

know the main properties and application ranges of DC and EC motors and be able to select the correct system.

Introductiondrive seminar

Page 2© 2014, maxon motor ag

Agenda Electromate Seminar09.30 – 10.15 Motor selection: What is it all about?

– Application and situation analysis – Extracting key load parameters

10.15 – 10.45 Properties of brushed and brushless DC motors– Design variants– Commutation systems: brushed, brushless

10.45 – 11.00 Coffee break11.00 – 11.30 Motor data sheets

– Characteristic motor lines– Operation ranges

11.30 – 12.15 Motor selection example12.15 – 13.00 Lunch13.00 – 13.30 Motor selection example continued13.30 – 14.30 Introduction to ESCON and EPOS Systems

Media

maxon Formulae Handbook– epaper.maxonmotor.ch/formulaehandbook

maxon catalogue– epaper.maxonmotor.ch/en/

Presentation hand-outs www.maxonmotor.com

– Service & Downloads– Service Desk (FAQ)– maxon academy

http://epaper.maxonmotor.ch/formulaehandbook/

http://epaper.maxonmotor.ch/de/

http://www.maxonmotor.com/

Overview of the selection steps drive seminar

Page 1 Page 1 © 2013, maxon motor ag

Selection of drive components Systematics of the drive selection Situation analysis, boundary conditions

How is the integration into the environment? Preselection

Determining the load requirements Result: key data for load characterization


Systematic selection process

Step 1 overview situation

step 2 step 3 step 4 step 5+6 step 7 load drive gear- motor type sensor head winding controller

ambient condition

communication

power



Step 1: Gain an overview recognize dependencies

operating mode

operating points

power

control concept

boundary conditions

mechanics

motion profile

control accuracy

analyze problem

checklist

Drive system as a black box environment temperature, atmosphere impacts, vibration …

mechanical power force, torque velocity, speed

electrical power current voltage

quality, accuracy resolution mech. play

task set values commands

emissions electro magnetic heat noise …

boundary conditions dimensions service life …



Operating mode

What is a working cycle? How often is it repeated? Which breaks?

continuous operation cyclic operation intermittent Short-time operation

Operating modes continuous (S1)

short term (S2)

working cycles

intermittent (S3)

time

load



Control concept What kind of communication?

– communication with higher level host system

Controlled variable – torque, current – speed, velocity – position

Controlled range, accuracy? – position resolution – speed stability

feedback sensor

– set value range – inputs and outputs

Controller: Heart of the drive system



Control parameter Feedback, sensor Position Speed, Direction

Encoder Hall sensors

Resolver

Speed, Direction DC Tacho IxR

Sensors in feedback systems

Commands, Set values

Motion Controller

Closed loop system for speed or position

Power

∆𝑝𝑜𝑠

∆𝑡

Task and control accuracy The accuracy of control is the combined result

of all components in a drive system! – resolution, precision

command controller motor gearhead, drive load

sensor

control loop

phase shifts time shifts

mechanical play signal amplification



position accuracy – absolute, relative, repeatability – overshoot allowed? – mechanical play in couplings, gearheads, … – encoder resolution and accuracy (linearity)

speed accuracy – Corrected in what time frame? – min. speed nmin by encoder resolution – max. speed nmax by limiting frequency of the encoder – Speed ripple by current and / or torque ripple

electronic components – resolution of A/D-converters, frequency voltage converter – bandwidth, temperature influences

Accuracy of drive systems

t

r

Time and frequency aspects



Power flow

energy is not stored: Power flow – Power: a „constant“ reference value of the drive system

Power consists of 2 components: – voltage and current – velocity and force or speed and torque

– One components can only increase at the expense of the other.

power supply controller motor gearhead,

drive load

sensor

Losses

Pel = U * I Pmech = v * F Pmech = ω * M

Transformation of power

transformation of power – electrical to electrical:

– electrical to mechanical:

– mechanical to mechanical:

efficiency η describes losses

η = 90% η = 90 – 95%

optimum η = 80 - 90%

η = 90% per stage worm gear < 40%

ball screw spindle η = 80 - 90% trapezoidal spindle 40%



Drive design: linear – rotation Drive elements and coupling with load relative position of motor and load

– e.g. bridge a distance with a belt

Mechanical drive concept

Motors up to 500W

stepper motors

asynchronous motors

synchronous motors

DC motors

BLDC motors Stator winding

magnetic rotor

DC behavior (shunt)

n

M I

linear motors f

start

M



Particular boundary conditions dimensions

service life – specific depending on load cycle, ambient conditions and application – given as service hours or numbers of working cycles – limited by the weakest component

temperature, atmosphere

– can influence the achievable power and service life

noise, vibration – specific depending on load cycle, mounting

and ambient conditions, application – influences on service life

Interfaces: Connections

electrical connections – cable type, cable length, colours – plug – strain relief

mechanical interface – mounting type, mounting pilot, threads, number and location of bolt

holes – output shaft: length, diameter, flats – drive elements, pinions, couplings – tolerances



Definition of the load requirements

motion profile and operation points

mass inertia and acceleration

forces and torques

Key values

n(t), M(t) v(t), F(t)

Operating points Pair of

– torque and speed – force and velocity

standard representation: (x,y) = (M,n) or (F,v)

speed n velocity v

torque M force F

acceleration deceleration

dwell



Operating point and motion profile

(M1,n1) acceleration friction and acceleration (M2,n2) const. speed friction only (M3,n3) deceleration friction helps during deceleration (M4,n4) dwell depending on friction

n

M

t

n

1 2 3 1 4

1 2

3 4

extreme operating point

Key load data for characterization

maximum load average effective load (RMS)

maximum velocity or speed vmax / nmax

duration of the maximum load Δtmax

duration of a load cycle Δttot

required position resolution Δs required speed accuracy Δn

Fmax / Mmax F / M

t

FRMS / MRMS

Δtmax

Δttot

...MtMtMtt1M 2

33222

211

totRMS



Example: Conveyor belt for samples

pulley diameter 100 mm maximum mass on belt 3 kg coefficient of friction on

support approx. 0.3 friction force (empty belt) approx. 40 N feed velocity 0.5 m/s supply voltage 24 V

Step 1: Situation Analysis What information is missing? operating mode current task of the drive / setpoints maximum length / diameter service life movement quality emissions environmental conditions control concept


support approx. 0.3 friction force (empty belt) approx. 40N feed velocity 0.5 m/s supply voltage 24 V



Step 2: Load requirements

What information is missing? acceleration value motion profiles Mass (rollers, conveyor belt) Forces / torques …….


support approx. 0.3 friction force (empty belt) approx. 40N feed velocity 0.5 m/s supply voltage 24 V


speed nL =

feed force FL =

torque ML =

power PL =

acceleration Fa =

W25495.0Fv LL

Nm5.24921.0F

2d

L

1

2dL min100

05.05.030v3030

N50409401033.0Fgm R

N5.115.03

tvm L



Example conveyor belt: Key values

Looking for a drive that can accomplish the following: maximum speed nmax 100 rpm

average torque Meff approx. 2.5 Nm maximum torque Mmax approx. 2.7 Nm duration of Mmax 1s

100 rpm

2.5 2.7 Nm

n

M

maxon DC and EC motors drive seminar


Top

3. Low power motors

DC motors EC motors Structure, properties, options

© 2012, maxon motor ag, Sachseln, Switzerland

Top

DC motor designs conventional, slotted

e.g. Dunkermotor

coreless e.g. maxon

DC motors - overview



Top

Conventional DC motor el. connections

housing (magn. return)

winding

commutator

brush system

iron core

permanent magnet (external)

flange


Top

Coreless maxon DC motor (RE 35)

el. connections

self supporting winding

commutator

brushes

permanent magnet (in the centre)

housing (magnetic return)

flange

commutator plate

shaft

ball bearing

ball bearing

press ring

press ring




Top

What makes maxon motors special? no cogging

– no soft magnetic teeth to interact with the permanent magnet – smooth motor running even at low speed – less vibrations and audible noise – any rotor position can easily be controlled – no nonlinearities in the control behavior

compact design – more efficient design of the magnetic circuit – compact magnet, high power density – small rotor mass inertia – high dynamics


Top

What makes maxon motors special? no iron core - no iron losses

– constantly impressed magnetization – high efficiency, up to over 90% – low no-load current, typically < 50 mA

no saturation effects in the iron core – Even at the highest currents the produced torque

is proportional to the motor current. – stronger magnets = stronger motors

low inductance – less brush fire, longer service life – less electromagnetic emissions – easier to suppress interferences: capacitor between connections,

ferrite core at motor cable




Top

maxon DC motor families DCX motor range

– configurable system – high performance motor with NdFeB magnet – high torques and speeds

RE motor range – high performance motor with NdFeB magnet

A-max motor range – attractive price-performance ratio – DC motor with AlNiCo magnet

RE-max motor range – performance between RE and A-max

6 - 65mm

12 - 32mm

13 - 29mm

10 - 35mm

DC motors - variants

Top

DC commutation systems

Precious metal bronze brush body with plated silver contact area silver alloy commutator smallest contact and brush resistance (50 mW) CLL for high service life

Graphite graphite brush with 50%

copper copper reduces the contact

and brush resistance copper commutator graphite serves as lubricant spring system (schematic)

DC motors – commutation



Top

DC commutation: Characteristics Graphite + well suited for high currents and

peak currents + well suited for start-stop and

reversing operation + larger motors (>approx. 10 W)

higher friction, higher no-load

current not suited for small currents higher audible noise higher electromagnetic emissions higher costs

Precious metal + well suited for smallest currents

and voltages + well suited for continuous

operation + smaller motors + very low friction + low audible noise + low electromagnetic interference + cost effective not suited for high current and

peak currents not suited for start-stop operation

DC motors – commutation

Top

EC motors

2/4-pole EC motor internal rotor

Multipole EC flat motor external rotor

electronic commutation – with Hall sensors – sensorless – sinusoidal commutation

Multipole ECi motor internal rotor

EC motors - overview



Top

Brushless DC motor names: EC motor, BLDC motor motor behavior similar to DC motor

– design similar to synchronous motor (3 phase stator winding, rotating magnet)

– the powering of the 3 phases according to rotor position

main advantages: higher life, higher speeds slotless windings: no magnetic detent, less vibrations

becomes more attractive – costs and size of electronics – strength of magnets

EC motors - overview

Top

maxon EC motor families

features in common

EC motors - variants



Top

maxon EC motor families maxon EC motor

– high speeds and torques

EC-max – good value for money – not optimized for performance: relatively high torque – speeds up to 12’000 min-1

EC-4pole – optimized for performance: high torque – speeds up to 25’000 min-1

EC flat motor – very good value for money – speeds up to 12’000 min-1

– relatively large amount of torque EC motors - variants

Top

maxon EC motor

el. connections winding and Hall sensors

housing

PCB with Hall sensors

3 phase knitted maxon winding

magn. return: laminated iron stack

rotor (permanent magnet)

balancing rings

control magnet

preloaded ball bearings

EC motors - variants



Top

EPOS2

block sine

Hall sensors

commutation type

rotor position

feedback

maxon controller families

encoder (+ HS) sensorless

ESCON DECS EPOS2

common goal: applying the current to get the maximum torque perpendicular magnetic field orientation of

- rotor (permanent magnet) - and stator (winding)

knowledge of rotor position with respect to winding

Electronic commutations systems

ESCON

EPOS3 EtherCAT

EC motors – electronic commutation

Top

1 1 0 0 0 1 1 0 1 1 1 0 0 0 0 0 0 1 1 1 0

0° 60° 120° 180° 240° 300° 360° rotation angle

south

north

rotor position from Hall sensor signals

Hall sensor

control magnet

EC-max and EC flat: Power magnet is probed directly

Block commutation




Top

Block commutation +

–

HS3

HS1

HS2

commutation electronics

power stage (MOSFET)

Phase 1

Phase 2

Phase 3

rotor position feedback

com

mut

atio

n lo

gics

EC motor

(magnet, winding, sensor)


Top

DC and EC motor: Comparison DC motor + simple operation and

control, even without electronics

+ no electronic parts in the motor

brush commutation system limits motor life

max. speed limited by commutation system

EC motor + long life, high speeds preloaded ball bearings

+ no brush fire

iron losses in the magnetic return

needs electronics to run more cables more expensive

electronic parts in the motor (Hall Sensor)

Comparison DC and EC



Top

DC and EC motor: Comparison

max. speed power density torque density mech. time (min-1) (W/cm3) (mNm/cm3) const. (ms)

maxon motor family RE (DC) EC EC-max (20 … 100 Watt) EC-4pole EC-flat EC-i

50 000 min-1 10 W/cm3 2 mNm/cm3 10 ms

25 000 min-1 5 W/cm3 1 mNm/cm3 5 ms

Comparison DC and EC

maxon Motor Data and Operating Ranges drive seminar


Top

Motor data and operating ranges of maxon DC motors

Motor behaviour: speed-torque line, current Motor data and operating ranges

© 2012, maxon motor ag, Sachseln, Switzerland

DC motor as an energy converter electrical in mechanical energy

– speed constant – torque constant – speed-torque line

applies to DC and EC motors – "EC" = "brushless DC" (BLDC)

IUPel

2J IRP

MnPmech 30

Overview



Characteristic motor data describe the motor design and general behaviour independent of actual voltage or current

strongly winding dependent values (electromechanical)

almost independent of winding (mechanical)

10 Terminal resistance (phase to phase) R Ω 11 Terminal inductance (phase to phase) L mH 12 Torque constant kM mNm / A 13 Speed constant kn rpm / V

14 Speed / torque gradient Dn/DM rpm / mNm 15 Mechanical time constant tm ms 16 Rotor mass inertia JMot gcm2

Characteristics

Different windings

high resistance winding thin wire, many turns high rated voltage low rated and starting

currents low specific speed (min-1/V) high specific torque (mNm/A)

low resistance winding thick wire, few turns low rated voltage high rated and starting

currents high specific speed (min-1/V) low specific torque (mNm/A)

R

Characteristics



Electromechanical constants

Torque constant kM – produced torque is proportional to motor current – unit: mNm / A

Speed constant kn – law of induction: changing flux in a conductor loop – mostly used for calculating no-load speeds n0

– unit: min-1 / V

Correlation – kM and kn are inverse, but in different units – expressed in the units from catalog:

Ukn n0

indn Ukn

IkM M

Vmin

AmNm000'30kk

1

nM

Characteristics

Motor as an electrical circuit

applied motor voltage U:

+ _

EMF L R

I U EMF: induced voltage Uind

(winding) resistance R winding inductance L • voltage losses over L can be

neglected in DC motors

indtI UIREMFIRLU

IRUUind

Mn kMRU

kn

MMnUkn

MkR000'30Ukn

n

2M

n

D

D

Characteristics



Speed-torque line speed n

torque M

U > UN

U = UN

MH

n0

Dn

DM

current I IA

Ukn n0

MMnUkn n

D

D

Characteristics

Speed-torque gradient

speed n

torque M MH

n0 Dn

DM

strong motor: • flat speed-torque line, small Dn/DM • not sensitive to load changes • e.g. strong magnet, bigger motor

weak motor: • steep speed-torque line, high Dn/DM • sensitive to load changes • e.g. weak magnet, smaller motor

by how much is the speed reduced Dn, if the output motor torque is enhanced by DM?

M1, n1

M2, n2

iH

i2M M

nRk000'30

Mn

D

D

Characteristics



Winding series

speed-torque gradient basically constant for the winding series constant filling factor: a constant amount of copper fills the air gap

n

M

at U constant

thick wire

thin wire

numerous winding variants adjust electrical input power (voltage,

current of power supply) mechanical output power

(speed, torque)

Characteristics

Values at nominal voltage at rated voltage UN

at rated current IN

Motor at stall – resulting stall torque MH

– resulting starting current IA

rated working point – resulting rated speed nN

– resulting rated torque MN

No-load operating point – resulting no-load speed n0

– resulting no-load current I0

describe the special working points:

n

M Values at nominal voltage



Thermal motor data describe the motor heating and thermal limits depend strongly on mounting conditions standard mounting:

heating and cooling – thermal resistance housing-ambient Rth2

– thermal resistance winding-housing Rth1

– thermal time constant of winding tthW

– thermal time constant of motor tthS

temperature limits – ambient temperature range – max. winding temperature Tmax

plastic plate

horizontal mounting

free convection at 25 °C ambient temperature

Specifications

Mechanical motor data

max. permissible speed – limited by bearing life considerations (EC) – limited by relative speed between collector and

brushes (DC)

axial and radial play – suppressed by a preload

axial and radial bearing load – dynamic: in operation – static: at stall

axial press fit force (shaft supported)

describe maximum speed and the properties of bearings

F5 Fd

d l

Specifications



maxon standard tolerances

n

M

1.1 1.0

1.0 0.86 1.16

0.9

Sources – winding resistance ± 7 % – magnetic properties ± 8 % – friction and losses

Results – general tolerance level 5 to 10 % – tolerance in no-load current ± 50 % – tolerance in no-load speed ± 10 %

weaker magnet => enhanced n0 stronger magnet => reduced n0

Values at nominal voltage

Influence of temperature temperature coefficients

Cu + 0.39 % per K AlNiCo - 0.02 % per K Ferrite - 0.2 % per K NdFeB - 0.1 % per K

temperature resistance magnetic properties example: RE motor DT = + 50K R: + 19.5 % kn + 5 % (no-load speed)

kM - 5 % (more current!)

stall torque MH : - 22 %

Values at nominal voltage



Motor limits: operation ranges

- lower ambient temperature - good heat dissipation

- higher ambient temperature - heat accumulation

Speed n

continuous operation

short term operation

MN IN

torque M current I

nmax

Operating Range

Short-term operation overload

load MN 2MN 3MN 4MN

overload duration

5tW

4tW

3tW

2tW

1tW

continous operation

motor may be overloaded for a short time and repeatedly – limit: max. permissible winding temperature – depends on thermal time constant of winding tW and amount

of overload

torque M

thermally prohibitted short term operation permissible


Operating Range

Examples for motor and drive selection drive seminar


Examples for motor and drive selection Continuous operation Cyclic operation maxon selection program


Systematic selection process

Step 1 overview situation

step 2 step 3 step 4 step 5+6 step 7 load drive gear- motor type sensor head winding controller

ambient condition

communication

power



Step 5: Motor selection conveyor belt

selecting the motor type selection of the winding

planetary Gearhead GP 32 A – reduction 51:1

Motor requirements (key values) – Speed 5100 min-1

– average torque 70 mNm

– maximum torque about 75 mNm, 1s

Selection criteria motor type

Commutation (Service life)

Sensor

Shaft Bearing (Service life)

Electrical connection

Ambient condition



Motor type selection Combination with

selected gearhead Nominal torque

(continuous torque) max. torque max. permissible

speed

MN

n

M

continuous operation


deceleration acceleration

nmax NRMS MM

maxon Modular System + motor RE 25, 10W RE 25, 20W A-max 26 RE-max 29

+ motor RE 30, 60W RE 35, 90W A-max 32 EC 32, 80W

according motor type MN suited? maxon modular system

Motor type selection

A-max 26

< 30 mNm RE 25

RE-max 29

RE 30

RE 35

too weak

< 18 mNm

< 30 mNm

too weak

too weak

ca. 80 mNm

100 mNm

good

strong

EC 32

A-max 32

EC 32 flat

< 45 mNm

< 45 mNm

too weak

too weak

< 10 mNm too weak



Step 6: Winding selection Goal: Reach the required speed at maximum possible motor

voltage under maximum load for a given motor size (motor type) this means: sufficiently high

speed constant

motmottheor,0 MMnnn

mot

theor,0theor,nn U

nkk

speed n

torque M

speed-torque line high enough for the required load speed

Mmot

n0,theor

nmot nmot, Mmot

speed-torque line too low for the required load speed


n [rpm]

M

1motmottheor,0 min57007095100M

Mnnn

70 mNm

5100

Vrpm270

215700

Un

kkmot

theor,0theor,nn

select motor 310007: – speed constant kn = 369 min-1/V

needed current – with torque constant kM

A8.215.09.25

70

Ik

MI 0M

maxmax

5700

Feedback and Motion Control maxon drive seminar

Page 1 Page 1 Page 1 © 2013, maxon motor ag

Feedback and Motion Control Feedback systems

– Specifically: Encoder Properties of controllers

– control value – performance, motor type – communication, signal processing


Motion Control System Overview Power Supply

I/O

Encoder Motor

Gearhead

Load

CAN

Supervisor / Master (PLC / PC)

Motion Controller

v(t), F(t)



Sensors in feedback systems

Commands, Set values

Motion Controller

Closed loop system for speed or position

Power

Control parameter Feedback, sensor Position Speed, Direction

Encoder Hall sensors

Resolver

Speed, Direction DC Tacho IxR

∆𝑝𝑜𝑠

∆𝑡

Drive component: Controller



mmc product families controller

family EPOS ESCON

control loops current control

speed control

position control

system architecture

commanded by master system

commanded by digital and analog inputs

setup graphical user interface (Studios)

feedback sensors

needed feedback: • EC: encoder and Hall

sensor • DC: encoder

possible feedback: • encoder

• Hall sensor (EC) • DC tacho (DC)

Configuration – EPOS/ESCON Studio

Configuration

Graphical User Interface

(GUI)

Operation mode Current control Speed control Position control

Motor type DC BLDC Commutation

Feedback type Encoder (resolution) Hall sensor DC Tacho

Communication Bus types Baud rates …

Inputs / Outputs Stop Direction Enable - disable

Ready Speed comparator ….

Selection example – step by stepDrive seminar

Page 1Page 1© 2013, maxon motor ag

Selection ofdrive components

The systematics of the drive selection on a practical application example




Step 1: Situation Analysis

step 2 step 3 step 4 step 5+6 step 7load drive gear- motor type sensor

head winding controller

ambient condition

communication

power

Step 1overviewsituation

What information is missing?

operating mode, motion profile– acceleration– inertias (rollers, belt)

current power supply

control concept, variable– set value– movement quality

maximum length / diameter

service life

environmental conditions– emissions

Given: pulley diameter 100 mm maximum mass on belt 15 kg coefficient of friction on

support approx. 0.2 friction force (empty belt) approx. 30 N feed velocity 0.5 m/s supply voltage 24 V



Step 2: Load Requirements



ambient condition

communication

power


Conveyor belt: load data

Maximum load speed

feed force

acceleration

power

𝑣𝐿 = 0.5𝑚

𝑠

𝐹𝐿 = 𝐹𝑅 + 𝜇 ∙ 𝑚 ∙ 𝑔 = 30 + 0.2 ∙ 15 ∙ 9.8 ≅ 60𝑁

𝑃𝐿 = 𝑣𝐿 ∙ 𝐹𝐿 = 0.5 ∙ 60 = 30𝑊

𝐹𝑎 = 𝑚 ∙∆𝑣𝐿∆𝑡

= 15 ∙0.5

0.5= 15𝑁



Conveyor belt: Key values load

Looking for a drive that can accomplish the following: maximum velocity vmax = 0.5 m/s average force Feff = approx. 60 N maximum force Fmax = approx. 80 N duration of Fmax Δtmax = 0.5 s

0.5 m/s

60 N 80 N

v

F

Step 3: Drive

ambient condition

communication

power






Conveyor belt: load data gear

maximum speed

average torque

maximum torque

𝑛𝐺 =30𝜋∙ 𝜔 = 30

𝜋∙𝑣𝐿𝑑2

= 30𝜋∙0.5

0.05≅ 100𝑟𝑝𝑚

𝑀𝐺,𝑒𝑓𝑓 =𝑑

2∙ 𝐹𝐿 =

0.1

2∙ 60 = 3.0𝑁𝑚

𝑀𝐺,𝑚𝑎𝑥 =𝑑

2∙ 𝐹𝑚𝑎𝑥 =

0.1

2∙ 80 = 4.0𝑁𝑚

Example conveyor belt: Key values

Looking for a drive that can accomplish the following: maximum speed nG,max = 100 rpm average torque MG,eff = approx. 3.0 Nm maximum torque MG,max = approx. 4.0 Nm duration of Mmax Δtmax = 0.5 s

100 rpm

3.0 4.0 Nm

n

M



Step 4: Gearhead selection

ambient condition

communication

power




Step 4: Gearhead selection

Looking for a drive that can accomplish the following: maximum speed nG,max = 100 rpm average torque MG,eff = approx. 3.0 Nm maximum torque MG,max = approx. 4.0 Nm duration of Mmax Δtmax = 0.5 s

?



Limits gear selection

outputspeed n

outputtorque M

MN

continuousoperation

short termoperation

Mmax

Reduction out of input and output speeds:

torque MN > MG,eff

nmax,L

nmax,in

nmax,L

𝑖 <𝑛𝑚𝑎𝑥,𝑖𝑛

𝑛𝑚𝑎𝑥,𝐿

Selection Guide maxon Gear

3 Nm



Conveyor belt: Gearhead selection

planetary gearhead GP 32 C– continuous torque 3 Nm (at least 2 stages)– max. input speed 8000 rpm

– max. reduction

– selected reduction 79:1– efficiency ηG 70 %

requirements motor (key values)– speed

– torque

𝑖 <𝑛𝑚𝑎𝑥,𝑖𝑛

𝑛𝑚𝑎𝑥,𝐿=8000

100= 80: 1

𝑛𝑚𝑜𝑡 = 𝑛𝐺 ∙ 𝑖 = 100 ∙ 79 = 7900 𝑟𝑝𝑚

𝑀𝑚𝑜𝑡 =𝑀𝐺

𝑖 ∙ 𝜂𝐺=

3.0

79 ∙ 70%= 54 𝑚𝑁𝑚

Conveyor belt: Key values motor

Looking for a motor that can accomplish the following: maximum speed nmax = 7900 rpm average torque Meff = 54 mNm maximum torque Mmax = 72 mNm duration of Mmax Δtmax = 0.5 s

7900 rpm

54 72 mNm

n

M



Step 5+6: Selection motortyp & winding

ambient condition

communication

power




Step 5: Motor type selection

MN M

continuousoperation


Nominal torque MN > 54 mNm

max. permissible speed > 7900 rpm

Motor type according to modular systemRE 25RE 30RE 35A-max 26A-max 32RE-max 29EC 32EC-max 22, 25WEC-max 30, 40WEC-4pole 22EC flat 32EC-i 40



Further selection criteria motor type

Commutation (Service life)

Sensor

ShaftBearing(Service life)

Electrical connection

Ambient condition

Conveyor belt motor typeMotor type according to modular system

Nominal torque MN

suitability

RE 25 < 30 mNm Too weak, with brushesRE 30 ca. 90 mNm OK, but with brushesRE 35 ca. 100 mNm strong, but with brushesA-max 26 < 18 mNm too weak, with brushesA-max 32 < 45 mNm too weak, with brushes, nmax= 6000 rpmRE-max 29 < 30 mNm too weak, with brushesEC 32 < 45 mNm too weakEC-max 22, 25W < 23 mNm too weakEC-max 30, 40W < 34 mNm too weak, (60W version => 63 mNm)EC-4pole 22 < 64 mNm OK, only 120W version, builds longEC flat 32 < 23 mNm too weakEC-i 40 < 70 mNm OK



Step 6: Winding selection Goal: Reach the required speed at maximum possible motor voltage

under maximum load for a given motor size (motor type) this means: sufficiently high speed

constantspeed n

torque M

speed-torque line high enough for the required load speed

Mmot

n0,theor

nmot

nmot, Mmot

speed-torque line too low for the required load speed

𝑛0,𝑡ℎ𝑒𝑜𝑟 = 𝑛𝑚𝑜𝑡 +∆𝑛

∆𝑀∙ 𝑀𝑚𝑎𝑥

𝑘𝑛 > 𝑘𝑛,𝑡ℎ𝑒𝑜𝑟 =𝑛0,𝑡ℎ𝑒𝑜𝑟𝑈𝑚𝑜𝑡


n[rpm]

M72 mNm

7900 select motor 311537:– speed constant kn = 497 rpm/V

needed current – with torque constant kM

9100

𝑛0,𝑡ℎ𝑒𝑜𝑟 = 𝑛𝑚𝑜𝑡 +∆𝑛

∆𝑀∙ 𝑀𝑚𝑎𝑥 = 7900 + 17 ∙ 72 ≅ 9100

𝑘𝑛 > 𝑘𝑛,𝑡ℎ𝑒𝑜𝑟 =𝑛0,𝑡ℎ𝑒𝑜𝑟𝑈𝑚𝑜𝑡

=9100

22= 415

𝑚𝑖𝑛−1

𝑉

𝐼𝑚𝑎𝑥 =𝑀𝑚𝑎𝑥

𝑘𝑀+ 𝐼0

=72

19.2+ 0.166 = 3.9 A



Step 7: Sensor and controller

ambient condition

communication

power




maxon presentation sizing drive systems with low power dc motors 02-2014

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