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Successful VFD Application
www.tmeic.com Slide 1
How to Be Successful
In VFD Application
How to Be Successful in
Drive Application
Bill Horvath, PE
TMEIC Corporation
Roanoke, VA 24153
Mining Electrical Maintenance Association [MEMSA]
June 2015 Technical Symposium
Clearwater, Florida
Successful VFD Application
www.tmeic.com Slide 2
How to Be Successful
In VFD Application
How to Be Successful in
Drive Application
Successful VFD Application
www.tmeic.com Slide 3
How to Be Successful
In VFD Application
MV AC VFD and Motor System
Successful VFD Application
www.tmeic.com Slide 4
How to Be Successful
In VFD Application
VFD System Considerations
Must consider the whole system in which the
VFD will work
From Utility to finished product or process
Consider environment
Consider effects on utility
Consider the needs of the load
Consider the effect on motors and load
Successful VFD Application
www.tmeic.com Slide 5
How to Be Successful
In VFD Application
A VFD Pictorial Overview
Successful VFD Application
www.tmeic.com Slide 6
How to Be Successful
In VFD Application
VFD Overall Success Factors 1. Minimum first cost, including installation
2. Maximum long-term payback.
3. Good match to process & loads.
4. Long equipment life.
5. Ease of use for operators & technicians.
6. Minimum impact on nearby equipment.
7. Easy to maintain & repair.
Successful VFD Application
www.tmeic.com Slide 7
How to Be Successful
In VFD Application
Relation to Overall Success Factors
Application factors can be grouped
into two major areas:
Electrical/Load Application Factors
Design & Installation Factors
Successful VFD Application
www.tmeic.com Slide 8
How to Be Successful
In VFD Application
Electrical/Power Application Factors
Continuous kW or HP & duty cycle
Torque & Power Overload Requirements
Load factors: CT, VT, CHP, regenerative,
non-regenerative.
Drive and Motor Voltage
Power system compatibility, efficiency
Successful VFD Application
www.tmeic.com Slide 9
How to Be Successful
In VFD Application
Solution Process Start At Ends
and Work Towards the Middle
#2 - Define the
power system
and requirements
#1 - Define the
process loads
and duty cycle
#3
Determine best
drive solution!
Successful VFD Application
www.tmeic.com Slide 10
How to Be Successful
In VFD Application
Know Your Drive Load
Torque loading vs RPM
Regen vs non regen
Continuous operating
points needed
Peak torque needed to
break load away
Load inertia
Speed-time ramps for
accel & decel
Motor
Drive type
Motor thermal rating, Drive
size
Motor starting/breakdown
torque rating, Drive Type
& OL Rating
Drive Tuning & stability
Drive settings
LOAD FACTOR AFFECTS
Successful VFD Application
www.tmeic.com Slide 11
How to Be Successful
In VFD Application
Conveyor or Mill Loading
Typical Induction Motor Char on 60 Hz power
TO
RQ
UE
FREQ, SPEED
BREAKAWAY
TORQUE
Successful VFD Application
www.tmeic.com Slide 12
How to Be Successful
In VFD Application
Conveyor or Mill Loading
Typical Induction Motor Char on 60 Hz power
TO
RQ
UE
FREQ, SPEED
BREAKAWAY
TORQUE
VFD CONTROLLED MOTOR -
ENOUGH TORQUE ACROSS THE RANGE
A
B C
D
Maximum
Continuous
Power Point
Max
Continuous
Power
Intermediate
Continuous
Power Points
Successful VFD Application
www.tmeic.com Slide 13
How to Be Successful
In VFD Application
Continuous Power Requirements
Continuous Power
Needs Set Size of Power Delivery
Transformers
Drive and internal
transformer
Motor
Gearbox
Successful VFD Application
www.tmeic.com Slide 14
How to Be Successful
In VFD Application
Peak Torque Requirements
Peak Torque Needs
Affect the Size of Inverter [Switches,
diodes, capacitors]
Sensors
Motor
Gearbox
Successful VFD Application
www.tmeic.com Slide 15
How to Be Successful
In VFD Application
Duty Cycle Example
Horsepower = Torque x RPM / 5252
High torque at low speed = low HP
0
2.0
1.0
0
1.0
0.5
60
Torque
Speed [RPM]
Horsepower
0
1.0
0.5
120 180 240 240 300 360
TIME IN SECONDS >
One duty cycle >
Successful VFD Application
www.tmeic.com Slide 16
How to Be Successful
In VFD Application
Duty Cycle Calculations
1. Gather information on load torque, HP and speed vs. time
2. Lay out in time sequence
3. Break up into segments
4. Square HP values and get HP2 sec values
5. Sum and take square root
6. Result is RMS HP for motor, drive, and power delivery sizing
Successful VFD Application
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How to Be Successful
In VFD Application
Drive Ratings and Torques
Variable Torque [VT] ratings usually include 110 -115% OL rating
for 60 seconds when starting from rated Temp
Constant Torque [CT] rating usually includes 150% OL rating for
60 seconds when starting from rated Temp.
Successful VFD Application
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How to Be Successful
In VFD Application
Variable Torque Curve
0
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
100.00%
% Speed
Load Torque Varies as the Square of the Speed
Motor Horsepower varies as the Cube of the Speed
Successful VFD Application
www.tmeic.com Slide 19
How to Be Successful
In VFD Application
Drive Ratings and Torques
Variable Torque [VT] ratings usually include 110 -115% OL rating
for 60 seconds when starting from rated Temp
Constant Torque [CT] rating usually includes 150% OL rating for
60 seconds when starting from rated Temp.
Successful VFD Application
www.tmeic.com Slide 20
How to Be Successful
In VFD Application
Torque Curves Variable vs Constant Torque
Characterized load curves that looks like:
C o n s t a n t T o r q u e L o a d , E x a m p l e 2
C o n s t a n t T o r q u e L o a d , E x a m p l e 1
R P M - - >
L o
a d
T o
r q u
e
T h e o r e t i c a l M o t o r C a p a b i l i t y 1 0 0 % L o a d P o i n t ,
N P R P M , S i n e w a v e p o w e r
i m c a p a b 1 . d r w J u n e 4 , 9 8
Successful VFD Application
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How to Be Successful
In VFD Application
Load mass or inertia requires torque in opposite direction of RPM
Torque x RPM = Negative
Power Flows from motor (now acting as a generator)
Examples:
Stopping a fan
Downhill conveyor
Lowering a load on a crane
Drive converter design must accept power in reverse direction
Active front end
Diode fed will not regenerate
Motoring
Motoring
Regen
(+) Torque
(-) Torque
(+)
RP
M
(-)
RP
M
Q3
Q1 Q2
Q4 Regen
S T
S T
S T
S T
Regenerative Loads
Successful VFD Application
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How to Be Successful
In VFD Application
Weve looked at the process loads, now lets
look at how to power the loads . . . . . . . .
#2 - Define the
power system
and requirements
#1 - Define the
process loads
and duty cycle
#3
Determine best
drive solution!
Successful VFD Application
www.tmeic.com Slide 23
How to Be Successful
In VFD Application
Power System Compatibility Including
Power distribution (available
utilization voltages)
Protection.
Harmonics limits.
Power factor control.
Efficiency.
Successful VFD Application
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How to Be Successful
In VFD Application
Power System Compatibility
Breakers, transformers, and cable must be rated to carry full kVA &
harmonics. Selecting higher capacity utilization voltages may
reduce drives impact on the customers power grid.
Transformers need to be drive isolation rated with proper
considerations for the drive type.
Protective devices & settings consider harmonics and drive characteristics.
Successful VFD Application
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How to Be Successful
In VFD Application
Power Line Harmonics
Harmonics are voltages and currents at frequencies that are multiples of utility power frequency.
Harmonic currents are drawn by loads such as drives, computers and ballasts that take their power in non-sine-wave format. These are so-called non-linear loads.
-1.5
-1
-0.5
0
0.5
1
1.5
0 120 240 360
Fundamental, 5th and 7th Harmonics
Sum
Fundamental
7th5th
Successful VFD Application
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How to Be Successful
In VFD Application
Power Line Harmonics
Harmonics from drives can excite other parts of the system and
cause damage
Over-voltages on un-tuned PF caps
High currents due to parallel resonance
Equipment problems may be minimized by reducing
harmonics using:
Filters & Tuned PF correction.
Multi-pulse rectifier drives.
Successful VFD Application
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How to Be Successful
In VFD Application
IEEE 519-1992 Table 10.3 ITDD Limits
Maximum Harmonic Curent Distortion in % of I-Load
Isc to I-load
Ratio h < 11
h = 11
to
Successful VFD Application
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How to Be Successful
In VFD Application
Power System & Drive Efficiency
Drive itself is typically 98% or more efficient
With all fans, transformers, etc, efficiencies of 96-
97% are common
Efficiency impact of drive varies with speed
Efficiency effect of the drive can be eliminated
at full speed by synchronous bypass.
Successful VFD Application
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How to Be Successful
In VFD Application
Example Efficiency Data DB5i MV, Including Transformers & Fans
Calculated Dura-Bilt5 MV Inverter Performance,
500 HP Constant Torque Load
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0% 20% 40% 60% 80% 100%
Speed, %
PU
Ou
tpu
t o
r P
U P
F o
r P
U E
ffic
Load HP Output
Efficiency, includingauxil
True Power Factor[kw/kva]
Dura-Bilt5 MV Efficiency Testing Typical Results
25 50 75 100
25 89.5 94 96 97
50 93.5 95 96.5 97
75 94 95.5 96 97
100 93 94.5 96 96.5
DATA ABOVE TAKEN FROM 800 KVA FRAME TESTING, May 2002,
ON DYNO LOAD - TYPICAL, NOT GUARANTEED
PERCENT of top SPEED
PE
RC
EN
T O
F
FU
LL
LO
AD
Efficiencies in
Italic, expressed
in %
Successful VFD Application
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How to Be Successful
In VFD Application
Weve defined the process loads and available
power, now whats the best solution?????
#2 - Define the
power system
and requirements
#1 - Define the
process loads
and duty cycle
#3
Determine best
drive solution!
Successful VFD Application
www.tmeic.com Slide 31
How to Be Successful
In VFD Application
MV vs LV AC Drives: Cost Factors of Various Configurations
MV drive $ / HP decreases with HP
Harmonic content can be important:
MV data is 24 pulse TMGE DB5i MV
LV data is GE-Fuji AF300 P11
Installed cost must be considered
MV vs LV AC Drives
Budgetary $ per HP
vs HP
0.0
110.0
220.0
330.0
440.0
500.0
0 500 1000 1500
Horsepower
Bu
dg
eta
ry
$ p
er
Ho
rsep
ow
er
LV 6-Pulse w/o Transformer
MV 4160 v 24-Pulse DB5i
LV 6-Pulse w/8% Mirus filt
LV 18 pulse incl transf
Successful VFD Application
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How to Be Successful
In VFD Application
Drive Design For Reliability
Minimum parts fewest power components, and simplest firing circuits
No Weak links like marginally rated electrolytic caps
Conservatively rated, fully qualified components
Quality built in not burn-in tested
Quality tracked
Successful VFD Application
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How to Be Successful
In VFD Application
Drive Output Voltage & Motor Application
Why Pick LV [250 HP
Many users select MV over 500 HP.
Successful VFD Application
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How to Be Successful
In VFD Application
Some MV vs. LV Conclusions
For drives > 1000 HP, MV makes sense
For long cable runs, MV makes sense
For drives < 500 HP, LV makes sense.
If low power system harmonics are required, LV filter or multi-pulse
cost adders can favor MV over LV.
In the range 500 to 1000 HP the various application & installation
factors apply.
Final choice may boil down to user preference.
Successful VFD Application
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How to Be Successful
In VFD Application
Weve selected how to power our process, now lets control it and
keep it running!!!!!!!
Successful VFD Application
www.tmeic.com Slide 36
How to Be Successful
In VFD Application
Speed & Torque Control Requirements
Each application is unique Simple, free-standing pumps
Complex e.g. sync to utility, multiple motors per drive, multiple drives on same load
Process control usually 4-20 Ma for speed
Go Tachless if possible Precise speed control rare with MV
drives and high KW level drives
High load torques [>150%] may require tach
Successful VFD Application
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How to Be Successful
In VFD Application
Operator Control and Communication
Interface with larger process controls for operator
Simple start-stop contacts
More complex HMI
Process equipment controls system PLC
LAN communication of drive status if/as needed to plant PLC or DCS
Plan for remote diagnostics capability
Successful VFD Application
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How to Be Successful
In VFD Application
Integrated Trend Window
Drag and drop variables
Real time trending or
archiving to buffer for
historical trending
Auto scaling
Zoom in/out function
Different views by using
variable hide feature
Analyze specific time with
cross hair
Frequency-based analysis of
trend with fast Fourier
transform function
Easy to Understand Data Structure: Drive parameters
and variables in tree
structure
Animated Block Diagrams
Drive Toolbox Interface
Important for Drive Success
Successful VFD Application
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How to Be Successful
In VFD Application
Successful VFD Application
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How to Be Successful
In VFD Application
Successful Drive Application: Electrical Factors & How They Relate to Success
Successful VFD Application
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How to Be Successful
In VFD Application
Design and Installation Factors Relating to Successful Application
Physical Environment of drive
Drive Design and Reliability
Motor Installation & Connections
Speed & Torque Control Requirements
Operator Control and Communication
Design for Maintainability and Installation
Successful VFD Application
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How to Be Successful
In VFD Application
Environment MV Equipment
Equipment is designed to be installed in a
relatively clean, dry environment
Operation
0 to 40 or 50 C with a relative humidity of 95%
maximum, non-condensing.
Storage
Equipment is generally designed for a non-operating
(storage) temperature range
of 25 C to 70 C.
Successful VFD Application
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How to Be Successful
In VFD Application
Environment at Location
Altitude: De-rate current rating 3% per 1000 ft above 3000 feet. May have to de-rate voltage for very high altitudes.
Temperature Derate (air cooled drive): 1.5% per degree C above base rating [usually 40C] up to max [usually 50 C].
Drives put out heat must be removed or vented to outside.
High-power drives are usually liquid cooled with remote heat exchangers.
In the presence of corrosives or dust or water - pick appropriate enclosure. [be careful of cooling!].
Successful VFD Application
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How to Be Successful
In VFD Application
Facility Readiness
Foundation Plans
Pads for transformers and switchgear
Pads or columns for Equipment houses
Off loading equipment
Cranes, fork-trucks
Personnel protection
Fences, signs, railings
Training
Successful VFD Application
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How to Be Successful
In VFD Application
Foundation Planning
Successful VFD Application
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How to Be Successful
In VFD Application
You can never have too big of a crane.says
the crane salesman !!!
Successful VFD Application
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How to Be Successful
In VFD Application
Site Planning
Successful VFD Application
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How to Be Successful
In VFD Application
Equipment House Issues
Placing Drives in Houses Dont Forget :
Drives sometimes come in many parts
some assembly required wiring, plumbing, etc.
Auxiliary power and cooling must be wired
How can drive be handled? Roll, fork, etc.
Placement must allow access and meet codes
Door swing, voltage clearance, cable termination, removable panels
Equipment heat dissipation (sensible heat) plus humidity
removal (latent heat) must be considered
May require redundancy in cooling system to give best up-time
on system
Successful VFD Application
www.tmeic.com Slide 49
How to Be Successful
In VFD Application
Cables From VFD to Motors
Drives themselves are usually tolerant of most cable types & methods
BUT, Cabling affects EMI radiation or motor.
Cables > 500 meters need special attention [cable capacitance]
Successful VFD Application
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How to Be Successful
In VFD Application
Most Ideal Cable for PWM Inverter Use
Most critical for LV drives, much less critical for MV Drives
Continuous, Corrugated, welded aluminum armor, with 3 symmetrical ground conductors.
Minimizes EMI / Radiated noise
Minimizes common mode volts at bearings
Example PWM cable manufacturers:
LV - Annixter/BICC Philsheath
LV- Rockbestos Supernant Gardex CC
MV Okonite C-L-X Type MV-90 or MV-105
MV Amercable MM-VFD More flexible Bronze armor shield
First Choice 3 Phase Conductors 3 Symmetrical Grounds 1 Overall Shield/Armor
Successful VFD Application
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How to Be Successful
In VFD Application
Example Okonite
C-L-X MV-105
[8-15 kv]
3 Symmetric
Grounds
Continuous
Successful VFD Application
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How to Be Successful
In VFD Application
Example
Amercable MMV-
VFD [8-15 kv]
Successful VFD Application
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How to Be Successful
In VFD Application
Example General
Cable MV-Rig
[8-15 kv]
Successful VFD Application
www.tmeic.com Slide 54
How to Be Successful
In VFD Application
PWM Motor Cabling 3-ground example
Minimizes injected ground current into Pcom bus for electronics reliability.
Reduces bearing currents from common mode currents.
Minimizes cross talk induced voltages on adjacent cables for noise immunity and safety sake.
Inverter to Motor cabling example: 3 grounds and continuous armor shield
P c o m m
C O N T R O L C I R C U I T S
P c o m m
S H I E L D
N E C
G R O U N D S
I N D U C T I O N
M O T O R
N E C F R A M E C O N N E C T I O N
P c o m m C o n n e c t i o n
C o n d u i t
B o x
E n c l o s u r e E x i t p l a t e
ARMOR
Successful VFD Application
www.tmeic.com Slide 55
How to Be Successful
In VFD Application
PWM Motor Cabling 1-ground conductor example
Minimizes injected ground current into Pcom bus for electronics reliability.
Minimizes cross talk induced voltages on adjacent cables for noise immunity and safety sake.
Inverter to Motor cabling example: 1 ground and continuous armor shield
P c o m m
C O N T R O L C I R C U I T S
P c o m m
S H I E L D
N E C
G R O U N D
I N D U C T I O N
M O T O R
N E C F R A M E C O N N E C T I O N
P c o m m C o n n e c t i o n
C o n d u i t
B o x
E n c l o s u r e E x i t p l a t e
ARMOR
Successful VFD Application
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How to Be Successful
In VFD Application
Motor-Drive Cable Methods And Tradeoffs
Successful VFD Application
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How to Be Successful
In VFD Application
Drive Cabling Summary
For LV Drives, use triple-ground cable with overall extruded continuous armor, grounded as shown.
For MV NPC drives, use either single or triple-ground cable, with overall extruded continuous armor cable, grounded as shown.
Other cables may not cause trouble, but some risk is involved.
New NEC 2005 requires shielded cables!
Successful VFD Application
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How to Be Successful
In VFD Application
Successful VFD Application
www.tmeic.com Slide 59
How to Be Successful
In VFD Application
Successful Drive Application: Design & Installation Factors & Relation to Success
Successful VFD Application
www.tmeic.com Slide 60
How to Be Successful
In VFD Application
Drive Applications
Successful VFD Application
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How to Be Successful
In VFD Application
Thanks!
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