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Title: Note- Variables Speed Drives
Description: Interesting note on variable speed drives
Description: Interesting note on variable speed drives
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ABB drives
Technical guide No
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4
Technical guide No
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All rights reserved
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3AFE61389211 REV C 12
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2011
Technical guide No
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4
Contents
Chapter 1 - Introduction
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7
Chapter 2 - Processes and their requirements
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8
Industrial segments with VSD processes
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10
Machines are used to alter materials’ properties
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11
Indefinite shape
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and to transport materials
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12
Liquid materials
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12
Chapter 3 - The workhorse of industry: the electric motor
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13
Motors convert electrical energy into mechanical energy
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15
The efficiency of the drive system
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17
The load, friction and inertia resist rotation
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19
The drive torque and load torque are equal at nominal speed
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21
Variable material flow and input/output requirements
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22
The best control method is VSD
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24
Hydraulic coupling
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24
AC drive
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25
Maintenance costs
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25
Energy saving
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25
The AC drives market is growing fast
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27
The basic functions of an AC drive
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28
Technical guide No
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29
Reversing
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30
Eliminating mechanical vibrations
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31
Stall function
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32
Flying start
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33
EMC
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34
Technical differences between other systems and AC drives
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36
Factors affecting cost
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38
The motor
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38
Installation costs: throttling compared to AC drive
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40
Total cost comparison
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42
6
Guide to variable speed drives | Technical guide No
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Special attention has been given to electrical VSDs and especially to AC Drives
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No special knowledge of VSDs is required, although basic technical know-how
is required to fully understand the terms and descriptions used
...
4 | Guide to variable speed drives 7
Chapter 2 - Processes and their
requirements
Why variable speed control?
To understand why variable speed control is necessary, we first
need to understand the requirements of different processes
...
Common to both main categories, however, is the need to be
able to adjust the process
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This chapter describes the main industrial and non-industrial
processes using VSDs
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4
Processes and their requirements
Examples
Industrial:
Chemical industry
Pulp, paper, printing
Food & beverage
Power plants
Mining
Metal industry
Machine shops
Non-industrial:
Plastics
HVAC
Textiles
Water treatment
Industrial segments with VSD processes
Industrial processes are numerous, and the list above mentions
just some of the industrial segments with VSD processes
...
For example, in air conditioning applications (part of HVAC), air
flow requirements change according to the humidity and temperature in the room
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These adjustments are carried out with VSDs
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In both cases, the fans need to be adjusted according to the
main process
...
Likewise, the need for VSDs differs according to the
process
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3, EMC Compliant Installation and Configuration for a Power
Drive System
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4 | Guide to variable speed drives 33
Chapter 6 - Cost benefits of AC drives
In addition to their technical advantages, AC drives also provide
many cost benefits
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At the moment there are still plenty of motors sold without variable speed AC drives
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2 kW are sold with frequency converters, and how many
without
...
This is astonishing considering what we have seen so far in
this guide
...
But first let’s
review AC drive technology compared to other control methods
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4
Cost benefits of AC drives
Technical differences between other systems and AC drives
AC drive technology is completely different from other, simpler
control methods
...
We could also compare AC drive technology to the development
from a floppy disk to a CD-ROM
...
The benefits of both these innovations are generally well known
...
In this guide, we have
presented the benefits of the AC drive compared to simpler
control methods
...
4 | Guide to variable speed drives 35
Cost benefits of AC drives
No mechanical control parts needed
To make a proper cost comparison, we need to study the configurations of different control methods
...
In traditional methods, there is always
a mechanical part and an electrical part
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In On/Off
control, the same electrical components are needed, as well as
a pressure tank on the mechanical side
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No mechanics are needed, because all control
is already on the electrical side
...
We can still use 220 V single phase supply, when speaking of
power below 2
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36
Guide to variable speed drives | Technical guide No
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In
conventional methods there are both electrical and mechanical
components, which usually have to be purchased separately
...
Furthermore, mechanical parts wear out quickly
...
In conventional methods there are
also many electrical components
...
And last but not least, mechanical control is very energy consuming, while AC drives practically save energy
...
Technical guide No
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Only the pump itself is
not added to the costs because its price is the same regardless
of whether it’s used with an AC drive or valves
...
In an industrial environment there are
stricter requirements for valves and this increases costs
...
This is due to the 3-phase
motor used with the AC drive and the single phase motor used
in other control methods
...
Mechanical parts themselves are almost always less costly than a frequency converter, but electrical parts
also need to be added to the total investment cost
...
Only throttling in domestic use is as low
cost as the AC drive
...
Together with investment costs we need to look at installation
and operational costs
...
4
Cost benefits of AC drives
Throttling
AC drive
Installation material
20 USD
10 USD
Installation work
5h x 65 USD =
325 USD
1h x 65 USD =
65 USD
Commissioning
work
1h x 65 USD =
65 USD
1h x 65 USD =
65 USD
Total
410 USD
140 USD
Savings in installation: 270 USD!
Installation costs: throttling compared to AC drive
Because throttling is the second lowest investment after the AC
drive, we will compare its installation and operating costs to the
cost of the AC drive
...
This means twice
the amount of installation material is needed
...
To install a mechanical valve into a pipe is not that
simple and this increases installation time
...
Multiply this by the hourly rate charged by
a skilled installer to get the total installation cost
...
One hour is usually the time required in both cases
...
As you can
see, the AC drive saves up to USD 270 per installation
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Technical guide No
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75 kW
0
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1
300 USD
150 USD
Maintenance/year
40 USD
5 USD
Total cost/year
340 USD
155 USD
USD/kWh
Savings in one year: 185 USD!
Operational costs: maintenance and drive energy
In many surveys and experiments it has been proved that a 50%
energy saving is easily achieved with an AC drive
...
75
kW, with the AC drive it would be 0
...
If a pump is used
4000 hours per year, throttling would need 3000 kWh and the
AC drive 1500 kWh of energy per year
...
Here USD 0
...
As mentioned earlier, mechanical parts wear a lot and this is
why they need regular maintenance
...
In many
cases however, there is no maintenance required for a frequency
converter
...
This means that the payback time of
the frequency converter is two years
...
To retrofit an existing throttling system the pay-back
time is two years
...
4
Cost benefits of AC drives
Total cost comparison
In the above figure, all the costs have been summarised
...
Here the operational costs are rated to
the present value with a 10% interest rate
...
Most of the savings with
the AC drive come from the operational costs, and especially
from the energy savings
...
Taking the total cost figure into account, it is very difficult to
understand why only 3% of motors sold have a frequency converter
...
Technical guide No
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4
H
harbour 19
hydraulic coupling 24
I
industrial processes 13
inertia 18, 32
input power 16
interference 15, 21
inverter 14, 15, 24
IP21 33
IP54 33
L
linear ramp 30
load capacity curves 28
M
machine 11, 13, 24, 29
magnetic flux 14, 15
maintenance 24, 25, 26, 37, 40
mechanical power 16
mechanical vibrations 29, 30
motor load 32
motor losses 16
motor phase 14
motor size 16
motor stall condition 31
motor windings 14, 15
N
nuisance faults 29
O
output power 16
P
power factor 16
power loss ride-through 29, 31
power plants 22, 37
process control 25, 26, 27, 29
processing system 10
pump 24, 25, 36, 40
R
rated speed 16
Reactive power 16
reactive power 16
reactors 36
rectifier 14
reference speed 30
reversing function 29
right hand rule 14
Index
S
S-ramp 30
slip 14, 29, 32
squirrel cage motor 20, 24, 33
stall frequency 31
stall function 29, 31
stator 14
stepless control 15
T
temperature 15, 33
throttling 22, 36, 39, 40
torque 16, 17, 18, 19, 20, 28, 29,
30, 31, 32
transistors 16
V
valve 40
valves 24, 36
variable speed control 8, 21, 24
Variable Speed Drives 1, 3
voltage 14, 15, 16, 24, 27, 31
VSD 9, 15, 22, 23, 24, 25, 26
Technical guide No
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abb
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abb
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All rights reserved
...
3AFE61389211 REV C EN 12
...
2011 #15677
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Title: Note- Variables Speed Drives
Description: Interesting note on variable speed drives
Description: Interesting note on variable speed drives