thruster motor variable frequency drive cmr 3 nov 2010
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Solution to Electric
Propulsion System
INTRODUCTION
CMR is a leading company that provides cost effective solution for Electric Propulsion System / Power System / Automation
System Integration & is also a manufacturer of LV Switchboard / Mcc for Marine / Offshore application. Our electric propulsion
system solution includes thruster motor, drive (VFD etc), switchboard and transformers. Our engineering team is able to provide
value added service from total system studies, design, manufacturing to commissioning.
Figure 1 Electric Propulsion System for ZJBOSMECS Hull No. S901 13,000DWT Offshore Deck Cargo Ship
CMR (Far East) PTE LTD
9 Tuas View Crescent,
Singapore 637612
Tel: +65 6268 8311
Fax: +65 6265 7443
email: sales@cmrfe.com
Solution to Electric
Propulsion System –
Drive System
INTRODUCTION
Electric propulsion system consists of a vessel’s propeller
driven by thruster motor. Variable Frequency Drive (VFD)
has become the latest trend used to change the motor speed
and frequency for the electric propulsion system in the
offshore and marine industry. Advancement of power
semiconductor components such as Insulated Gate Bipolar
Transistor (IGBT) has increased the accuracy and efficiency
in converting and controlling of electrical power supply. CMR
has involved in supplying of electric propulsion system which
includes variable frequency drive (VFD) and thruster motor
for our customer. The variable frequency drives supplied by
us include Active Front End (AFE) design which is the
current-state-of-the-art.
Figure 2 Marine Variable Frequency Drive
There are several significant advantages offered by VFD when
compared to other system. The pivotal characteristic of VFD
is the negligible harmonic distortion produced especially
when using Active Front End (AFE) technology. Besides that,
it has near unity power factor. AFE variable frequency drive is
able to operate at 4 quadrants which include motoring and
braking mode. From economic point of view, VFD electric
propulsion system also optimizes diesel engine fuel
consumption which in terms reduces the operation cost.
Figure 3 Electric Propulsion System supplied by CMR for the ZJBOSMECS Hull No. S901 13,000DWT Offshore Deck Cargo Ship
• Benefits of Variable Frequency Drive (VFD)
•Low Harmonic Distortion (especially when using AFE)
•High Power Factor
•Energy Reversibility
•Modular unit construction
•Reduce mechanical stress on thruster motor
•Lowest starting current of any starter type
•Optimal fuel consumption of diesel engine
•Vector control (2 or higher level rectifiers and inverters) via fibre optics using IGBT
VARIABLE FREQUENCY DRIVE WORKING PRINCIPLE
Figure 4 Topology of an Active Front End VFD
Motor Speed is depending on the frequency by below
formula. When the frequency is varied, the motor speed will
change accordingly. This is the fundamental principle used
by variable frequency drive to control motor speed.
𝑆𝑝𝑒𝑒𝑑 =𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 (𝐻𝑧) × 120
𝑁𝑜. 𝑜𝑓 𝑃𝑜𝑙𝑒𝑠
RECTIFIER
First, rectifier in VFD converts the AC power supply to DC
power supply. The DC bus link voltage is regulated using
diode, silicone controlled rectifier (SCR), etc. Active Front
End using Insulated Gate Bipolar Transistor (IGBT) to
converts the AC sinusoidal waveform. This active front end
design has significant advantage in the harmonic issue when
compared with other semiconductor rectification which shall
be explained later. Capacitor is used to smooth the DC link
voltage. Constant DC bus bar voltage ensures that the VFD
is able to tolerate input power supply fluctuation.
INVERTER
After conversion of power supply from AC to DC, the drive
then convert back DC power supply to AC with the precise
control of IGBT. The technique used in the conversion of
DC power supply is called pulse wave modulation (PWM).
PWM is a way of delivering power supply through a series
of rectangular pulses. Pulse width modulation uses the
advantage of power semiconductor device (IGBT) to switch
ON and OFF at high switching frequency. The AC output
voltage will be determined by the pulse width. Lower AC
voltage is formed by narrower pulses and higher voltage is
formed by wider pulses. The inductance of the motor will
function like a filter to smoothen the pulses into a smooth
AC current waveform.
Figure 5 Working Principle of a Variable Frequency Drive
DRIVE FEATURES
HARMONIC
Harmonic distortion happened when the AC current to the
load distorted from ideal sinusoidal waveform. Harmonic
current is generated by the input rectifier in the AC drive.
Harmonic content can result in excessive stress on
components connected to the same supply line. Harmonic in
the voltage waveform applied to induction motor can cause
currents to flow in both stator and rotor. This can increase
the winding and core losses as this current will not
contribute towards output torque. The active front end
technology significantly minimizes the harmonic distortion
in the AC power supply. When using active end
configuration, PWM is used to create a sinusoidal back
EMF. With accurate sinusoidal PWM modulation, the drive
controls the current so that it is in phase with the input
power supply. This will remove the need of harmonic filter
and reduces the generator sizing requirement.
Figure 6 Example of Harmonics Distortion Waveform using 6-pulse
variable frequency drive
REGENERATIVE MODE
The use of active front-end rectifier enables regenerative
power supply flow back into the power supply (4-quadrants
operation). This bidirectional flow of power supply will able
to recover energy. During the regenerative mode, power
flow from motor to the drive. The DC bus link is charged by
the regenerative power. The drive will then generate a PWM
waveform back to the input power supply.
POWER FACTOR
For a controlled rectifier using SCR, the power factor
depends on the firing angle for the inductive load. During
normal rectifier operation, the supply side will see the
rectifier drawing lagging reactive current as only delayed
firing occur in the rectifier mode. Advance firing is not
allowed as the SCR will be reversed biased and there will be
no conduction through the thyristor.
Low power factor is undesirable as it results in losses and
use of large transformer and generator. Active front end
VFD helps to improve the power factor. The bus voltage is
regulated at a level higher than the input voltage by boost
action of the PWM bridge. The diodes will not conduct as a
full wave rectifier and transistor will be used to control
current. Thus, it is able to provide a sinusoidal input current
with a power factor near unity power factor.
SOFT STARTER
A VFD is the ideal soft starter for induction motor since it
provides the lowest inrush of any starter type. Direct-on-line
starter often draws ~6 time full load current (FLA). During
starting, power factor of the current is very low as the actual
power delivered is small (low speed, high torque). The
voltage drop caused in the supply source is therefore at
maximum. This disturbance can greatly affect other
equipment using the same supply line. When using VFD,
motor will be started by delivering power at low frequency
and thus no high current is required.
-2
0
Am
plit
ud
e
Time
Harmonic Distortion
Fundamental 5th Order
7th Order 11th Order
Resultant Waveform
INGEDRIVE®
INGEDRIVE® is a family of low- and medium-voltage
modular AC drives designed for demanding single-motor or
multi-motor applications handling and controlling
synchronous, asynchronous-induction, and permanent
magnet motors. These drives are suitable for four-quadrant
operation, namely, driving and brakng in both rotational
directions.
INGEDRIVE® is designed to be a highly-efficient drive
which significantly reduces energy consumption. Its
modular design enables it to cover a wide range of powers
and voltages while its intuitive structure makes it easy to use
and maintain.
Years of experience have made it possible to incorporate
two- and three-level advanced vector control into low- and
medium-voltage rectifiers and inverters, always using latest
generation semiconductors. The powerful CCU (Converter
Control Unit) communicates with power stacks via optic
fibre. The result is a compact, flexible, safe, and user-
friendly solution.
INGEDRIVE® is available with power ratings up to
27MVA, from 400V to 690V in low voltage and 2.3kV to
4.16kV in medium voltage, offering great performance,
robustness, reliability and long life expectance. Modular
design upon which the INGEDRIVE® family is based
makes it possible to design a “Custom-Made Configuration”
for each client and application.
Flexibility in design thanks to the combination of base
modules (power stacks), which allows you to choose
between DFE (6, 12, 18 or 24 pulses) and AFE (Active
Front End) topologies and different inverter modules for
single- or multi-motor solutions according to client
requirements.
The entire INGEDRIVE® converter family complies with
the most stringent international standards. The high quality
of the equipment enables INGEDRIVE® to attain
certification from the most renowned classification bodies,
such as Lloyd’s Register, DNV, ABS and BV.
Figure 7 Ingeteam 2800kW 690V AFE Variable Frequency Drive
Figure 8 Inner view of Ingeteam 2800kW 690V AFE Variable Frequency
Drive
Solution to Electric
Propulsion System –
Thruster Motor
INTRODUCTION
Thruster Motor, which normally controlled by drive system, is used to drive propeller in the electric propulsion system. Below
diagram indicates the main features of the induction motor supplied by CMR and its partner, Indar Electric. The motors are
designed and manufactured following the most common international standards such as CEI, NEMA, VDE and the special
requirements of the main certifying entities like BV, LR, DNV, GL, ABS, RINA. Its modular design can easily adapt it to the
customer requirements.
Figure 9 2500kW Azimuth Thruster Motor (horizontal design) for
ZJBOSMECS Hull No. S901 13,000DWT Offshore Deck Cargo Ship
Figure 10 1120kW Bow Thruster Motor (vertical design) for ZJBOSMECS
Hull No. S901 13,000DWT Offshore Deck Cargo Ship
Induction Motor
•Rated power ranging from 400kW to as high as 15MW.
Power from 400kW up to 15MW
•The induction motor supplied range from low voltage to medium voltage.
Voltage from 690V up to 15kV
•Vertical and horizontal design suitable for bow thruster motor and azimuth thruster motor.
Horizontal or vertical design
•Able to provide protection up to IP65 for induction motor
Different degree of protection
•Air ventilated design or sea water cooling system can be used as per customer requirement.
Different types of cooling systems (sea water cooling etc)
•The thruster motor has proven to work well with converter/inverter
Direct power or with converters.
•Wide variety of application which include propulsion system, pump drives, deck machinery etc.
Application: Main electrical propulsion and bow thrusteter
INDUCTION MOTOR WORKING PRINCIPLE
Most of the industrial applications use induction motor when compare to other type of motor alternatives as it is more rugged, low
cost, simpler and easily maintained. Three phase induction motor can be further classified into squirrel cage or wound rotor motor.
The two main components of the induction motor are stator and rotor as shown in the picture below.
Figure 11 Manufacturing Rotor
Figure 12 Rotor and Stator
A series of low resistance winding attached to motor frame formed motor stator. When voltage, V1 is applied across the winding,
magnetic field is formed by the AC current passing through. The rotor is comprised of several thin bars mounted in laminated
cylinder. The bars are arranged to be horizontally and almost parallel to the rotor shaft. Rotor and stator are separated by air gap
for rotation. EMF is induced in the rotor by the magnetic flux formed by the stator according to Lenz’s law. Hence, current, Ir is
produced in the rotor bars. This current will then induced magnetic field which will have opposite polarity when compared to
stator magnetic flux. Interaction between stator and rotor magnetic fields will then produce the torque. Motor will rotates in the
resultant torque direction.
Figure 13 Equivalent Circuit for Squirrel Cage Induction Motor
Generally, for induction motor controlled by variable frequency drive, it will operate at constant torque range up to base speed. In
the constant torque mode, voltage/frequency is kept constant so that the air gap flux density remains constant. After that, motor
will run at field weakening zone which is constant power mode. During this mode, torque is reduced as it is inversely
proportionate to the frequency.
0 0.5 1 1.5
Frequency, f/fN (% of rated frequency)
Motor Torque and Power
Torque
Power
INDAR ELECTRIC
Indar Electric, an Ingeteam company, has worked for over sixty years in the design, manufacture and supply of electrical rotating
machines. Indar Electric has won recognition and prestige for the reliability of its machines in the most adverse working
conditions. One of the most important features of Indar Electric is the quality that is offered in the products and services, backed
up by ISO 9001 and 14001 certification and the high level of involvement of all the personnel. The technical department of Indar
is staffed by highly qualified personnel and is equipped with the most advanced computer resources for the design and
development of the motors and generators. The calculation programs used in their design are based in advanced electromagnetic
and mechanical simulation tools (mechanical finite elements, electromagnetic flows and fluid dynamics simulators. Beside
asynchronous motors, Indar Electric also manufactures synchronous motors, submersible motors and dc motors. Submersible
motor with power from 1,000kW up to 10,000kW and voltage from 690V up to 15kV, used as direct or indirect pump drives in
dredgers and cutters (degree protection of IP68).
Figure 14 Electromagnetic Design
Figure 15 Finite Elements Design
Figure 16 Thermal Design
Figure 17 INDAR 3,800kW, 1000/1,200rpm, 3.3kV Diesel Electric
Propulsion Motor
Figure 18 Asynchronous motor to drive discharge pump to the land
Figure 19 Indar 1320kW, 353rpm, 3x690V, double AC motors. Low speed double propulsion motors with double stator and rotor in same housing.
Solution to Electric
Propulsion System –
Transformers
INTRODUCTION
Power transformers supplied by CMR range from LV to MV transformers. Transformer product can be either single phase or three
phases with operating frequency of 50Hz/60Hz. The dry type transformer produced is suitable for marine industry purpose. The
transformers are manufactured to conform to ISO 9001: 2000 certified by Det Norskrre Veritas (DNV) Cert. No. 0459-2003-AQ-
SIN-RVA. It is tested accordance to IEC 60726.
Optional protection devices can be added according to customer requirement. These include thermal protection devices,
thermister, digital temperature controller, relays. Special design measures are implemented to reduce the inrush current such as
high grade iron core with high saturation to prevent core saturation during startup. Below are some transformers supplied by us.
Figure 20 1,500kVA Transformer, 690V/450V
Figure 21 200kVA Transformer, 440V/240V
Figure 22 Trasfor 500kVA 690V to 440V Transformer
Solution to Electric
Propulsion System –
Switchboard
INTRODUCTION
CMR is a manufacturer of LV switchboard / MCC for Marine / Offshore application. CMR provides custom design switchboards
for our customer base on Siemens SIVACON 8PT switchboards. SIVACON is a type-tested switchgear and control gear assembly
(TTA) whose physical characteristics were designed in the test laboratory both for normal operating conditions and for fault
situations. Conclusive type tests assure maximum of reliability and personal safety. As a power distribution board, SIVACON is
available throughout the world and can be used in all power levels up to 7400A, as withdrawable as well as plug in and fix
mounted units.
Type-tested standard modules (temperature rise test, dielectric properties test, short-circuit withstand strength test, creepage distance, clearance, mechanical operation, degree of operation verification )
3 and 4 poles busbar system up to 7400kA
Rated peak withstand current Ipk up to 375kA
SIVACON has passed the following verification tests as detailed in IEC 60439-1, DIN EN 60439-1 (VDE 0660 Part 500).
Deep switchgear compartment for universal installation
Modular structure of device compartment
Single-front and back to back installation
Figure 23 SIVACON versatile low-voltage switchboard
Figure below shows the 690V main switchboard manufactured by CMR using the SIVACON for hull no. s901 vessel.
Figure 24 690V MSB for Hull No. s901 vessel.
SIVACON low voltage switchboard featuring withdrawable-unit design which is highly available standard solution for motor
control centers. This version offers the required degree of power supply flexibility and is particularly suitable for the frequently
changing requirements of the industry. Rapid replacement without interrupting the operation is one of the main advantages of its
design.
Figure 25 Motor-Control-Center SIVACON in withdrawable-unit design
Below are some of the projects handled by CMR which involve manufacturing switchboard.
Figure 26 Switchboards manufactured by CMR
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