Electronic starters and variable speed drives ATV71 the motor control

Voltage Vector Control CTT=SVC U  Performance : optimization of the settings current limit adjustable from 150% to 165% In of the drive... Voltage vector control CTT=SVC U  Torque cur

Training module 3

The motor control

Dominique GENDRON

François MALRAIT

Introduction

The ATV71 includes several motor control laws.

These different laws allow the drive to be adapted to a great

variety of induction motors and machines.

This module describes these command law, their application,

as well as their associated functions.

Summary

The motor control

II.Motor control menu

III Protection against motor

overvoltage

IV Specific applications

Flux vector control basics

The motor control laws

Flux vector control basics

electrical parameters (current, voltage, flux) are alternating.

equations in such a fashion so as to::

Flux  r = K1 Id Torque C = K2  s Iq

Flux vector control basics

the flux producing current

entire speed range.

correction of torque and flux.

• Thus the performance is much better, for low speed torque, dynamic response,

and speed precision compared to a scalar volts/Hertz law.

Flux vector control basics

 Comparison of U/F and Vector control

Automatic Compensation

(Rs and slip)

Manual Compensation (U0 voltage at origin) C/Cn

Flux vector control basics

 Torque/current relationship

motor as well as the optimization of the command law.

In 1.5 In

ATV71The motor control laws

Voltage vector control law SVC U

Voltage vector control (CTT=SVC U)

• Voltage vector control is a compromise between performance and robustness.

 Applications :

Voltage Vector Control (CTT=SVC U)

 Performance :

optimization of the settings (current limit adjustable from 150% to 165% In of

the drive)

Voltage vector control (CTT=SVC U)

precision and insures sway detection.

and up to one size below.

Voltage vector control (CTT=SVC U)

+ -

(d,q)  (a,b,c)

Speed Estimate

Voltage Calculation Current Regulation

Current measurement (d,q)  (a,b,c)

Motor

Speed

Ramp

Speed Regulation

Current/torque Limitation

+ +

 cons

Id

Vc Va Vb

Voltage vector control (CTT=SVC U)

 Torque curves (11kW 400V motor quadrant)

Voltage vector control (CTT=SVC U)

 Torque curves (11kW 400V motor quadrant 0-5Hz)

ATV71The motor control laws

Current vector control law SVC I and FVC

Current vector control

• The current vector control law allows the drive to attain better static and dynamic performance

for torque and speed.

Current vector control

 Performance :

optimization of the settings (current limit adjustable from 150% to 165% In

drive)

braking resistor.

Current vector control (CTT=SVC I)

 Performance in open loop

Current vector control (CTT=SVC I)

 Open loop

+ -

(d,q)  (a,b,c)

Speed Estimation

Voltage calculation Current regulation

current measruement (d,q)  (a,b,c)

Motor

Speed

Ramp Regulation Speed

Current/torque Limit

+ +

Estimate of magnetizing inductance

 cons

Id

Vc Va Vb

Current vector control (CTT=SVC I)

 Torque curves in open loop (motor quadrant 11kW)

Current vector control (CTT=SVC I)

 Torque curves in open loop (motor quadrant 11kW 0-5Hz)

Current vector control (CTT=FVC)

 Performance in closed loop

• Torque at 0 speed is available in motoring or generating quadrant

• Speed precision is 0,02%* of the nominal speed

• Cannot be used with motors in parallel.

• Torque regulation mode :

– Precision 5%

– Up to +/-300% of nominal torque (Cn)

* Indicative values dependent upon the resolution of the encoder

Current vector control (CTT=FVC)

 Closed loop

+ -

(d,q)  (a,b,c)

Speed Measure

Voltage Calculation Current Regulation

current measurments (d,q)  (a,b,c)

Motor

Speed

Ramp

Speed Regulation

+ +

Estimate of magnetizing inductance

 cons

Id

Vc

Va Vb

Encoder

Current vector control (CTT=FVC)

 Closed loop torque curves

 Torque curves in closed loop (motor quadrant 11kW)

Current vector control (CTT=FVC)

 Torque curves in closed loop (motor quadrant 11kW 0-5Hz)

Current vector control

Speed ramps

ACC/DEC

Speed feedback

+

-Apply torque

Speed loop

Torque/current limitation TSS=LIx

Torque rampe

Torque controller

TR1=Aix,

DBN/DBP Dead band

Current vector control

 Prefluxing

• To obtain maximum torque upon application of the run command the magnetic flux must be established in the motor beforehand.

• To do this the flux can be either maintained or established while the motor is stopped by using a logic input.

Vector Control

 2 point vector control

• The parameters UCP and FCP allow the limitation of output voltage above the nominal frequency FRS if the distribution voltage is higher than that of the motor.

Nominal motor voltage UNS

Output voltage

UCP

FCP FRS

Frequency

Distribution Voltage

Volts / Hertz law (U/f) The motor control laws

Volts/Hertz (U/f)

• Without speed estimation, or compensation (slip and RI)

• 2 profiles possible: U/f 2 points and U/F 5 points

– motors powered through a transformer – tests on little motors

Volts / Hertz 2 points (CTT=UF2)

• UNS and FRS define the operating points of the motor.

• U0 is the voltage applied to the motor at 0 hz (boost)

U stator

Output Frequency

U0

UNS

FRS

Volts / Hertz 5 points (CTT=UF5)

• 5 points U1:F1 to U5:F5 allows adaptation of the V/F profile to the torque profile of the load

• For example, permits avoiding resonance phenomena with high speed motors.

FRS F5

Volts / Hertz (U/f )

(d,q)  (a,b,c)

Voltage Calculation Current Regulation

current measurement (d,q)  (a,b,c)

Motor

Speed

Ramp

Current Limitation

U0

 ref

Id Iq

Volts / Hertz (U/f )

 Torque curves U/F2 (motor quadrant 11kW 400V)

Synchronous motor law The motor control laws

Synchronous Motor

• The synchronous motor law permits the control of permanent magnet

synchronous motors with either smooth poles or not

 Applications :

motors are used to reduce the size

Synchronous Motor

acceleration and deceleration.

optimization of the settings (current limit adjustable from 150% to 165% In drive)

of synchronous motors (3 to 6 Cn).

vector control (pseudo-defluxed).

Synchronous Motor

+ -

(d,q)  (a,b,c)

Speed Estimation

Voltage Calculation Current Regulation

Current measurement (d,q)  (a,b,c)

Motor

Speed

Ramp

Speed Regulation

Current/Torque Limitation

Synchronous Motor

 Torque curves

Control laws

Control law Type Code Performance Application Substitution

SVC U (BO) CTT =UUC Speed range 100, Torque at 0.5Hz

Material-handling Motors // Replacement

of ATV58

ATV58

SVC U (BO) +ENA

CTT=UUC ENA=Yes Energy saving

Unbalanced loads Oil pumps

ATV66 ENA ATV68

SVC I (BO) CTT=CUC

Speed Range 100, Torque at 0.5Hz, Dynamic, Braking while defluxed,

Hoisting Fast Machines

ATV58F BO ATV68

FVC (BF) CTT=FUC

Speed range 1000, Torque at 0Hz, Speed Precision 0.02%, Sway control

Hoisting Fast Machines Positioning Master/slave

ATV58F BF ATV68F

SVC I or FVC torque

CTT=CUC/FUC TSS=Yes

Torque control BO 15%, BF 5% Winders/Unwinders

ATV66F ATV68

U/F 2points CTT =UF2

Speed range 10, Torque at 5Hz, Fmax 1000Hz

Special motors High speed parallel, test

ATV58 special motor mode

U/F 5points CTT =UF5 Adaptable U/f profile Special motors

Special torque profiles New

Synchronous Motor SYN (BO) CTT=SYN

Open loop Speed Range 100,

Synchronous permanent magnet New Volts / Hertz

Voltage vector control

Current vector control

The motor control

I The motor control laws

III Protection against motor

overvoltage

IV Specific applications

Motor nameplate

performance of the motor control law.

and be followed by an auto-tune (TUN) to obtain optimization

protective functions

Motor Nameplate

• NSP – Nominal speed

Motor Nameplate

 Synchronous motor parameters

Motor nameplate

 Auto-tuning(TUN)

of the motor (except in the synchronous motor law).

compensated.

drops (RI compensation) and the optimization of the motor model for vector

control.

Motor nameplate

 Auto-tuning of asynchronous motors (TUN)

– RSM Cold stator resistance (Rs mOhms)

– IDM Nominal magnetizing current (Im A)

– LFM Leakage inductance (Ls µH)

– TRM Rotor time constant (tr mS)

– PPN Number of pole pairs (p)

– NSL Nominal motor slip (g Hz)

– RSA Cold stator resistance (Rs mOhms)

– IDA Nominal magnetizing current (Im A)

– LFA Leakage inductance (Ls 0.01 mH)

– TRA Rotor time constant (tr mS)

Motor nameplate

 Auto-tuning of synchronous motors (TUN)

– RSM stator resistance(tun)

– PHM flux of the permanent magnets (constant voltage)

– LDM d axis of the stator inductance

– LQM q axis of the stator inductance

– RSA stator resistance (cold)

– PHA permanent magnet flux (constant voltage)

– LDA d axis of the stator inductance

– LQA q axis of the stator inductance

Slip

 Adjustment of motor slip (SLP) :

motor control to compensate for the difference in rotor rotation speed between

no load and full load.

nameplate is not accurate.

Torque

F

An overestimation can cause instabilities

IR Compensation

 Adjustment if IR compensation (UFR) :

An overestimation can saturate the motor

Chopping Frequency

frequencies.

2 modes :

Chopping Frequency

strategy can be adapted according to the modulation factor.

automatically (level not settable)

a minimum of 2.5-4kHz (depending on the drive size)

frequency

Frequence de découpage

Taux de modulation

3-phase PWM

2-phase PWM

SFT = LF or HF

0.65 0.75

Phase Rotation

rotation to match forward/reverse run commands.

parameter

ATV71Motor control menu

Encoders

Encoder Configuration

(necessary to turn the motor).

overspeed and sway, catch on the fly (all control laws)

display of speed and monitoring for overspeed and sway

Recommendations

• Use a shielded cable containing 3 twisted pairs

• Tie the shield to ground at both ends.

• Use cables of sufficient size to limit the voltage drop.

• Maximum separation between the motor cables and encoder cables.

• The drive monitors the electrical and mechanical links to the encoder

ATV71The motor control laws

Speed Feedback Loop

Speed feedback loop

 Principal :

the ATV58 (FLG, STA) has been replaced.

non-specialists.

structures

applications.

PI speed feedback loop

 Settings « PI structure » SFC = 1

Speed Ramp Speed Reference

Speed feedback

+ -

Regulator

Torque current reference Limitation

SPG SIT =1/gI

Speed feedback loop PI

 Settings « PI structure » SFC = 1

Speed feedback loop IP

 Settings « IP structure » SFC = 0

constant).

toward the PI structure.

Speed Ramp Speed

reference

Speed feedback

+ -

Regulator

Torque current reference Limitation

SPG SIT =1/gI

Filter

SIT f(SFC)

Speed filter

constant

SFC SIT

Speed feedback loop IP

 Settings « IP structure » SFC = 0

ATV71Motor control menu

Current and torque limitation

Current limit

– CLI current limit

– CLI2 2nd current limit (activated by CLF=LIx)

normally the factory setting works.

and not settable)

2s

CLI

ATV58

60s 136%

OHF

OHF si SSB no Action like SSB

Current limit

and not settable)

Imax 150%

120%

100%

80%

continous overload

Torque limit

– TLIM limitation of motoring torque

– TLIG limitation of generating torque

– TAI= AIx limitation of torque by analog input

Limitation permanent

TLIM TLIG

Motoring Limit

Generating Limit

activation TLA=Lix

or yes

Limitation reference TAI=AIx

Internal Limitation Lowest

Limitation

Limitation

by analog input

activation TLC=Lix or yes

ATV71Motor control menu

Stopping modes, DC injection, Braking

Stop modes

•Upon a stop command the drive can stop in several programmable ways:

•Each stop mode can also be assigned to a logic input

Run command

Motor speed

STT=STN stop using ramp

required with vertical movement brake

STT=FST fast ramped stop

settable from 0 to 10 0 = minimum ramp

STT=NST free wheel stop

STT=DCI DC Injection

Automatic DC Injection at stop

• Upon a stop command DC injection is done as the speed approaches 0

• The function is activated by ADC, the injection time is set by TDC1

• The current level is set by SDC1

• If ADC = CT DC injection after TDC2 is permanent and the level is adjusted by SDC2

• In closed loop the injection level is automatically set be the drive and the time is set by TDC1

DC Injection by LI

• The function is activated by DCI=Lix,

• The DC injection is permanent when either the LI or the command word is activated.

• The current level is adjusted by IDC during TDI after which it is reduced to IDC2

• DCI has priority over the RUN command and keeps the motor stopped.

• Before injection the motor is automatically demagnetized

Motor speed

Current

DCI=Lix

TDI demagnetization

IDC

IDC2

RUN

Autoadaptation of the braking ramp

Autoadaptation of the braking ramp

Braking without resistors can be done using two modes :

• BRA = YES : Autoadaptation of the ramp (like the ATV58)

The ramp is frozen whenever the DC bus attains the level BRA

Controlled stop upon the loss of mains

In case of the loss of 3 phase power the stop mode of the drive can be configured.

TBS )

Maintain bus STP=MMS Mains

Bus DC

Speed

Level STP Level USF

Free wheel stop STP=FRP

Ramp stop STP=FRP

STM

Catch on the fly

applies the corresponding frequency to the output

Motor speed

Drive output

Speed estimate time delay

Free wheel stop + Run command

Detection of output phases opening

• When the detection of output phases opening is activated ( OPL=OAC) the output contactor can over and close at

any moment during the operation of the drive without shock and without tripping.

• The motor phase loss function is deactivated

• The drive locks itself out when it detects the opening of the contactor.

• When the contactor is closed catch on the fly is activated

Output contactor not

managed by the drive

Motor speed

Output Contactor

Speed estimation time delay

Run

Braking with a resistor

(the range depends on the size of the drive)

Balancing braking

• When many drives are connected to a common DC bus it is necessary the levels of braking activation are the same.

• This is to better share the braking power between the braking transistors.

• The BBA adjusts the activation level and a common hysteresis that is no longer dependent upon the DC bus

The motor control

I The motor control laws

II Motor control menu

overvoltage

IV Specific applications

ATV71Protection against motor overvoltage

Causes of overvoltage, solutions

Causes of motor overvoltages

generates rapid variations in voltage (dV/dt).

Causes of motor overvoltage

impedance matching between the motor and the motor cable.

modulation technique.

overvoltage dV/dt

l cable

PWM Voltage at Motor Terminals

-1500 -1000 -500 0 500 1000 1500

Causes of motor overvoltages

compatible with variable speed drives (class F).

4kW)

Remarks :

The dV/dt gradient is as bad for motor windings as the overvoltage itself (corona effect)

And very short wires can also be a problem because of low inductance and parasitic capacitance.

Causes of motor overvoltages

• An extract from IEC 60034-25 (electrical rotating machines) gives admissible overvoltage and dV/dt levels by motor type

A – motors up to 500V used with a variable speed drive

B – motors up to 600V used with a variable speed drive

C – motors not specified for use with variable speed drives (IEC60034-17)

C

Overvoltage kV

The admissible overvoltage is dependent upon the class of the motor insulation.

It also depends on the dV/dt, the higher the dV/dt the lower the admissible overvoltage.