Basics of an ac drive - with motor basics

1. Review of How Motor Works
Motor converts Electrical Energy to Rotating Mechanical
Energy
Coils placement in motor creates rotating, magnetic field in
stator
Rotating magnetic field cuts rotor bar and induces current in
rotor
Rotor current creates magnetic field on rotor
Attraction of rotor to stator creates torque and, hence,
horsepower

2. AC Motor Review
In an AC Motor, speed varies by:
Motor Speed (rpm) = 120 x Frequency - Slip
# of Poles
Since you can not change the number of poles in an AC motor,
the frequency is changed to vary the speed.

3. Varying the Speed
of an AC Motor
1800 1800 = 60 x 120
(rpm)
(rpm) 4
900 900 = 30 x 120
(rpm)
(rpm) 4
30 Hz 60 Hz

4. AC Motor Review
In an AC motor, Torque Varies by:
E 2
T = K x ( ) x I Line
F
Where:
K is a constant
E is applied voltage
F is input frequency
I Line is motor current

5. AC Motor Review
Torque/Current Relationship
What you really need to know…...
• Current is roughly proportional to load torque
• The higher the load torque the higher the current

6. AC Motor Review
Horsepower of an AC motor can be determined by:
HP = Torque x Speed
5252
Where:
Torque is in lb-ft
Speed is in RPM
5252 is a constant

7. Motor nameplate Horsepower is achieved at Base RPM:
HP = Torque * Speed / 5252
Constant Torque Constant Horsepower
Range Range
PM
R
Note that
motor na
horsepow meplate
er is only
achieved
at and ab
Horsepower
base spe ov
ed , NOT B e
EFORE.
d
ee
Sp
10 u e
0%
e
rq
as
To
B

8. Operation Above Base Speed
HP

9. AC Motor Review
IMPEDANCE
IMPEDANCE: Resistance of AC Current flowing
through the windings of an AC Motor
NOTE: Impedance decreases
as frequency decreases

10. Volts/Hertz Relationship
I = Current
V = Voltage I=V
Z = Impedance
Z
To reduce motor speed effectively:
• Maintain constant relationship between
current & torque
• A constant relationship between voltage and
frequency must be maintained

11. Volt/Hertz Relationship
460 V
The AC variable speed drive
controls voltage & frequency
230 V simultaneously to maintain
constant volts-per-hertz relationship
keeping current flow constant.
30 Hz 60 Hz

12. AC Drive
Rectifier DC Bus Inverter
AC Power Supply
M
V
V V V
T
T T
•Rectifier • Inverter
- Converts AC line voltage to Pulsating DC voltage - Changes fixed DC to adjustable AC
- Alters the Frequency of PWM waveform
• Intermediate Circuit (DC BUS)
- Filters the pulsating DC to fixed DC voltage

13. Sine Weighted PWM
Bus Voltage
Level

14. Sine Weighted PWM

15. PWM WAVEFORM
VLL @ Drive
500 Volts / Div.
+ DC Bus
1
- DC Bus
3
Phase Current
10 Amps / Div.
M2.00µs Ch1 1.18V
PWM waveform is a series
of repetitive voltage pulses

16. Drive and Motor Compatibility
Voltage Wave
VLL @ Drive @Drive Output
500 Volts / Div.
Potentially
Damaging
Voltage
Peaks VLL @ Motor
500 Volts / Div.
Voltage Wave
@ Motor
Conduit Box

17. How to Specify -- NEMA Standards
MG1-1993, Part 31.40.4.2
Maximum of 1600 Volt Peaks
Vpeak
Voltage
Steady-state voltage
100%
90%
∆
V
dV ∆
V
=
dt ∆
t
10%
∆
t
Time
Rise time
Minimum Rise Time of .1 Microseconds

18. GV3000/SE
V/Hz Operation
Output 460
Voltage
Ratio @ 460VAC
= 7.67 V/Hz
230
115
Hz
0 15 30 60 90 Output
Base Frequency Frequency
At Base RPM or 60Hz, the Motor sees line input voltage

19. GV3000/SE
V/Hz Operation
Output 460
Voltage
Ratio @ 460VAC
= 7.67 V/Hz
230
115
Hz
0 15 30 60 90 Output
Base Frequency Frequency
At 25% of Base RPM or 15 Hz, Voltage & Frequency is 25%

20. VECTOR DRIVE
Magnetizing
Current 25.0
(8.5 Amps) Amps
Full
Load
Torque - Producing
Current (23.5 Amps)
Vector calculates Torque-Producing Current by
knowing actual amps and magnetizing current.

21. GV3000/SE
Vector Control - Torque can be produced, as well as regulated even at “0” RPM
Motor Current is the VECTOR SUM of Magnetizing
Motor Current is the VECTOR SUM of Magnetizing
& Torque Current,
& Torque Current,
100%
this is where the term VECTOR DRIVE is derived
this is where the term VECTOR DRIVE is derived
Torque
Current
Motor Torque
Current Current Motor
10% Current
90° 90°
Magnetizing Current Magnetizing Current
Motor Current is the Vector Sum of Torque & Magnetizing

22. GV3000/SE
Flux Vector Drive - simple diagram review
A Vector Drive always regulates current
“LEM”
Current
Sensors
L1
L2 Motor
L3
E
Micro P
Encoder feedback provides rotor speed & position information for calculations

23. GV3000/SE
Sensorless Vector Control - simple diagram review
SVC estimates rotor speed & position to the stator field
“LEM”
Current
Sensors
L1
L2 Motor
L3
Micro P
( FVC + Speed Estimator )
A “Speed Estimator” calculates rotor speed & position to maintain 90° to the field

24. Sensorless Vector Flux Vector
 150% Overload  150% Overload
 Operation to 0 RPM  Operation @ 0 RPM
 120:1 Speed Range  1000:1 Speed Range
 Speed Regulation  Speed Regulation
 40:1, 0.5% Steady State  100:1, 0.01% Steady State
 20:1, 1.0% Dynamic  100:1, 0.5% Dynamic
 Dynamic Response  Dynamic Response
 100+ radian Speed Loop  100+ radian Speed Loop
 1000 radian Torque Loop  1000 radian Torque Loop
 Tunable Speed PI gains  Tunable Speed & Torque PI gains

25. INVERTER DUTY MOTORS
NEMA Design ‘B” Motor w/ 3% Slip - Across the Line Start
BDT
200%
Operating
LRT
Region
on AC
PUT
Drives
100% FLT
Slip
Base RPM
AC Drives regulate Motor Speed based on designed slip

26. INVERTER DUTY MOTORS
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 continuous
100% Torque continuous
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 blower
fan or blower

27. GV3000/SE with
“Inverter & Vector Duty” AC Motors
VXS Motors
 Based on Reliance XEX Motor Designs
TENV, TEFC-XT and TEBC Enclosures
 Ideal for;
Positive Displacement Pumps and Blowers
Extruders and Mixers
Steel and Converting Process lines
 Standard Features;
Encoder Mounting Provisions
Motor Shaft Tapped for Stub @ ODE
Accessory Face @ ODE
Motor Winding Thermostats, 1/Phase
10:1 to 1000:1 CT speed ranges w/o derating

28. GV3000/SE with
“Inverter & Vector Duty” AC Motors
RPM-AC Motors
 Laminated Steel, DC-style construction
 DPFV, TENV, & TEBC enclosures
 Ideal for;
 Extruder applications
 Web processing & mill applications
 Retrofitting existing DC Drive & Motor systems
 Standard Features;
 High torque to inertia ratios
 Encoder Mounting Provisions
 Motor Winding Thermostats, 1/Phase
 Infinite CT speed range, 0 RPM continuous
 CHp Range of 2:1 on TENV & TEBC Frames
 Base Speeds from 650 RPM to 3600 RPM

29. Speed Range
Speed Range - Designed operating range of an inverter duty
motor
Example
1800 rpm motor
10:1 Speed Range = 180 -1800 (rpm)

30. CONSTANT TORQUE REGION
Speed / Torque Curve of an AC Drive & Inverter Duty Motor
100
Torque
90
% 80
Torque
T 70
O 60
R 50
Q 40
Acceptable Region
U 30
for Continuous Operation
E 20
10
0
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90
HZ
Inverter Duty Motors operate at 1/4th Base RPM

31. CONSTANT HP REGION
Speed / Torque Curve of an AC Drive & Inverter Duty Motor
100
Torque
90
% 80
Torque
T 70
O 60
Torque above
R 50
base RPM =
Q 40
100%
U 30
% Base RPM
E 20
10
0
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90
HZ
CHp Operation above Base
RPM is typically limited to 150%

32. CONSTANT TORQUE REGION
Speed / Torque Curve of a Vector Drive & Vector Duty Motor
100
Torque
90
% 80
Torque
T 70
O 60
R 50
Q 40
Acceptable Region
U 30
for Continuous Operation
E 20
10
0
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90
HZ
Vector Duty Motors operate at
“0” RPM w/ 100% Torque Cont.

33. CONSTANT HP REGION
Speed / Torque Curve of a Vector Drive & Vector Duty Motor
100
Special motor & drive
Special motor & drive
90
designs can allow operation
designs can allow operation
% 80 up to 8 * Base RPM
up to 8 * Base RPM
T 70
O 60 Torque
R 50 Torque
Q 40
Vector Duty Motors may have
U 30 CHP Ranges of
E 20 2 * Base Speed or more
10
depending on their design
0
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120
HZ
Some Vector Duty Motors can
provide CHp ( 2 * Base RPM )

34. Drive Terminology
 V/Hz  Restart
 DC Boost  Preset
 Accel / Decel  Jog
 Frequency  Current Limit
 Voltage  Analog / Digital
 HP  Power Factor
 Speed  Harmonics
 Skip & Bandwith  Ride - Thru
 Braking  Speed Range
 DB  Speed Regulation
 Regen  Frequency Regulation
 Injection  Cogging
 Coast  Efficiency
 Ramp

35. Accel/Decel
Acceleration Rate - Deceleration Rate
 Rate of change of motor speed.
100 %
Example:
Frequency 0 Speed - 1750 rpm 30 seconds
30 sec
TIME

36. Full Voltage Bypass
Drive Bypass
Branch Disconnect
Fusing Switch
GV3000/SE M
Input
Disconnect
Switch
Bypass
Option

37. Speed Regulation
How Much Will the Speed Change
Between No Load and Full Load?
Expressed as a Percentage

38. Speed Regulation

40. DC Voltage Boost

41. Voltage Boost
Voltage Boost over prolonged operating periods may result in
overheating of the motor’s insulation system and result in
premature failure.
CAUTION: Motor Insulation
Life is decreased by 50% for
every 10°C above the
insulation’s temperature
capacity
Unable to perform like DC,
the industry looks to Vector Control

42. 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

43. Skip Bandwith
60
50
40
Command Freq.
Output Freq
30
Skip Band
Skip Freq
20
10
0
0 1 2 3 4 5 6 7 8 9 10

44. AC Drive Inputs
Analog Inputs: Digital Inputs:
• 0-10 VDC • Start
• ± 10 VDC • Stop
• 4-20 mA • Reset
• Forward/Reverse
• Run/Jog
• Preset Speeds

45. GV3000/SE
High Bus Avoidance ( SVC & FVC )
 For Trip Free Deceleration if low to medium inertia loads
SPEED
TIME
Trip Free Deceleration when enabled

46. Snubber/Dynamic Braking
Rectifier DC Bus Inverter
AC Power Supply
M
• Snubber/Dynamic Braking
- Addition of Snubber Resitor Kit 7th IGBT
- Dissipates excess energy to regulate
braking
Braking Resistor
- Regulator monitors DC bus voltage
- Signal sent to 7th IGBT
- Handles short term regenerative loads
- Less expensive than AC line regeneratiion braking

47. AC Regenerative Braking
AC Power Supply
AC Line Drive 1 Drive 2 Drive 2
Regeneration
Module
• Severe Regenerative Braking
- Drives powered through DC bus instead
- Addition of AC Line Regeneration Module
- Monitors DC bus voltage of through the Rectifier bridge
- Sends Excess voltage back to AC line - Share regenerative energy between
- Handles long term regenerative loads motoring and regenerating drives
- Run Multiple Drives off 1 Module - Send energy back to AC Line instead of
dissipating as heat

48. 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)

49. Preset Speeds
A Pre-Programmed Command Frequency
That can be activated via Mode
Select or Input Device

50. Current Limit
The ability of a drive to react to
the increased current caused by momentarily
increasing the load on the motor (Shock Loading)
without tripping the drive on Overcurrent.

51. 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.

52. Operating Range For
Variable Frequency AC Drives