HSL Basic VFD Theory

8/4/2019 HSL Basic VFD Theory

1/33

SALES & SERVICE FOR

ABB AC VARIABLE SPEED DRIVES SOFT STARTERRS

DC VARIABLE SPEED DRIVES POWER QUALITY PRODUCTS

Variable Frequency Drives

Basic VFD Theory


2/33

SALES & SERVICE FOR



What is a VFD

( Variable Frequency Drive)

! Electrical / electronic piece ofequipment that varies the speed of a3 phase or AC motor.

! Also called .

! VSD ( Variable speed drive)

! ASD ( Adjustable speed drive)

!AFD ( Adjustable frequency drive)

! Inverter


3/33

SALES & SERVICE FOR



Basic VFD Operation

! Convert AC power to DC power.

!Filter DC power.

! Invert DC power to variable voltage

and variable frequency AC power.


4/33

SALES & SERVICE FOR



Voltage Source VFD

!"#$%

&'#()*+

,-.-'/01%)2+

*#++,3+4+3+".+

3+2$1)%03

4++,5).60$%#$%'/01%)2+)",'43+7$+".8.0"%301'*!2")1*

!"/+3%+3

#9:'510.6',!)23):

,!0,+

3+.%!4!+3:0%03

10),3+).%03


5/33

SALES & SERVICE FOR



Input

Line Capacitor

InverterRectifier

AC Motor

PWM Power Diagram


6/33

SALES & SERVICE FOR



Convert AC Input Power to DC

AC input power is rectified to DC through a six pulsediode bridge

DC voltage is equal to AC input voltage * 1.414 (root

2)!230 * 1.414 = 325

!460 * 1.414 = 650

!600 * 1.414 = 850

DC power is filtered and stored through a capacitor

bank called the DC bus


7/33

SALES & SERVICE FOR



Diode Rectifier


8/33

SALES & SERVICE FOR



Rectifier and Filter


9/33

SALES & SERVICE FOR



Power Factor


10/33

SALES & SERVICE FOR



Invert DC Power to Variable Voltage

and Frequency AC Power

! 2 IGBTs per output phase switch the positive and negativesides of the DC Bus utilising pulse width modulation

! IGBTs will have a characteristic rise time depending on itsgeneration and current rating

! Rise time is the time it takes the IGBT pulse when switched onto reach DC bus voltage level


11/33

SALES & SERVICE FOR



Insulated Gate Bipolar Transistors


12/33

SALES & SERVICE FOR



Inverter


13/33

SALES & SERVICE FOR



Full Voltage, 60 Hz PWM Waveform

Half Voltage, 30 Hz PWM Waveform

1.0

-1.0

1.0

-1.0

PWM Waveform


14/33

SALES & SERVICE FOR



Pulse Width Modulation


15/33

SALES & SERVICE FOR



Modulation of Waveform


16/33

SALES & SERVICE FOR



PWM Carrier Frequency


17/33

SALES & SERVICE FOR



Volts / Hz Ratio


18/33

SALES & SERVICE FOR

ABB AC VARIABLE SPEED DRIVES SOFT STARTERRSDC VARIABLE SPEED DRIVES POWER QUALITY PRODUCTS

Variable Voltage Variable Frequency

100

%

Amount

of Boost

Field Weakening

Region

Ou

tputVoltage

60HzOutput

Frequency


19/33

SALES & SERVICE FOR


VFD Summary

! VFD Varies the speed of an AC Motor

! Maximum output voltage = input

voltage

! V/Hz ratio is controlled throughout the

range up to 60 Hz.

! Torque decreases after 60Hz.

! Output wave form is Pulse Width

Modulated (PWM) .


20/33

SALES & SERVICE FOR


Application Types

! Variable Torque

! Constant Torque

! Constant Horsepower


21/33

SALES & SERVICE FOR


Variable Torque Curve

/0

1%)2

+;?

@?

??

A?

B? >?@?A? &? C?

*#++,';(D-=

C?

&?

B?

(03*+#09+3

%037$+

A??

E?

F?

G?


22/33

SALES & SERVICE FOR


Variable Torque

Affinity Laws:

! Flow is proportional to speed.

(Flow1/ Flow2) = (RPM1)/(RPM2)

! Pressure is proportional to the square of thespeed.

(Press1/ Press2) = (RPM1)2/ (RPM2)

2

! HP is proportional to the cube of the speed.

(HP1/ HP2) = (RPM1 )3/ (RPM2)

3


23/33

SALES & SERVICE FOR


Load Torque Proportional

To The Square of Speed

60 100

200%

100%

63%

Torque

(Typical

)

Continuous torque

capability

Speed in Hertz

Region of continuousoperation

Region of intermittent

operation

Peak torque

capability

Load torqueRequirement


24/33

SALES & SERVICE FOR


Variable Torque - Flow

Flow is proportional to speed.

(Flow1/ Flow2) = (RPM1) / (RPM2)

Flow RPM Second Second

Gallons/min RPM Flow

10000 1800 900 5000.00


25/33

SALES & SERVICE FOR


Variable Torque - Pressure

Pressure is proportional to the

square of the speed.

(Press1/ Press2) = (RPM1)2/ (RPM2)2

Pressure RPM Second Second

Lb/sq. in RPM Pressure (lb/sq. in)

1000 1800 3600 4000


26/33

SALES & SERVICE FOR


Variable Torque Horsepower

HP is proportional to the cube of the speed.

(HP1/ HP2) = (RPM1)3/ (RPM2)

3

Horsepower RPM Second SecondRPM Horsepower

10 3450 3000 6.58


27/33

SALES & SERVICE FOR


Variable Torque Applications

Irrigation Water Pumps

Down-hole Water Pumps

Submersible Water Pumps

Domestic Water Pumps

Centrifugal Sewage

Treatment Pumps

Centrifugal Fans

Blowers

Air Handling Units

Chillers


28/33

SALES & SERVICE FOR


Constant Torque

! Torque remains constant up to the motor basespeed.

! HP is proportional to the speed.


29/33

SALES & SERVICE FOR


Constant Torque Curve

/0

1%)2+

;


30/33

SALES & SERVICE FOR


Constant Torque Applications

Conveyors

Compressors

Positive Displacement Pumps

Crushers

Mixers

Elevators

Escalators

Etc.


31/33

SALES & SERVICE FOR


Constant Torque Load

60 100

200%

100%

63%

Torq

ue

(Typ

ical)

Continuous torquecapability

Speed in Hertz

Region of continuouso eration

Region of intermittenoperation

Load torquerequirement

Region of intermittentoperation

Peak torquecapability

60 100

200%

100%

63%

Torq

ue

(Typ

ical)

Continuous torquecapability

Speed in Hertz

egion of continuousperation


Load torquerequirement


Peak torquecapability


32/33

SALES & SERVICE FOR


Torque De-rating Due to

Motor Cooling

6 0 1 0 0

2 0 0 %

1 0 0 %

6 3 %

Fie ld w eaken ing reg ion

Peak torque capab i li ty

prov ided tha t the AC

dr ive has adeq uateover load capabi l i tyT

or

que

(Ty

pical)

C o n t i n u o u s t o r q u e

cap abi l i ty l imited

by m otor coo l ing

S p e e d i n H e r t z6 0 1 0 0

2 0 0 %

1 0 0 %

6 3 %

Fie ld w eaken in g reg ion

Peak torque capab i li ty

prov ided tha t the AC

dr ive has adeq uateover load capabi l i tyT

or

que

(Ty

pical)

C o n t i n u o u s t o r q u e

cap abi l i ty l imited

by m otor coo l ing

S p e e d i n H e r t z

T C B l & Ab 60


33/33

SALES & SERVICE FOR


Torque Curve Below & Above 60

Hz, Constant Torque V/F Ratio

%HIJKL';).':HMHI=

.HNOMPNM'%HIJKL':HQL'HR'0SLIPMTHN

@-?

*SLLQ

5POL A-B

(#

%HIJKLPNQ

(#

%HIJKL

%HIJKL';,.':HMHI=

(#

HSL Basic VFD Theory

Documents

Transcript of HSL Basic VFD Theory