1. Review of How Motor Works
August 2000
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
(rpm)
1800 = 60 x 120
(rpm)
900
(rpm)
900 = 30 x 120
(rpm)
30 Hz
60 Hz

4. AC Motor Review In an AC motor, Torque Varies by:
August 2000
AC Motor Review
In an AC motor, Torque Varies by:
T = K x ( )2 x I Line E F
Where:
K is a constant
E is applied voltage
F is input frequency
I Line is motor current
Torque in an AC motor is calculated using a constant, the volts over the frequency squared, and the line current.
If you are running at a fixed speed and K is a constant, the Torque is directly proportional to the motor current. As it increases and decreases so does the torque.

5. Torque/Current Relationship What you really need to know…...
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. Horsepower of an AC motor can be determined by:
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 Range
Constant Horsepower Range
Torque
RPM
Base Speed
100%
Horsepower
Note that motor nameplate horsepower is only achieved at and above base speed, NOT BEFORE.

8. Operation Above Base Speed
August 2000
Operation Above Base Speed
Sure! if we maintain voltage and increase resistance, the current will begin to drop. We are now in the constant voltage mode of operation, and Torque begins to fall off. 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 = V Z
I = Current
V = Voltage
Z = Impedance
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
The AC variable speed drive
controls voltage & frequency
simultaneously to maintain
constant volts-per-hertz relationship
keeping current flow constant.
230 V
30 Hz
60 Hz

12. AC Drive M Inverter - Changes fixed DC to adjustable AC
August 2000
AC Drive
Rectifier
DC Bus
Inverter
AC Power Supply M
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

13. Sine Weighted PWM August 2000 Bus Voltage Level
The Sine weighted PWM voltage output to the motor looks like this. The frequency of the switch from positive to negative is determined by the drive based on the speed reference input, and the RMS or Average voltage value for that frequency is determined by the number and width of the pulses. If I vary or "Modulate" the pulse width, I vary the RMS Voltage to the motor.

14. Sine Weighted PWM August 2000
That voltage creates a current waveform in the motor that is very nearly a sine wave; certainly much closer to a true sine wave than the other technologies used in AC Drives. Here are the PWM waveforms. So by modulating or changing the Width of the voltage pulses and the frequency that those pulses create we create a very close approximation of a sinusoidal current waveform. The near sinusoidal nature of the current accomplishes two of our four goals; minimizing the low order harmonics ‑ you can see that the spikes are much smaller than in other technologies‑ and maximizing the transfer of power in the fundamental frequency.

15. PWM waveform is a series of repetitive voltage pulses1 3
+ DC Bus
- DC Bus
Drive
500 Volts / Div.
Phase Current
10 Amps / Div.
M2.00s Ch V
PWM waveform is a series
of repetitive voltage pulses

16. Drive and Motor Compatibility
August 2000
Drive and Motor Compatibility
Voltage Output V LL
@ Drive
500 Volts / Div.
@ Motor
Potentially Damaging Voltage Peaks
Voltage Motor Conduit Box
Scope traces from a 10 HP, 460 VAC VFD with 500 feet of cable between the VFD and the motor. The top wave shows the frequency at the drive output terminals. The bottom wave is the same wave at the motor terminals. An effect, called reflected wave, has raised the peak voltage at the motor terminals. 33

17. How to Specify -- NEMA Standards MG1-1993, Part 31.40.4.2
August 2000
How to Specify -- NEMA Standards MG1-1993, Part
Maximum of 1600 Volt Peaks
At a minimum, variable-speed AC moors should meet NEMA MG1 Part standards. That standard is depicted here.
They should also have a minimum CIV rating of 1,600 V at rated operating temperature for 460 VAC applications and should have a higher voltage rating for 575 VAC applications.
Always follow the lead length recommendations of the VFD manufacturer. Most have done extended testing to understand the reflected wave voltage amplitudes and dv/dt created by their products.
Use reactors and filters when the distance between the drive and the motor exceeds the manufacturers recommendations.
Use power-matched motor/drive packages that have been tested for compatibility in a wide range of operating conditions.
Minimum Rise Time of .1 Microseconds

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

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

20. VECTOR DRIVE Vector calculates Torque-Producing Current by
Current (23.5 Amps)
Magnetizing
Current
(8.5 Amps)
25.0
Amps
Full
Load
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 & Torque Current,
this is where the term VECTOR DRIVE is derived
Torque Current
Magnetizing Current
100%
Motor Current
90
Torque Current
Magnetizing Current
10%
Motor Current
90
Motor Current is the Vector Sum of Torque & Magnetizing

22. GV3000/SE Flux Vector Drive - simple diagram review
August 2000
GV3000/SE
Flux Vector Drive - simple diagram review
A Vector Drive always regulates current
“LEM”
Current Sensors L1 L2 L3
Motor E
Micro P
Encoder feedback provides rotor speed & position information for calculations

23. ( FVC + Speed Estimator )
August 2000
GV3000/SE
Sensorless Vector Control - simple diagram review
SVC estimates rotor speed & position to the stator field
“LEM”
Current Sensors L1
Motor L2 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
August 2000
Sensorless Vector
Flux Vector
150% Overload
Operation to 0 RPM
120:1 Speed Range
Speed Regulation
40:1, 0.5% Steady State
20:1, 1.0% Dynamic
Dynamic Response
100+ radian Speed Loop
1000 radian Torque Loop
Tunable Speed PI gains
150% Overload
0 RPM
1000:1 Speed Range
Speed Regulation
100:1, 0.01% Steady State
100:1, 0.5% Dynamic
Dynamic Response
100+ radian Speed Loop
1000 radian Torque Loop
Tunable Speed & Torque PI gains

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

26. INVERTER DUTY MOTORS
Blowers may be added to motors to allow operation at low speed including “0” RPM with 100% Torque continuous
Some motor frames are sized so that just the surface area is suitable to dissipate motor heat w/o the need of a fan or blower

27. GV3000/SE with “Inverter & Vector Duty” AC Motors
August 2000
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 ODE
Accessory ODE
Motor Winding Thermostats, 1/Phase
10:1 to 1000:1 CT speed ranges w/o derating
Optional Motor review slide

28. GV3000/SE with “Inverter & Vector Duty” AC Motors
August 2000
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
Optional Motor review slide

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

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

31. CHp Operation above Base RPM is typically limited to 150%
CONSTANT HP REGION
Speed / Torque Curve of an AC Drive & Inverter Duty Motor
100
Torque 90
% TORQUE 80
Torque 70 60
Torque above
base RPM =
100%
% Base RPM 50 40 30 20 10 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
% TORQUE 10 20 30 40 50 60 70 80 90
100 6 12 18 24 36 42 48 54 66 72 78 84
Torque HZ
Acceptable Region
for Continuous Operation
Vector Duty Motors operate at
“0” RPM w/ 100% Torque Cont.

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

34. Drive Terminology V/Hz DC Boost Accel / Decel Frequency Voltage HP
August 2000
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

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

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

37. Speed Regulation How Much Will the Speed Change
August 2000
Speed Regulation
How Much Will the Speed Change
Between No Load and Full Load?
Expressed as a Percentage
Speed Regulation, as a Percentage, is how much the speed will change between no load (Minimal slip) and Full Load (Maximum Slip).

38. Speed Regulation August 2000
Here's a curve for a standard Induction motor. 3% drop in speed. But a standard DC Drive typically has a 1‑2% speed Regulation, and, out of the box, a motion control drive provides .1% speed regulation. Why the difference?

39. August 2000
The difference is that most DC drives and all Motion Control Drives are what's known as closed loop. That means that some sort of feedback device attached to the motor feed speed information back to the drive for use in correcting any speed discrepancies. Open loop, like most AC Drives, means no such feedback exists, and the drive assumes that what it told the motor to do is actually being done.

40. DC Voltage Boost August 2000
That's where DC Boost comes in. In order to drop enough voltage across the inductance, we raise or boost the output voltage above what it would be normally, until there is enough voltage across the inductance to provide the necessary torque to turn the motor or "Break" the motor away. Once that voltage boost reaches the level that it would have been on the standard curve, the boost is turned off and operation proceeds as normal. We accomplish DC Boost by widening the pulses in the PWM waveform, creating a higher average voltage, and therefore more current.

41. Unable to perform like DC, the industry looks to Vector Control
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

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

45. Trip Free Deceleration when enabled
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
- Regulator monitors DC bus voltage
- Signal sent to 7th IGBT
- Handles short term regenerative loads
- Less expensive than AC line regeneratiion braking
Braking Resistor

47. AC Regenerative Braking
Drive 1
Drive 2
Drive 2
AC Power Supply
AC Line Regeneration Module
Severe Regenerative Braking
- Addition of AC Line Regeneration 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
- Monitors DC bus voltage
- Sends Excess voltage back to AC line
- Handles long term regenerative loads
- Run Multiple Drives off 1 Module

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
August 2000
Operating Range For Variable Frequency AC Drives
Now that we understand the technology of AC drives, we need to apply what we know to the characteristics we already know about the AC Motor. Only then can we know how the two will react together. Here is our standard speed torque curve for our NEMA B design motor. An AC Drive has a fixed Maximum Continuous Current limit which we have shown here as a dotted line representing 100% of drive current. In addition, most drives have an intermittent ability to supply current up to some additional level. We have chose the 150% level found in drives like the BUl Since the drive will be limiting the current available to the motor, we will no longer see the entire speed torque curve. We will not be able to get full breakdown torque from the motor and will not see 200% starting torque as we did across the line. Remember that 200% required 600% current. We are now limited to 150%. What we create then, is an operating range on the torque curve for a motor use with a drive. the area you see here is for full voltage at rated frequency. A motor controlled by an AC Drive will always operate somewhere in this range.