Drive Solutions for the Global Oil and Gas Industry ... - GE Energy

Three-
Phase Electric
Electric Supply
Supply
Calculations for Mechanical Speed Control Systems
Calculations for Mechanical Speed Control Systems
If the energy cost is to be compared with a mechanical variable speed system, the previous calculation must be repeated.
There If the energy are three cost main is to mechanical be compared flow with control mechanical systems as variable described speed in system, the large the table previous of pages calculation 4 and 5: must be repeated.
There
•
are
A fixed
three
speed
main mechanical
motor and pump,
flow control
compressor,
systems
or
as
fan
described
with a flow
in the
throttling
large table
valve
of
or
pages
variable and
guide
5:
vanes.
• A fixed
fixed
speed
speed
motor
motor
and
and
hydraulic
pump, compressor,
variable speed
or fan
transmission
with flow throttling
driving a
valve
variable
or variable
speed pump
guide
or
vanes.
compressor.
• A variable
fixed speed
speed
motor
steam
and
or
hydraulic
gas turbine
variable
driving
speed
a variable
transmission
speed pump
driving
or compressor.
variable speed pump or compressor.
The methods variable for calculating speed steam these or costs gas turbine are outlined driving in the variable chart speed below. pump A load or profile compressor. similar to the previous page is
used. The methods Spreadsheets for calculating for calculating these costs the savings are outlined and payback in the chart for below. a fan are available load profile from similar the Web to the site previous www.tmge.com page is .
used. Spreadsheets for calculating the savings and payback for fan are available from the Web site www.tmge.com Fig. 1 Pump Performance Chart & Load Curve To calculate the energy used by a flow
Flow Throttling Valve Control
Fig. 1 Pump Performance Chart & Load Curve To throttling calculate system, the energy start with used the by desired a flow
Flow Throttling Valve Control
throttling output flow, system, say 90%. start Obtain with the the desired pump
Pump hp
output performance flow, say chart 90%. (head Obtain vs flow, the pump with pump
Pump 1,900 hp
performance horsepower). chart Find the (head horsepower vs flow, with required pump
1,900
C A
horsepower). when the pump Find is running the horsepower at the fixed required
Electric Motor
100
C A
when the pump is running at the fixed
Electric Motor
100
motor speed of 1,800 rpm and delivering
Threemotor
speed of 1,800 rpm and delivering
Three- Phase
Valve or
the reduced flow at C in Figure 1. Proceed
Phase Electric
Valve Damper or
the as in reduced the electrical flow at example, C in Figure working 1. Proceed back
Electric Supply
Damper Control
Valve as to the in the motor. electrical Calculate example, the shaft working kW used back
Supply
Control
Valve
Fixed speed Fixed speed
Open to and the the motor. electrical Calculate power the cost. shaft kW used
Fixed speed Fixed speed
Open and References the electrical below power give examples. cost.
References below give examples.
80 90 100
Repeat for the other flows in the load
80 Percent Output 90 Flow 100
Repeat profile, and for the total other energy flows in usage. the load
Percent Output Flow
profile, and total the energy usage.
Hydraulic Variable Speed Control
Hydraulic Variable Speed Control
Speed
Electric Motor
Three-
Speed
Electric Motor
N2
Hydraulic
Phase
N2
Efficiency % %
100
100
90
90
80
80
Fixed speed
Fixed speed
Var. Hydraulic Speed
Var. Control Speed
Control
70
70 60 70 *
*
60 70
Output 80 80 Speed 90 90
%
100
100
Output Speed %
Variable Speed Turbine Control
Variable Speed Turbine Control
Steam,
Steam, Gas, or
Gas, Kerosene or Fuel or
Kerosene Fuel Steamor
Control Steam
Control
Electric Drive
Electric Drive
Hydraulic Transmission
Hydraulic Transmission
Hydraulic Coupling
Hydraulic Coupling
Variable speed
Variable turbine speed
turbine
Speed
Speed N2
N2
Variable speed
Variable speed
Figure 2.
Figure Hydraulic 2.
Hydraulic Transmission
Transmission
Efficiency
Efficiency
Variable speed
Variable speed
Percent Pressure (Head)
Pump Curve
Pump Curve
1,800 rpm
1,800 rpm
Fig. 3 Pump Performance Chart & Load Curve
Fig. 3 Pump Performance Chart & Load Load Curve
Load Curve
Curve (Process)
A (Process)
100
A
100
Percent Pressure (Head)
Fig. 4 Pump Performance Chart & Load Curve
Fig. 4 Pump Performance Chart & Load Load Curve
Load Curve
Curve (Process)
A (Process)
100
A
100
Percent Pressure (Head)
Pump Curve
Pump Curve
1,800 rpm
1,800 rpm
Speed N2
Speed N2
80 90 100
80Percent Output 90 Flow 100
Percent Output Flow
Pump Curve
Pump Curve
1,800 rpm
1,800 rpm
Speed N2
Speed N2
B
B1,500 hp
1,500 hp
B
B1,500 hp
1,500 hp
80 90 100
80Percent Output 90 Flow 100
Percent Output Flow
To calculate the energy used by a variable
To speed calculate hydraulic the transmission energy used by system, a variable start
speed with the hydraulic desired pump transmission output flow. system, Using start
with the pump the desired chart, find pump the output horsepower flow. Using
the required pump when chart, the find pump the horsepower is running at the
required reduced speed when the N2 pump and delivering is running the at the
reduced speed flow at N2 B in and Figure delivering 3. Obtain the the
reduced transmissiom flow at efficiency B in Figure from 3. the Obtain the
transmissiom manufacturer (Figure efficiency 2). from Note the the low
manufacturer efficiency at reduced (Figure speeds. 2). Note Proceed the low as
efficiency in the electrical at reduced example, speeds. working Proceed back as to
in the the motor electrical and calculating example, working the energy back cost. to
the Reference motor and 1 gives calculating examples. the energy cost.
Reference 1 gives examples.
Repeat for the other flows in the profile
Repeat and total for the the energy other usage. flows in the profile
and total the energy usage.
To calculate the energy used by a
To variable calculate speed the turbine energy system, used by take a the
variable pump chart speed and turbine load curve. system, Find take the the
pump horsepower chart and required load when curve. the Find pump the is
horsepower running at the required reduced when speed the N2 pump andis
running delivering at the reduced flow speed at B N2 inand
delivering Figure 4. Find the reduced the turbine flow fuel at B or insteam
Figure consumption 4. Find at the this turbine speed fuel andor steam
consumption horsepower, and at this calculate speed the andcost for the
horsepower, number of running and calculate hours. the cost for the
number of running hours.
Repeat for the other flows in the profile
Repeat and total for the the energy other usage. flows in the profile
and total the energy usage.
A number of free publications on this topic are available from the library at www.tmge.com , including the following:
number of free publications on this topic are available from the library at www.tmge.com , including the following:
1. Selecting Variable Speed Drives for Flow Control, brochure GEA-13873 - discusses the various mechanical speed
1. control Selecting systems Variable and Speed outlines Drives the calculation for Flow Control, of energy brochure savings, GEA-13873 in particular discusses for hydraulic the various transmission mechanical speed speed control.
2. control Adjustable systems Frequency and outlines Drives the for Pump calculation Energy of energy Savings savings, Power in Generating particular for Stations hydraulic - discusses transmission pump speed energy control.
2. calculations.
Adjustable Frequency Drives for Pump Energy Savings in Power Generating Stations discusses pump energy
3. AC calculations. Adjustable Speed Drive Systems for Cement Kiln Induced Draft Fans - discusses large fan energy calculations.
3. AC Adjustable Speed Drive Systems for Cement Kiln Induced Draft Fans discusses large fan energy calculations.
Revised: 5-22-09 © 2009 TMEIC GE Automation Systems. All Rights Reserved.
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