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