# Variable Frequency Drives

```Application Types
•
Variable Torque
•
Constant Torque
Variable Torque
Affinity Laws:
• Flow is proportional to speed.
(Flow1 / Flow2) = (RPM1)/(RPM2)
• Pressure is proportional to the square of the
speed.
(Press1 / Press2) = (RPM1)2 / (RPM2)2
• HP is proportional to the cube of the speed.
(HP1 / HP2) = (RPM1 )3/ (RPM2)3
Variable Torque Curve
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   
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Variable Torque Curve
Region of continuous
operation
Region of intermittent
operation
Torque
(Typical)
200%
100%
63%
Continuous torque
capability
Peak torque
capability
Requirement
60
Speed in Hertz
120
Variable Torque - Flow
Flow is proportional to speed.
(Flow1 / Flow2) = (RPM1) / (RPM2)
Flow
Gallons/min
10000
RPM
1800
Second
RPM
900
Second
Flow
5000.00
Variable Torque - Pressure
Pressure is proportional to the
square of the speed.
(Press1 / Press2) = (RPM1)2 / (RPM2)2
Pressure
Lb/sq. in
1000
RPM
1800
Second
RPM
3600
Second
Pressure (lb/sq. in)
4000
Variable Torque - HP
HP is proportional to the cube of the speed.
(HP1 / HP2) = (RPM1)3 / (RPM2)3
Horsepower RPM
10
1800
Second
RPM
3600
Second
Horsepower
80.00
Energy Savings Using VFD’s
Energy Savings Using VFD's
Motor
RPM
HP
Eff
PF
Amps
Volts
kW
Rate / Hr
24 Hrs
Annual Cost
VFD
1750
30.0
88%
90%
35.47
460
25.43
0.06
\$
36.62
\$ 13,366.96
RPM
HP
Eff
PF
Amps
Volts
kW
Rate / Hr
24 Hrs
\$
Annual Cost \$
1750
30.0
89%
97%
32.54
460
25.15
0.06
36.21 \$
13,217 \$
1600
1500
22.9
18.9
89%
89%
97%
97%
24.87
20.49
460
460
19.22
15.84
0.06
0.06
27.67 \$ 22.80 \$
10,101 \$ 8,323 \$
1400
15.4
89%
97%
16.66
460
12.87
0.06
18.54 \$
6,767 \$
Operating Costs
Hrs
% speed
RPM
HP
Eff
PF
Amps
Volts
kW
Rate / Hr
Total
\$
Annual Cost \$
3
60%
1050
6.48
89%
97%
7.03
460
16.29
0.06
0.98 \$
357 \$
6
1.5
100%
75%
1750
1312.5
30.00
12.66
89%
89%
97%
97%
32.54
13.73
460
460
150.88
15.91
0.06
0.06
9.05 \$
0.95 \$
3,304 \$
348 \$
9
80%
1400
15.36
89%
97%
16.66
460
115.87
0.06
6.95 \$
2,538 \$
1300
12.3
89%
97%
13.34
460
10.31
0.06
14.84 \$
5,418 \$
1200
9.7
89%
97%
10.49
460
8.11
0.06
11.68 \$
4,261 \$
900
4.1
89%
97%
4.43
460
3.42
0.06
4.93
1,798
Formulas
3
80%
1400
15.36
89%
97%
16.66
460
38.62
0.06
2.32 \$
846 \$
1.5
90%
1575
21.87
89%
97%
23.72
460
27.50
0.06
1.65
602
HP2 = HP1 x ( RPM2/RPM1)3
kW = (E x I x PF x 1.732) / 1000
Amps = (746 x HP) /(1.732 x E x Eff x PF)
Kw / Hr Rate
\$
0.06
Voltage
460
Totals
kW
Rate / Hr
24 Hrs
Annual Cost
365.08
0.06
\$
\$
21.90
7,995.00
Variable Torque Applications
• Irrigation Water Pumps
• Downhole Water Pumps
• Submersible Water
Pumps
• Domestic Water Pumps
• Centrifugal Sewage
Treatment Pumps
•
•
•
•
Centrifugal Fans
Blowers
Air Handling Units
Chillers
Types of Three Phase AC Motors
used on Pumps
Horizontal foot mounted
Close coupled
Belt driven
Gear reducer
Available in
NEMA MG1 Part 30
&
NEMA MG1 Part 31
Vertical
Hollow shaft
Solid shaft
Submersible
Specialized winding
process
Available in
NEMA MG1 Part 30
only
Single Phase Motors
IMPORTANT
NOTICE!!!!!
Single Phase Motor
Cannot be used with a VFD
Three Phase Motor
with THREE Phase Input
L1
L2
L3
T1
T2
T3
VFD is sized by the
of the motor.
Three Phase Motor
with SINGLE Phase Input
T1
L1
T2
T3
L2
Output Voltage is
the same as Input
Voltage.
VFD is sized by the
of the motor multiplied by 1.7
eg.
For a 10HP motor with a FLA of
12 amps.
The VFD size would be
12 x 1.7 = 20.4 amps
Pump Packaging Options
• Reactors line and load, Harmonic Filters, Sine Wave
DV/DT Filters
• Disconnect, fusible or non-fusible
• Bypass system, Cam Switch, 2 contactor,
3 contactor
• Serial communication HVAC protocols
• Standard and custom door mounted controls; any
combination
• Pre-engineered packages
– Nema 1, Nema 12, Sprinkler Proof and Nema 3R
• Custom engineered packages
Bypass Package Nema 3R
• Options
– Fusible disconnect
– 3 Contactor Bypass
– Line Reactor
– Forced Air Ventilation
Pump Packages
• Standard Enclosure Options:
– Nema 1
– Nema 12
– Nema 3R
– Sprinkler Proof
– Wall Mount
– Floor Mount
WELLMAX
•
•
•
•
•
A USER FRIENDLY GRAPHICAL TOUCH SCREEN LCD with
sensible wording for easy operation.
Displays historical data of TORQUE, AMPS, and RPM (standard).
You can zoom in & out to examine any data point of interest.
An optional memory card will CONSTANTLY STORE DATA, which can be retrieved by the
user.
An optional four inch printer will be available for on the site printing of information.
PUMPOFF CONTROL features will prolong the life of the pump by monitoring and
maintaining an approximate FLUID LEVEL.
SERIAL port available for COMMUNICATION. Optional interface available for
MODBUS protocols.
Option - A LOW COST SATELLITE COMMUNICATION link, which allows Internet
viewing of 10 points of information as well as voice call out ability on alarm situations for \$6
per day.
WELLMAX
CONTROLLER
PUMPOFF
CONTROLLER
Constant Torque Curve
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Constant Torque
• Torque remains constant up to
the motor base speed.
• HP is proportional to the speed.
Constant Torque Applications
•
•
•
•
•
•
Conveyors
Compressors
Positive Displacement Pumps
Crushers
Mixers
Etc.
Positive Displacement Pumps
R e g io n o f in te rm itte n t
o p e ra tio n
R e g io n o f c o n tin u o u s
o p e ra tio n
R e g io n o f in te rm itte n t
o p e ra tio n
T o rq u e
(T yp ic a l)
200%
100%
63%
P e a k to rq u e
c a p a b ility
C o n tin u o u s to rq u e
c a p a b ility
L o a d to rq u e
re q u ire m e n t
60
100
S p e e d in H e rtz
Region of intermittent
operation
Region of continuous
operation
Field weakening region
200%
Torque
(Typical)
Peak torque capability
provided that the AC
100%
Continuous torque
capability limited
by motor cooling
63%
requirement
60
Speed in Hertz
100
Torque Derating Due to
Motor Cooling
F ie ld w e a k e n in g r e g io n
(T y p ic a l)
T o rq u e
200%
P e a k to r q u e c a p a b ility
p r o v id e d th a t th e A C
d riv e h a s a d e q u a te
o v e r lo a d c a p a b ility
100%
C o n tin u o u s to r q u e
c a p a b ility lim ite d
b y m o to r c o o lin g
63%
60
S p e e d in H e r tz
100
Torque Curve Below & Above 60 Hz,
Constant Torque V/F Ratio
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
 
 
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  
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Application Considerations
•
•
•
•
•
•
•
Motor voltage, HP & FLA specifications
Load type, constant or variable torque
Control system requirements
Serial communication protocol
Analog and digital input and
outputs
Harmonic considerations
Nuisance tripping concerns
Motor insulation protection
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