Basics of an ac drive - with motor basics

Review of How Motor WorksMotor converts Electrical Energy to Rotating

Mechanical EnergyCoils placement in motor creates rotating,

magnetic field in statorRotating magnetic field cuts rotor bar and

induces current in rotorRotor current creates magnetic field on rotorAttraction of rotor to stator creates torque

and, hence, horsepower

AC Motor ReviewIn an AC Motor, speed varies by:

Motor Speed (rpm) = 120 x Frequency - SlipMotor Speed (rpm) = 120 x Frequency - Slip

# of Poles# of Poles

Since you can not change the number of poles in an AC motor,the frequency is changed to vary the speed.

Varying the Speed of an AC Motor

60 Hz30 Hz

1800(rpm)

900(rpm)

1800 = 60 x 120(rpm) 4

900 = 30 x 120(rpm) 4

AC Motor Review

In an AC motor, Torque Varies by:

T = K x ( )2 x I LineE

F

Where:K is a constantE is applied voltageF is input frequency I Line is motor current

AC Motor Review

Torque/Current RelationshipWhat you really need to know…...

• Current is roughly proportional to load torque

• The higher the load torque the higher the current

AC Motor Review

Horsepower of an AC motor can be determined by:

HP = Torque x Speed 5252

Where:Torque is in lb-ftSpeed is in RPM5252 is a constant

Motor nameplate Horsepower is achieved at Base RPM:Motor nameplate Horsepower is achieved at Base RPM:

HP = Torque * Speed / 5252HP = Torque * Speed / 5252

Torque

RPMBase Speed

100%

Horsep

ower

Constant Torque Constant Torque RangeRange

Constant Horsepower Constant Horsepower RangeRange

Note that motor nameplate Note that motor nameplate horsepower is only horsepower is only achieved at and above achieved at and above base speed, NOT BEFORE.base speed, NOT BEFORE.

Operation Above Base Speed

HP

AC Motor Review

IMPEDANCE

IMPEDANCE: Resistance of AC Current flowing through the windings of an AC Motor

NOTE: Impedance decreases as frequency decreases

Volts/Hertz RelationshipI = CurrentV = VoltageZ = Impedance

I = V Z

To reduce motor speed effectively:• Maintain constant relationship between current & torque• A constant relationship between voltage and frequency must be maintained

Volt/Hertz Relationship

60 Hz30 Hz

230 V

460 V

The AC variable speed drive controls voltage & frequencysimultaneously to maintain constant volts-per-hertz relationshipkeeping current flow constant.

AC DriveDC Bus

•Rectifier

- Converts AC line voltage to Pulsating DC voltage

• Inverter

- Changes fixed DC to adjustable AC

- Alters the Frequency of PWM waveform

• Intermediate Circuit (DC BUS)

- Filters the pulsating DC to fixed DC voltage

V

TT

V V V

T

AC Power Supply

Rectifier Inverter

M

Sine Weighted PWM

Bus Voltage Level

Sine Weighted PWM

PWM WAVEFORM

PWM waveform is a series PWM waveform is a series of repetitive of repetitive voltage pulsesvoltage pulses

1

3

+ DC Bus+ DC Bus

- DC Bus- DC Bus

VVLLLL @ Drive @ Drive

500 Volts / Div.500 Volts / Div.

Phase CurrentPhase Current10 Amps / Div.10 Amps / Div.

M2.00s Ch1 1.18V

Drive and Motor CompatibilityDrive and Motor CompatibilityDrive and Motor CompatibilityDrive and Motor Compatibility

VLL @ Drive500 Volts / Div.

VLL @ Motor500 Volts / Div.

Voltage Wave @Drive Output

Voltage Wave @ Motor Conduit Box

Potentially Damaging Voltage Peaks

How to Specify -- NEMA StandardsHow to Specify -- NEMA StandardsMG1-1993, Part 31.40.4.2MG1-1993, Part 31.40.4.2

How to Specify -- NEMA StandardsHow to Specify -- NEMA StandardsMG1-1993, Part 31.40.4.2MG1-1993, Part 31.40.4.2

10%

90%

Vpeak

t

Steady-state voltage100%

Voltage

V

dV

dt

V

t

Rise timeTime

Maximum of 1600 Volt Peaks

Minimum Rise Time of .1 Microseconds

GV3000/SEV/Hz OperationV/Hz Operation

At Base RPM or 60Hz, the Motor sees line input voltageAt Base RPM or 60Hz, the Motor sees line input voltage

OutputOutputFrequencyFrequencyBase FrequencyBase Frequency

6060

Output Output VoltageVoltage

Hz30

460460

230

115

15 90

Ratio @ 460VAC

= 7.67 V/Hz

0

GV3000/SEV/Hz Operation V/Hz Operation

OutputOutputFrequencyFrequencyBase FrequencyBase Frequency

60

Output Output VoltageVoltage

Hz30

460

230

115115

1515 90

Ratio @ 460VAC

= 7.67 V/Hz

0

At 25% of Base RPM or 15 Hz, Voltage & Frequency is 25%At 25% of Base RPM or 15 Hz, Voltage & Frequency is 25%

VECTOR DRIVE

Torque - ProducingCurrent (23.5 Amps)

MagnetizingCurrent

(8.5 Amps)

25.0AmpsFull

Load

Vector calculates Torque-Producing Current by knowing actual amps and magnetizing current.

GV3000/SEVector Control - Torque can be produced, as well as regulated even at “0” RPM

Motor Current is the Vector Sum of Torque & MagnetizingMotor Current is the Vector Sum of Torque & Magnetizing

Motor Current is the VECTOR SUM of Magnetizing Motor Current is the VECTOR SUM of Magnetizing & Torque Current,& Torque Current,

this is where the term VECTOR DRIVE is derivedthis is where the term VECTOR DRIVE is derived

Motor Current is the VECTOR SUM of Magnetizing Motor Current is the VECTOR SUM of Magnetizing & Torque Current,& Torque Current,

this is where the term VECTOR DRIVE is derivedthis is where the term VECTOR DRIVE is derivedTorque Current

Magnetizing Current

100%

Motor Current

90

Torque Current

Magnetizing Current

10%

Motor Current

90

GV3000/GV3000/SESE

Flux Vector DriveFlux Vector Drive - - simple diagram reviewsimple diagram review

A Vector Drive always regulates current

Encoder feedback provides rotor speed & position information for calculations Encoder feedback provides rotor speed & position information for calculations

L1L2

L3

Micro P

“LEM”Current Sensors

Motor

E

GV3000/GV3000/SESE

Sensorless Vector Control Sensorless Vector Control - - simple diagram reviewsimple diagram review

SVC estimates rotor speed & position to the stator field

A “Speed Estimator” calculates rotor speed & position to maintain 90° to the fieldA “Speed Estimator” calculates rotor speed & position to maintain 90° to the field

L1L2

L3 Motor

Micro P

( FVC + Speed Estimator )

“LEM”Current Sensors

150% Overload Operation to 0 RPM

120:1 Speed Range Speed Regulation

40:1, 0.5% Steady State20:1, 1.0% Dynamic

Dynamic Response100+ radian Speed Loop1000 radian Torque LoopTunable Speed PI gains

150% Overload Operation @ 0 RPM

1000:1 Speed Range Speed Regulation

100:1, 0.01% Steady State100:1, 0.5% Dynamic

Dynamic Response100+ radian Speed Loop1000 radian Torque LoopTunable Speed & Torque PI

gains

Sensorless Vector Flux Vector

INVERTER DUTY MOTORS

AC Drives regulate Motor Speed based on designed slipAC Drives regulate Motor Speed based on designed slip

NEMA Design ‘B” Motor w/ 3% Slip - Across the Line StartNEMA Design ‘B” Motor w/ 3% Slip - Across the Line Start

Operating Regionon AC Drives

Operating Regionon AC Drives

200%200%BDTBDT

FLTFLT100%100%

Base RPMBase RPM

SlipSlip

PUT

LRT

INVERTER DUTY MOTORS

Some motor frames are sized so that Some motor frames are sized so that just the surface area is suitable to just the surface area is suitable to

dissipate motor heat w/o the need of a dissipate motor heat w/o the need of a fan or blowerfan or blower

Some motor frames are sized so that Some motor frames are sized so that just the surface area is suitable to just the surface area is suitable to

dissipate motor heat w/o the need of a dissipate motor heat w/o the need of a fan or blowerfan or blower

Blowers may be added to Blowers may be added to motors to allow operation at low motors to allow operation at low speed including “0” RPM with speed including “0” RPM with

100% Torque continuous100% Torque continuous

Blowers may be added to Blowers may be added to motors to allow operation at low motors to allow operation at low speed including “0” RPM with speed including “0” RPM with

100% Torque continuous100% Torque continuous

GV3000/SE with“Inverter & Vector Duty” AC Motors

VXS MotorsBased on Reliance XEX Motor Designs

TENV, TEFC-XT and TEBC Enclosures Ideal for;

Positive Displacement Pumps and BlowersExtruders and MixersSteel and Converting Process lines

Standard Features;Encoder Mounting Provisions

Motor Shaft Tapped for Stub @ ODE Accessory Face @ ODE

Motor Winding Thermostats, 1/Phase10:1 to 1000:1 CT speed ranges w/o derating

GV3000/SE with“Inverter & Vector Duty” AC Motors

RPM-AC MotorsLaminated Steel, DC-style construction

DPFV, TENV, & TEBC enclosures Ideal for;

Extruder applicationsWeb processing & mill applicationsRetrofitting existing DC Drive & Motor systems

Standard Features;High torque to inertia ratiosEncoder Mounting ProvisionsMotor Winding Thermostats, 1/PhaseInfinite CT speed range, 0 RPM continuousCHp Range of 2:1 on TENV & TEBC FramesBase Speeds from 650 RPM to 3600 RPM

Speed RangeSpeed Range - Designed operating range of

an inverter duty motor

Example1800 rpm motor10:1 Speed Range = 180 -1800 (rpm)

CONSTANT TORQUE REGION

Inverter Duty Motors operate at 1/4th Base RPMInverter Duty Motors operate at 1/4th Base RPM

Speed / Torque Curve of an AC Drive & Inverter Duty MotorSpeed / Torque Curve of an AC Drive & Inverter Duty Motor

% TORQUE

0

10

20

30

40

50

60

70

80

90

100

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

TorqueTorque

TorqueTorque

HZ

Acceptable Regionfor Continuous Operation

CONSTANT HP REGION

CHp Operation above Base CHp Operation above Base

RPM is typically limited to 150%RPM is typically limited to 150%

Speed / Torque Curve of an AC Drive & Inverter Duty MotorSpeed / Torque Curve of an AC Drive & Inverter Duty Motor

% TORQUE

0

10

20

30

40

50

60

70

80

90

100

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

TorqueTorque

TorqueTorque

HZ

Torque above base RPM =

100%% Base RPM

CONSTANT TORQUE REGION

Vector Duty Motors operate at Vector Duty Motors operate at

““0” RPM w/ 100% Torque Cont.0” RPM w/ 100% Torque Cont.

Speed / Torque Curve of a Vector Drive & Vector Duty MotorSpeed / Torque Curve of a Vector Drive & Vector Duty Motor

% TORQUE

0

10

20

30

40

50

60

70

80

90

100

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

TorqueTorque

TorqueTorque

HZ

Acceptable Regionfor Continuous Operation

CONSTANT HP REGION

Some Vector Duty Motors can Some Vector Duty Motors can

provide CHp ( 2 * Base RPM )provide CHp ( 2 * Base RPM )

Speed / Torque Curve of a Vector Drive & Vector Duty MotorSpeed / Torque Curve of a Vector Drive & Vector Duty Motor

HZ

% TORQUE

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

TorqueTorque

TorqueTorque

0

10

20

30

40

50

60

70

80

90

100

96 102 108 114 120

Vector Duty Motors may haveCHP Ranges of

2 * Base Speed or moredepending on their design

Special motor & drive Special motor & drive designs can allow operation designs can allow operation

up to 8 * Base RPMup to 8 * Base RPM

Special motor & drive Special motor & drive designs can allow operation designs can allow operation

up to 8 * Base RPMup to 8 * Base RPM

Drive Terminology V/Hz DC Boost Accel / Decel Frequency Voltage HP Speed Skip & Bandwith Braking DB Regen Injection Coast Ramp

Restart Preset Jog Current Limit Analog / Digital Power Factor Harmonics Ride - Thru Speed Range Speed Regulation Frequency

Regulation Cogging Efficiency

Accel/DecelAcceleration Rate - Deceleration

Rate

Rate of change of motor speed.

Example:0 Speed - 1750 rpm 30 seconds

TIME

Frequency

100 %

30 sec

Full Voltage Bypass

GV3000/SE M

InputDisconnect

Switch

DriveBranchFusing

BypassDisconnect

Switch

BypassOption

Speed Regulation

How Much Will the Speed Change

Between No Load and Full Load?

Expressed as a Percentage

Speed Regulation

DC Voltage Boost

Voltage BoostVoltage Boost over prolonged operating periods may result in Voltage Boost over prolonged operating periods may result in overheating of the motor’s insulation system and result in overheating of the motor’s insulation system and result in premature failure.premature failure.

Unable to perform like DC, Unable to perform like DC,

the industry looks to Vector Controlthe industry looks to Vector Control

CAUTION: Motor Insulation Life is decreased by 50% for

every 10°C above the insulation’s temperature

capacity

CAUTION: Motor Insulation Life is decreased by 50% for

every 10°C above the insulation’s temperature

capacity

Critical Frequency

An Output Frequency of a Controller that

Produces a Load Speed at Which Severe

Vibration Occurs.

A Frequency at which Continuous Operation

is Undesirable

Skip Bandwith

0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8 9 10

Command Freq.

Output Freq

Skip Band

Skip Freq

AC Drive Inputs

Analog Inputs:• 0-10 VDC• ± 10 VDC• 4-20 mA

Digital Inputs:• Start• Stop• Reset• Forward/Reverse• Run/Jog• Preset Speeds

GV3000/GV3000/SESE

For Trip Free Deceleration if low to medium inertia loads

Trip Free Deceleration when enabled

High Bus Avoidance ( SVC & FVC )

SPEED

TIME

Snubber/Dynamic BrakingDC Bus

AC Power Supply

Rectifier Inverter

M

Braking Resistor

7th IGBT

• Snubber/Dynamic Braking

- Addition of Snubber Resitor Kit

- Dissipates excess energy to regulate

braking

- Regulator monitors DC bus voltage

- Signal sent to 7th IGBT

- Handles short term regenerative loads

- Less expensive than AC line regeneratiion braking

AC Regenerative Braking

AC Power Supply

• Severe Regenerative Braking

- Addition of AC Line Regeneration Module

- Monitors DC bus voltage

- Sends Excess voltage back to AC line

- Handles long term regenerative loads

Drive 1AC Line Regeneration

Module

Drive 2 Drive 2

- Run Multiple Drives off 1 Module

- Drives powered through DC bus instead

of through the Rectifier bridge

- Share regenerative energy between

motoring and regenerating drives

- Send energy back to AC Line instead of

dissipating as heat

Auto - Restart

How will the drive react after being shut down

by a fault condition? Will the drive resume

Running after the Fault condition is Cleared?

(Sometime restricted to certain Faults)

Preset Speeds

A Pre-Programmed Command Frequency

That can be activated via Mode

Select or Input Device

Current Limit

The ability of a drive to react to the increased current caused by momentarilyincreasing the load on the motor (Shock Loading) without tripping the drive on Overcurrent.

Power Loss Ride-Through

The Ability of a Controller to

sustain itself through a loss of

Input Line Voltage for a specific

period of time.

Operating Range ForVariable Frequency AC Drives