variable frequency drive corner arm pivot case study · 1) centrifugal pump and level terrain, 2)...

Initiated by Alberta Agriculture and Rural Development, funding for this Canada-Alberta cost-shared project was provided by Agriculture and Agri-Food Canada though the Agricultural Flexibility Fund, as part of Canada’s Economic Action Plan.

Variable frequency drive corner arm centre pivot system pump case study

Part 2: Data collection and results

Prepared by: Gregg Dill, P.Eng.

October 2012

VFD

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Variable frequency drive corner arm

centre pivot system pump case study



October 2012

SUMMARY

A corner arm centre pivot operates about 20% of a circle at the maximum flow rate and 80% of

the circle at flow rates lower than the maximum flow rate. A typical flow rate range is 700 to

1200 gpm for a quarter section system irrigating approximately 155 acres. A corner arm centre pivot

pumping unit is designed to deliver the maximum flow rate at the maximum pressure and, therefore,

operates at lower flow rates and higher than required pressures for most of the circle. The variable

frequency drive (VFD) adjusts the motor speed to allow the pump to deliver the required flow rate at

the required pressure which, effectively, reduces the kilowatts of power required for most of the circle.

The energy consumption of a pumping unit, controlled with No VFD and with a VFD, for a corner

arm centre pivot irrigation system was measured to identify potential energy savings. Each system was

operated with a VFD controlled by a pressure sensor at the pump discharge, with a VFD controlled by

a pressure sensor at the corner arm tower, and with No VFD. Four systems were monitored;

1) centrifugal pump and level terrain, 2) centrifugal pump and rolling terrain, 3) turbine pump and

level terrain, and 4) turbine pump and rolling terrain. A trailer-mounted VFD was moved to each site

and connected to the power panel of the pump for each of the four existing corner arm centre pivot

irrigation systems.

The price of electricity used to determine savings was $0.16 per kWh ($0.08 per kWh plus line

provider Transmission and Distribution components and riders). Annual energy use and costs were

based on pumping 12 inches (300 mm) of water during the irrigation season. The payback period was

calculated by dividing the additional cost of installing a VFD controlled at the pump discharge

($7,000) by the annual savings. The VFD cost increased by $3,500 to $10,500 for installing wireless

radios to transmit the corner tower pressure to the pump site. Annual savings and the payback period

would vary based on terrain and other site specific factors.

The energy and dollar savings for operating a corner arm centre pivot system pump with a VFD

controlled with a pressure sensor at the corner arm tower were higher than when operating with a

pressure sensor at the pump.

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There were 29.7 and 33.2 % reductions in energy used to irrigate on level terrain using a VFD

controlled by the pressure at the corner tower compared to the pumping unit operated with No VFD.

The cost of a VFD to control the pumping unit on level terrain using the pressure at the corner tower

was recovered in 4.8 and 4.5 years. In comparison, the energy savings were 28.1 and 41.8 % for

rolling terrain and the payback periods were 7.3 and 3.6 years.


controlled by the pressure at the pump discharge compared to the pumping unit operated with No

VFD. The cost of a VFD to control a pumping unit on level terrain using the pressure at the pump

discharge was recovered in 20.8 and 3.9 years. In comparison, the energy savings were 4.7 % for both

sites on rolling terrain and the payback periods were 21.4 and 28.9 years.

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Variable frequency drive corner arm

centre pivot system pump case study



October 2012

PROJECT DESCRIPTION

General

A corner arm centre pivot operates about 20% of a circle at the maximum flow rate and 80% of the

circle at flow rates lower than the maximum flow rate. A typical flow rate range is 700 to 1200 gpm

for a quarter section system irrigating approximately 155 acres. A corner arm centre pivot pumping

unit is designed to deliver the maximum flow rate at the maximum pressure and, therefore, when it

operates at lower flow rates the pressure is higher than required for most of the circle. The variable

frequency drive (VFD) adjusts the motor speed to allow the pump to deliver the required flow rate at

the required pressure which, effectively, reduces the kilowatts of power required for most of the circle.

The energy consumption of a pumping unit, controlled with No VFD and with a VFD, for a corner

arm centre pivot irrigation system was measured to identify potential energy savings. The feasibility

of using a VFD to control a pump on a corner arm centre pivot was investigated (1) and based on the

analysis, four pump-terrain combinations were identified for this case study. Four systems were

monitored; 1) centrifugal pump and level terrain, 2) centrifugal pump and rolling terrain, 3) turbine

pump and level terrain, and 4) turbine pump and rolling terrain. Each system was operated with a VFD

controlled by a pressure sensor at the pump discharge, with a VFD controlled by a pressure sensor at

the corner arm tower, and without a VFD. A trailer-mounted VFD was moved to each site and

connected to the power panel of the pump for each of the four existing corner arm centre pivot

irrigation systems. The pressure sensor mounted at the end of the corner arm required a wireless

system to send the pressure signal to the VFD located at the edge of the field, which added about

$3,500 to the cost of the VFD corner arm control option.

Variable frequency drive

Rivers Electric (Taber) Co. Ltd. supplied the magnetic starter and a variable torque control VFD

(Cutler-Hammer SVX9000) and installed both units in a trailer that was moved to each site. At each

site the power cable supplying power to the pump was disconnected from the electrical panel and

connected to the magnetic starter (mag) and VFD in the trailer.

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Instrumentation

Instrumentation included an ultrasonic flow meter or a propeller flow meter, two wired pressure

sensors, three wireless pressure sensors, a power meter on the irrigation system service supply, a power

meter on the input to the VFD, a wireless GPS receiver on the last tower of the centre pivot, a wireless

GPS receiver on the corner arm tower, and a speed monitor on the pump/motor. Information on sensor

and instrumentation manufacturers, model numbers and suppliers is provided in Appendix A of the

Part 1 report (2). Brochures and more detailed technical information about the sensors and

instrumentation are included in Appendix D of the Part 1 report (2).

The instrumentation and data collection developed and assembled for the 2010 Irrigation system

energy trial assessment project (3) was used as the basis for this project. All data, including data from

the two power meters, was collected and stored on one data logger. GPS data and pump speed was

also collected by the same data logger eliminating the need to try and synchronize data from different

data loggers to the same time. The data logger was located in a cube van at the edge of the field near

the electrical power panel.

Data logger

A Campbell Scientific Inc. (CSI) CR1000 data logger was used to collect and pre-process the data.

Data was recorded on a one minute interval for a complete circle. The data signals from the power

meters were converted from RS485 to RS232 and connected to COM (communication) ports on the

data logger. The RS232 signals from the two GPS receivers were also connected to COM ports on the

data logger. A customized program was developed to collect and record the data from the

instrumentation and sensors. Power and communication requirements for each instrument and sensor

are discussed in Part 1 of this report.

Flow meter

A GE Panametrics PT878 ultrasonic flow meter was used to record system water flow rate data. A

4-20 ma output cable, supplied by GE Panametrics (p/n 704-609), was required to transfer the

instantaneous flow rate data to the data logger.

A McCrometer M0308 McPropeller flow meter with McCrometer McSpaceSaver FS100 flow

straightener vanes was used on one system that did not have the required pipe length before and after

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the ultrasonic flow meter to ensure the required accuracy. A McCrometer EA631 pulse transmitter

was required to transmit the signal to the data logger.

Power meters

Two Acuvim II power meters were used to monitor power quality parameters. The power meters

were mounted in the VFD trailer. One power meter measured the irrigation system service supply and

the other power meter measured the input to the VFD. Data recorded included volts, amps, kilowatts

(kW) and power factor for each leg of the 3-phases and kilowatt hours (kWh), kilovolt-amp hours

(kVAh), kW demand and kilovolt-amp (kVA) demand for each test circle.

Pressure sensors

Pressure sensors were located on the intake and discharge of the centrifugal pumps and on the

discharge of the turbine pumps. The distance from the water level to the pump discharge was

measured for the turbine pumps. Wireless pressure sensors were located at the pivot point, end tower

and corner arm tower and the data was transmitted to the data logger. A 24 VDC power supply was

required for each pressure sensor and radio. The VFD was controlled by the pump discharge pressure

sensor for one circle and by the corner-arm pressure sensor for one circle.

GPS

John Deere Starfire iTC GPS receivers were used to identify the location of the end of the pivot and

the corner-arm to be used in determining the effect of elevation on the head required at the pump. The

data was also used to identify the location of the pivot in the 360 degree pivot rotation. The receivers

were activated for real time kinematic (RTK) accuracy. A 24 VDC power supply was required for

each GPS unit.

Speed sensor

The speed sensor was an optical sensor that was connected directly to the data logger P1 pulse

channel.

Wireless radios

Phoenix Contact 900 MHz radios were used to transfer the signal wirelessly from the pressure

sensors on the centre pivot and the GPS receivers at the pivot end and corner-arm towers to the data

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logger located at the pump site. This ensured the pivot pressure and location data were recorded at the

same time as the power, pump pressure, pump speed and flow data.

FIELD PROCEDURE

The VFD trailer was positioned beside the electrical service at each site. The pump power cable

was removed from the electrical service and connected to the mag/VFD in the trailer. The mag/VFD

was then connected to the electrical service. The instrumentation van was positioned beside the VFD

trailer and signal wires were connected to supply the pump discharge and corner pressure signal to

control the VFD and to provide the frequency signal from the VFD and the power meter data to the

datalogger. Power was supplied to the instrumentation van from the VFD trailer. The wired sensors

and measuring instruments were installed and connected to the data logger. The GPS receivers were

mounted at the end tower and corner tower. Pressure sensors were installed on couplers at the pivot

point, end tower and corner tower. Twenty four volt DC power was supplied from 480VAC to 24VDC

power transformers (provided by Rivers Electric) connected to the pivot power to provide power to the

GPS receivers, pressure sensors and radios.

Data was collected at each site from three circles at the application rate and timing specified by the

cooperator. A three position switch was used to change from mag (No VFD) to VFD operation

without requiring stopping irrigation to make the change. Rivers Electric also supplied a Siemens

programmable logic controller (PLC) to convert the pressure signals from 4-20 mA to 0-5 volts

required to control the VFD and as input to the datalogger. Control was changed from pump discharge

to corner control from a panel on the front of the PLC. The control pressure for the VFD was changed

directly on the VFD panel when control was changed for the corner control circle to the pump

discharge control circle. The control pressure for the corner tower control circle was determined from

the centre pivot sprinkler chart provided by the dealer when the pivot was purchased. The corner

control pressure was set using this information and the corner control circle was completed. The pump

discharge pressure required to provide the design corner tower pressure was identified from the corner

tower control circle data and used to set the pump discharge control pressure for the pump discharge

control circle. Data was downloaded after each circle was completed and preliminary analysis done.

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RESULTS and DISCUSSION

General

The price of electricity used to determine savings was $0.16 per kWh ($0.08 per kWh plus line

provider Transmission and Distribution components and riders, excluding demand and administration

charges). Annual energy use and costs were based on pumping 12 inches (300 mm) of water during

the irrigation season. Each site was adjusted based on the application rate during the testing. Although

the application rate varied from site to site, the application rate at each site was the same for all three

circles. The payback period was calculated by dividing the additional cost of installing a VFD

controlled at the pump discharge ($7,000) by the annual savings. The VFD cost increased by $3,500 to

$10,500 for installing wireless radios to transmit the corner tower pressure to the pump site. Annual

savings and the payback period would vary based on terrain and other site specific factors.

Charts of the data recorded for energy use, power, corner arm pressure, pump pressure, flow rate,

and elevation difference are in Appendices A to D for sites 1 to 4. The starting location (degrees) of

the centre pivot in the field varied from site to site and from circle to circle at each site. The data was

reorganized so each chart displayed results beginning at zero degrees which represents north at each

site. Charts of the elevation of the corner tower for each site are in Appendix E.

The results were not conclusive when comparing the turbine and centrifugal pumps because of

pump performance issues with Sites 1 and 4. The centrifugal pump at Site 1 developed higher pressure

than the design pressure with No VFD resulting in higher savings than expected when the pump was

controlled with the VFD. The centrifugal pump at Site 4 did not develop the required pressure with No

VFD and this resulted in lower savings than expected when the pump was controlled with the VFD.

Although the installation of a VFD saved energy at all sites; the pumping unit should be inspected

and maintenance performed prior to the installation of a VFD to realize maximum savings.

Level terrain

Energy savings were higher for a pump controlled by a pressure sensor at the corner tower (29.7

and 33.2 %) than the savings for a pump controlled by a pressure sensor at the pump discharge (4.6

and 25.6 %) on level terrain (Table 1). The centrifugal pump (Site 1) developed a higher pressure than

required when operated with No VFD which resulted in higher savings of 11,360 kWh or $1,818 than

the turbine pump (Site 2) operated with No VFD of 2,100 kWh or $336 when the VFD was controlled

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by the pump discharge pressure. Based on the cost of a VFD controlled by the pressure at the pump

discharge ($7,000) the payback period was 20.8 years for the turbine pump and 3.9 years for the

centrifugal pump.

Energy savings were similar for turbine and centrifugal pumps controlled by the pressure at the

corner tower. Savings were 13,660 kWh or $2,186 for the turbine pump operated when the VFD was

controlled by the corner tower pressure and 14,720 kWh or $2,355 for the centrifugal pump. Based on

the cost of a VFD controlled by the pressure at the corner tower, including the wireless pressure sensor

($10,500) the payback period was 4.8 years for the turbine pump and 4.5 years for the centrifugal

pump.

Level terrain Control sensor at pump discharge Control sensor on corner-arm

Turbine Centrifugal Turbine Centrifugal

No VFD VFD No VFD VFD No VFD VFD No VFD VFD

kWh/year 46,000 43,900 44,320 32,960 46,000 32,340 44,320 29,600

Cost ($/yr) $7,360 $7,024 $7,091 $5,274 $7,360 $5,174 $7,091 $4,736

Saving (kWh) 2,100 11,360 13,660 14,720

Saving ($) $336 $1,818 $2,186 $2,355

Saving (%) 4.6 25.6 29.7 33.2

Payback (years) 20.8 3.9 4.8 4.5

Table 1. Energy and cost savings for turbine and centrifugal pumps operated with No VFD and with a

VFD controlled by the pressure at the pump discharge and by the pressure at the pivot corner tower on

level terrain.

Rolling terrain

Energy savings were higher for a pump controlled by a pressure sensor at the corner tower than the

savings for a pump controlled by a pressure sensor at the pump discharge on rolling terrain (Table 2).

The centrifugal pump did not develop the pressure required to irrigate about 13 % of the circle when

operated with No VFD which resulted in lower savings of1,512 kWh or $242 than the turbine pump of

2,040 kWh or $326 when the VFD was controlled by the pump discharge pressure. Based on the cost

of a VFD controlled by the pressure at the pump discharge ($7,000) the payback period was 21.4 years

for the turbine pump and 28.9 years for the centrifugal pump.

Energy savings were higher for the turbine pump (Site 3) than the centrifugal pump (Site 4)

controlled by the pressure at the corner tower. Savings were 18,072 kWh or $2,892 for the turbine

pump operated when the VFD was controlled by the corner tower pressure and 8,980 kWh or $1,437

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for the centrifugal pump. As stated above, the savings for the centrifugal pump would be higher if the

pump had developed the pressure to irrigate the circle at the required pressure with No VFD. Based on

the cost of a VFD controlled by the pressure at the corner tower, including the wireless pressure sensor

($10,500) the payback period was 3.6 years for the turbine pump and 7.3 years for the centrifugal

pump.

Rolling terrain Control sensor at pump discharge Control sensor on corner-arm

Turbine Centrifugal Turbine Centrifugal

No VFD VFD No VFD VFD No VFD VFD No VFD VFD

kWh/year 43,200 41,160 31,996 30,484 43,200 25,128 31,996 23,016

Cost ($/yr) $6,912 $6,586 $5,119 $4,877 $6,912 $4,020 $5,119 $3,683

Saving (kWh) 2,040 1,512 18,072 8,980

Saving ($) $326 $242 $2,892 $1,437

Saving (%) 4.7 4.7 41.8 28.1

Payback (years) 21.4 28.9 3.6 7.3

Table 2. Energy and cost savings for turbine and centrifugal pumps operated with No VFD and with a

VFD controlled by the pressure at the pump discharge and by the pressure at the pivot corner tower on

rolling terrain.

Site 1 (Woordman Farms)

This was a level terrain site with a centrifugal pump and an elevation change of 10.2 feet (3.1 m)

and the pump site in the southeast corner. The water level was 8 feet (2.44 m) below the eye of the

impeller. The ground level at the pivot centre was 0.6 feet (0.17 m) lower than the eye of the impeller.

Water supply dugout

Pivot flow 1150 gpm @ 46 psi

Pump Paco 50157, 13.2 inch impeller

Motor Baldor 60 hp, 90.2 % efficiency

The application rate was 0.75 inches (19 mm). The pivot was equipped with 10 psi pressure

regulators that require a pressure of 15 psi to operate. The corner pressure was set to 25 psi to activate

the solenoid valves on the corner arm sprinklers. These solenoid valves should operate with a line

pressure of 15 psi. When this issue is resolved, the corner tower pressure would be reduced to 15 psi

which would result in additional energy savings. The pump at this site developed a higher pressure

than required when operated with No VFD. This resulted in higher savings when the pump was

operated with a VFD controlled by the pump discharge pressure than the other sites. The corner tower

pressure (Chart A.3) dropped below the required 25 psi when the pump discharge pressure was set at

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50 psi. A pump discharge pressure of 60 psi required to maintain the corner tower pressure at or above

the required 25 psi would result in lower savings from the VFD with pump discharge control compared

to the No VFD control.

The corner control pressure was 20 psi at the beginning of the test (Chart A.3) until it was realized

that a pressure of 25 psi was required to operate the corner arm solenoid valves. Flow for the No VFD

circle fluctuated and is not included in Chart A.5. Although the data fluctuated, the general trend of

the flow was consistent with the VFD circle data.

Site 2 (Prairieview Seed Potatoes)

This was a level terrain site with a turbine pump and an elevation change of 17 feet (5.2 m) and the

pump site in the northwest corner. The water level was 4.1 feet (1.24 m) below the centre of the pump

discharge pipe centre. The ground level at the pivot centre was 11.5 feet (3.5 m) lower than the pump

discharge pipe.

Water supply canal intake to pumping sump


Pump Flowserve 12SKH-3, 8 inch impeller

Motor US Motors 60 hp, 93.6 % efficiency

The application rate was 0.6 inches (15.2 mm). The pivot was equipped with 15 psi regulators that

require a pressure of 20 psi to operate. The corner pressure was set to 25 psi to activate the solenoid

valves on the corner arm sprinklers. These solenoid valves should operate with a line pressure of

15 psi. When this issue is resolved, the corner tower pressure could be reduced to 15 psi which would

result in additional energy savings.

The pump pressure sensor failed near the end of the No VFD circle (Chart B.4)

Site 3 (G. Thompson Livestock Co. Inc.)

This was a rolling terrain site with a turbine pump and an elevation change of 52.2 feet (15.9 m) and

the pump site in the southeast corner. The water level was 4.3 feet (1.3 m) below the centre of the

pump discharge pipe. The ground level at the pivot centre was 34.1 feet (10.4 m) lower than the pump

discharge pipe.

Water supply canal intake to pumping sump

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Pump Flowserve 12KS-3, 8.13 inch impeller



require a pressure of 25 psi to operate. The corner pressure was set to 25 psi.

The flow in the northwest corner increased for more degrees of rotation during the VFD pump

discharge control circle (Chart C.5) than the other circles and remained high until the same location in

the circle as the other circles. The effect of the increased flow is consistent in the pressure and energy

data.

Site 4 (Grow The Energy Circle Ltd.)

This was a rolling terrain site with a centrifugal pump and an elevation change of 49.2 feet (15.0 m)

and the pump site near the middle of the east side. Although, this was a pressure pipeline, the pump

required priming and the intake pressure was negative during the tests. The ground level at the pivot

centre was 7.7 feet (2.36 m) lower than the pump discharge pipe.

Water supply pressure pipeline - required priming to start


Pump Cornell 5RB, 12.19 inch impeller



require a pressure of 20 psi to operate. The corner pressure was set to 20 psi. In No VFD operation

mode, the pump did not develop the pressure required to irrigate about 13 % of the circle at an

elevation of ~30 feet (~9 m) above the pumping unit. To irrigate this part of the field would require

the pumping unit to develop an additional 11 to 16 psi. If the pumping unit had developed the required

pressure in No VFD operation, the savings when operated in VFD control would be higher.

Due to a low area in the northwest corner of the field the application was reduced from 0.37 inches

(9.4 mm) to 0.2 inches (5.1 mm) over the contributing area. The crop was being germinated and

required the application be reduced to ensure germination by increasing the timer setting from 54 % to

100 %. The effect of the higher rotation speed can be seen in the energy use (Chart D.1). The energy

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use was adjusted by using the 54 % the pivot was operating for the majority of the circle to create a

ratio of 1:1.85 for the part of the circle operated at 100 %.

CONCLUSIONS

There were 29.7 and 33.2 % reductions in energy used to irrigate a quarter section corner arm centre

pivot on level terrain using a VFD controlled by the pressure at the corner tower compared to the

pumping unit operated with No VFD. The cost of a VFD to control the pumping unit on level terrain

using the pressure at the corner tower was recovered in 4.8 and 4.5 years when the payback period was

calculated by dividing the cost by the annual savings with an energy price of $0.16 per kWh. In

comparison, the energy savings were 28.1 and 41.8 % for rolling terrain and the payback periods were

7.3 and 3.6 years.

The energy and dollar savings for operating a corner arm centre pivot system pump with a VFD

controlled with a pressure sensor at the corner arm tower were higher than when operating with a

pressure sensor at the pump.


controlled by the pressure at the pump discharge compared to the pumping unit operated with No

VFD. The cost of a VFD to control a pumping unit on level terrain using the pressure at the pump

discharge was recovered in 20.8 and 3.9 years. In comparison, the energy savings were 4.7 % for both

sites on rolling terrain and the payback periods were 21.4 and 28.9 years.

The results were not conclusive when comparing the turbine and centrifugal pumps because of

pump performance issues with Sites 1 and 4. The centrifugal pump at Site 1 developed higher pressure

than the design pressure with No VFD resulting in higher savings than expected when the pump was

controlled with the VFD. The centrifugal pump at Site 4 did not develop the required pressure with No

VFD and this resulted in lower savings than expected when the pump was controlled with the VFD.

ACKNOWLEDGEMENTS

Partner

Rivers Electric (Taber) Co. Ltd.

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Cooperators

Woordman Farms Prairieview Seed Potatoes G. Thompson Livestock Co. Inc. Grow the Energy Circle Ltd.

Other

Oliver Irrigation RPH Irrigation Services Ltd. New Way Irrigation Alberta Agriculture and Rural Development, AgTech Centre Funding

Initiated by Alberta Agriculture and Rural Development, funding for this Canada-Alberta cost-

shared project was provided by Agriculture and Agri-Food Canada though the Agricultural

Flexibility Fund, as part of Canada’s Economic Action Plan.

Disclaimers

This document was prepared exclusively as information for Alberta Agriculture and Rural

Development. The views and opinions expressed in this report are those of Gregg Dill and not

necessarily those of Agriculture and Agri-Food Canada, or Alberta Agriculture and Rural

Development.

REFERENCES

1.Gregg Dill. Feasibility of using a VFD controlled pump on a corner arm pivot irrigation

system. 2011. Alberta Agriculture and Rural Development, Agtech Centre, Lethbridge, AB. 17

pp.

2. Gregg Dill. Variable Frequency Drive Corner Arm Pivot Case Study Part 1: Instrumentation and

data collection equipment. 2011. Alberta Agriculture and Rural Development, Agtech Centre,

Lethbridge, AB. 75 pp.

3. Gregg Dill. Irrigation System Energy Trial Assessment Project. 2010. Alberta Agriculture and

Rural Development, Agtech Centre, Lethbridge, AB.

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APPENDIX A

Graphs of data recorded for Site 1

0

500

1000

1500

2000

2500

3000

0 45 90 135 180 225 270 315 360

Ene

rgy

use

(kil

ow

att-

ho

urs

)

Degrees

Corner control Discharge control No VFD

Chart A.1. Accumulated kilowatt hours of electricity used to apply 0.75 inch (19 mm) of water

operated with No VFD, with a VFD controlled by the corner tower pressure, with a VFD controlled by

the pump discharge pressure.

0

10

20

30

40

50

60

0 45 90 135 180 225 270 315 360

Po

we

r (k

ilo

wat

ts)

Degrees


Chart A.2. Kilowatts of energy required for the pumping unit for each control method.

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0

10

20

30

40

50

60

70

0 45 90 135 180 225 270 315 360

Pre

ssu

re (

psi

)

Degrees


Chart A.3. Corner tower pressure recorded for each control method.

0

10

20

30

40

50

60

70

80

0 45 90 135 180 225 270 315 360

Pre

ssu

re (

psi

)

Degrees


Chart A.4. Pump discharge pressure recorded for each control method.

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0

200

400

600

800

1000

1200

1400

0 45 90 135 180 225 270 315 360

Flo

w (g

pm

)

Degrees

Corner control Discharge control

Chart A.5. Flow rate recorded for two of the control methods.

-1

0

1

2

3

4

0 45 90 135 180 225 270 315 360

Ele

vati

on

dif

fere

nce

(m

etr

es)

Degrees

Pump to pivot end tower Pump to corner tower

Pump elevation = 0

Pivot point elevation

Chart A.6. Elevation change from the pump to the end tower and corner arm tower.

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APPENDIX B


0

500

1000

1500

2000

2500

0 45 90 135 180 225 270 315 360

Ene

rgy

use

(kil

ow

att-

ho

urs

)

Degrees


Chart B.1. Accumulated kilowatt hours of electricity used to apply 0.6 inch (15.2 mm) of water

operated with No VFD, with a VFD controlled by the corner tower pressure, with a VFD controlled by

the pump discharge pressure.

0

10

20

30

40

50

60

0 45 90 135 180 225 270 315 360

Po

we

r (k

ilo

wat

ts)

Degrees


Chart B.2. Kilowatts of energy required for the pumping unit for each control method.

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0

10

20

30

40

50

60

70

0 45 90 135 180 225 270 315 360

Pre

ssu

re (

psi

)

Degrees


Chart B.3. Corner tower pressure recorded for each control method.

0

20

40

60

80

100

120

0 45 90 135 180 225 270 315 360

Pre

ssu

re (

psi

)

Degrees


Chart B.4. Pump discharge pressure recorded for each control method.

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0

200

400

600

800

1000

1200

1400

0 45 90 135 180 225 270 315 360

Flo

w (g

pm

)

Degrees


Chart B.5. Flow rate recorded for each control method.

-2

-1

0

1

2

3

4

5

0 45 90 135 180 225 270 315 360

Ele

vati

on

dif

fere

nce

(m

etr

es)

Degrees



Pump elevation = 0

Chart B.6. Elevation change from the pump to the end tower and corner arm tower.

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APPENDIX C


0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 45 90 135 180 225 270 315 360

Ene

rgy

use

(kil

ow

att-

ho

urs

)

Degrees


Chart C.1. Accumulated kilowatt hours of electricity used to apply 0.5 inch (12.5 mm) of water

operated with No VFD, with a VFD controlled by the corner tower pressure and with a VFD

controlled by the pump discharge pressure.

0

10

20

30

40

50

60

0 45 90 135 180 225 270 315 360

Po

we

r (k

ilo

wat

ts)

Degrees


Chart C.2. Kilowatts of energy required for the pumping unit for each control method.

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0

10

20

30

40

50

60

70

80

90

0 45 90 135 180 225 270 315 360

Pre

ssu

re (

psi

)

Degrees


Chart C.3. Corner tower pressure recorded for each control method.

0

10

20

30

40

50

60

70

80

90

0 45 90 135 180 225 270 315 360

Pre

ssu

re (

psi

)

Degrees


Chart C.4. Pump discharge pressure recorded for each control method.

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0

200

400

600

800

1000

1200

1400

0 45 90 135 180 225 270 315 360

Flo

w (g

pm

)

Degrees


Chart C.5. Flow rate recorded for each control method.

-14

-12

-10

-8

-6

-4

-2

0

2

4

6

0 45 90 135 180 225 270 315 360

Ele

vati

on

dif

fere

nce

(m

etr

es)

Degrees


Pump elevation = 0


Chart C.6. Elevation change from the pump to the end tower and corner arm tower.

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APPENDIX D


0

100

200

300

400

500

600

700

800

900

0 45 90 135 180 225 270 315 360

Ene

rgy

use

(kil

ow

att-

ho

urs

)

Degrees


Chart D.1. Accumulated kilowatt hours of electricity used to apply 0.37 inch (9.4 mm) of water

operated with No VFD, with a VFD controlled by the corner tower pressure and with a VFD controlled

by the pump discharge pressure.

0

5

10

15

20

25

30

35

40

45

0 45 90 135 180 225 270 315 360

Po

we

r (k

ilo

wat

ts)

Degrees


Chart D.2. Kilowatts of energy required for the pumping unit for each control method.

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0

10

20

30

40

50

60

0 45 90 135 180 225 270 315 360

Pre

ssu

re (

psi

)

Degrees


Chart D.3. Corner tower pressure recorded for each control method.

0

10

20

30

40

50

60

70

0 45 90 135 180 225 270 315 360

Pre

ssu

re (

psi

)

Degrees


Chart D.4. Pump discharge pressure recorded for each control method.

of 29

0

200

400

600

800

1000

1200

1400

0 45 90 135 180 225 270 315 360

Flo

w (g

pm

)

Degrees


Chart D.5. Flow rate recorded for each control method.

-8

-6

-4

-2

0

2

4

6

8

10

12

0 45 90 135 180 225 270 315 360

Ele

vati

on

dif

fere

nce

(m

ete

rs)

Degrees


Pump elevation = 0


Chart D.6. Elevation change from the pump to the end tower and corner arm tower.

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Appendix E

Field elevations

780

800

820

840

860

0 45 90 135 180 225 270 315 360

Ele

vati

on

(me

tre

s)

Degrees

Site 1 Site 2 Site 3 Site 4

Chart E.1. Elevation of the corner tower over one rotation for each site.

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APPENDIX F

Glossary

acre one acre comprises 4,840 square yards or 43,560 square feet. Originally, an acre was understood as an

area of land sized at one furlong (660 ft) long and one chain (66 ft) wide. This may have also been

understood as an approximation of the amount of land an ox could plough in one day. As a unit of

measure an acre has no prescribed shape so any perimeter enclosing 43,560 square feet is an acre in

size. Source Wikipedia

centre-pivot irrigation machine (centre-pivot and moving lateral irrigation machines)

automated irrigation machine consisting of a number of self-propelled towers supporting a pipeline

rotating around a pivot point and through which water supplied at the pivot point flows radially

outward for distribution by sprayers or sprinklers located along the pipeline Source ISO

centrifugal pump pump with an impeller along or near to the rotating axis that is accelerated by an impeller, flowing

radially outward or axially into a diffuser or volute chamber, from where it exits into the downstream

piping system Source Wikipedia (adapted)

corner arm centre pivot irrigation system centre-pivot irrigation machine with a pipeline connected to the end and supported by a steerable

tower. The pipeline swings outward into the corners and allows irrigation of most of the area in the

corners. No source

effective radius (centre-pivot and moving lateral irrigation machines)

radius of the circular-field are to be irrigated by a centre-pivot irrigation machine, measured as the

distance from the pivot point to the terminal sprayer or sprinkler on the pipeline Source ISO

endgun (centre-pivot and moving lateral irrigation machines)

set of one or more sprinklers installed on the distal end(s) of a centre-pivot or moving lateral irrigation

machine to increase the irrigated area Source ISO

global positioning system (GPS) a space-based satellite navigation system that provides location and time information in all weather,

anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS

satellites. It is maintained by the United States government and is freely accessible to anyone with a

GPS receiver. Source Wikipedia

irrigation system (irrigation control head)

assembly of pipe, components, and devices installed in the field for the purpose of irrigating a specific

area Source ISO

low pressure operation pressure between 15 and 25 psi (100 and 170 kPa) No source

one acre-inch the volume of water required to cover an acre one inch deep. Equals 3,630 cubic feet, 27,154 US

gallons or 102,790 litres. Source http://www.diracdelta.co.uk or http://dictionary.reference.com

http://www.diracdelta.co.uk/http://dictionary.reference.com/

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sprinkler (sprinklers)

water distribution device of a variety of sizes and types, for example, impact sprinkler, fixed nozzle,

sprayer, irrigation gun Source ISO

turbine pump pump consisting of one or more impellers in series at the end of a shaft that is submerged in water and

connected to a power unit above water level No source

variable-frequency drive (VFD) (also adjustable-frequency drive, variable-speed drive, AC drive, micro drive or inverter drive)

a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed

and torque by varying motor input frequency and voltage Source Wikipedia

variable frequency drive corner arm pivot case study · 1) centrifugal pump and level terrain, 2)...

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