The Marine Industry

33.2.1.2 The Marine Industry

cooled equivalents. Customers often have the belief that water The requirements of this industry are:

and electricity does not mix well, and are wary of prob- lems with leaks. The exception is the offshore industry where

• Initial purchase price equipment size is paramount, and therefore, water-cooling is • Reliability standard. In general there is no perceived requirement for • Ease of maintenance, i.e. minimum component count, space-saving in majority of process plants. The desirable fea-

simple design tures often requested by customers are ease of maintenance • Size and weight of equipment

and good diagnostic facilities.

• Transformerless, water-cooled VSD equipment is always The market requirement is for cost-effective, stand-alone preferred drives at various power level from a fraction of a kW up to

Other desirable features include:

30 MW. The use of standard AC machines is desirable. How- ever, if non-standard, but simpler & cheaper machines can be

A requirement for the integration of Power Management offered an advantage could be gained. functions

• Two-quadrant operation for fans, pumps, and compres- • High volumetric power density (the smallest possible)

sors

• Remote diagnostics, to allow faultfinding by experts • Four-quadrant operation for some Test Benches onshore in critical situations • Control must allow additional functions such as temper-

Drive powers are commonly in the range of 0.75 to 5.8 MW ature protection, motor bearing temperature, flow and for thrusters, and 6 to 24 MW for propulsion. The evolution

pressure control etc.

in the commercial market is towards powers from 1 to 10 MW • There is no requirement, in general, for field weakening for propulsion. Higher powers are required for naval applica-

• The harmonics produced by the drive, imposed on tions. The package drive efficiency must be equal to, or better

the power system should not require a harmonic filter. than 96%. Noise and harmonics problems are to be considered

Harmonics must be minimized

when using PWM inverters. The supply side harmonics pro- In the Low Voltage (LV) arena, the PWM VSI is dominating duced must be capable of being filtered. Above 1 MW, power the market. In the Medium Voltage (MV) arena, there are a

converters are usually equipped with a 12-pulse supply bridge, number of viable drive solutions – Load Commutated Inverters given today’s technology.

(LCI’s) and cyclo-converters. However, there is a developing Two-quadrant operation is required in general, hence, a market for MV PWM VSI drives.

diode supply bridge is adequate. Occasional requirement for crash stops force use of dynamic brake chopper. DC Bus – can

be advantageous for supply to wharf loading equipment, but

33.2.1.4 The Metal Industries

the drive power ranges are such that commercially available The requirements of this industry are: products already adequately serve this application.

The use of standard AC machines is desirable; however, if

• Reliability – high availability

motors matched to the inverter prove to be cheaper their use • Efficiency of the equipment – long-term costs of could be preferred. Low-noise emission (acoustic and electro-

ownership

magnetic) is very important. There is no requirement for high • Low maintenance costs – (this has been a key factor in torque at low speed. Programming and expanded input and

the move from DC to AC)

33 Drives Types and Specifications 887 • Power supply system distortion – more onerous regula- TABLE 33.4 Typical example of VSD specifications

tions from the supply authorities

• Specification Initial purchase cost – very competitive market, and large drive costs have a big impact on total project costs

Variable

Application

Dynamometer application for a test bench

• Confidence in the supplier and their solution

Motor type

Induction motor

Duty cycle

Continuous at full rating. 150% overload for 1

The following is a list of desirable features:

minute every 60 minutes

Power rating

100 kW

• Programmable system drives with powerful program- Supply voltage

690 V ±5%

ming tools

Supply frequency

50 ±0.05 Hz

• Preference for air-cooled stacks, but water-cooled is Speed range

acceptable if a water-to-air heat exchanger is used

Accuracy

• Powerful maintenance and diagnostic tools

Min/Max. speed

0/1500 rpm

Torque dynamic

10 ms from 100% positive torque to 100%

• Low EMC noise signature

response

negative torque

• Ability to interface to existing automation system via Power factor

> 96% lagging at all speeds

network, Fieldbus or serial link

Efficiency

> 98% at full load

• Physical size of equipment is often not an important Performance

Fully regenerative

consideration Full torque at zero speed

Ambient

0–40 ◦ C

• Fire protection systems integral to drive equipment

temperature Supply harmonics

The main market concerns are: (a) EMC regulations, G5/3, IEEE519

Life expectancy

> 5 years

(b) effects on motor insulation of higher voltage levels, and MTBF

> 50,000 hours

(c) cooling with “Dirty” Mill water is not acceptable. The MTTR

< 2 hours

maintenance of deionized water circuits is a big issue.

IP rating

IP45

IEEE 519

IEEE recommended practices and requirements for harmonic control in electrical power systems

IEC 60146

Semiconductor converters. Specifications of basic

33.2.2 Drive Specifications

requirements

Failure to properly specify an electric VSD can result in a Adjustable speed electrical power drives systems conflict between the equipment’s supplier and the end user.

IEC 61800

Often the cost can be delayed project completion and/or loss of revenue.

In order to avoid such a problem, requirement specifications should reflect the operating and environmental conditions

33.3 Drive Classifications and

(Table 33.4). The equipment supplier and the customer need

Characteristics

to work as partners and cooperate from the beginning of the project until successful commissioning and hand over. It is Table 33.5 illustrates the most commonly used classifications advisable that the end user procures the complete drive system, of electric VSDs. In this section, particular emphases will be including system engineering, commissioning, engineering given to classification by applications and by converter types. support, from one competent supplier.

Other classifications, not listed in Table 33.5, include: It is one of the first priorities to identify applicable national

• Working voltage: Low-voltage <690 V or Medium Voltage and international standards on issues related to EMC, har-

(MV) 2.4–11 kV

monics, safety, noise, smoke emissions during faults, dust, • Current type: Unipolar or bipolar drive and vibration. Over specifying the requirements could often • Mechanical coupling: Direct (via a gearbox) or indirect result in a more expensive solution than necessary. Under

mechanical coupling

specifying the requirements result in poor performance and Packaging: Integral motors as opposed to separate motor disappointment.

inverter

As far as the end user is concerned, they need to specify Movement: Rotary movement, vertical, or linear the drive interfaces – the AC input voltage, shaft mechanical

• • Drive configuration: Stand-alone, system, DC link bus

power, and shaft speed. The torque and current are calculated • Speed: High speed and low speed from these. Frequency and power factor depends on the choice • Regeneration mode: Regenerative or non-regenerative of motor. • Cooling method: Direct and indirect air, direct water (raw For a high-power drive, it is always recommended to carry

water and deionized water)

out a “harmonic survey.” Such a survey will reveal the existing level of harmonics, and quantify the impact of the new drive

Section 33.2 deals with the subject of drives require- on the harmonic levels.

ment and specification from applications point of view, while

888 Y. Shakweh TABLE 33.5 Classifications of electric VSD

By rating • Appliances

By application By devices

By converter

By motors

By industry

• Thyristor

• AC/DC (chopper)

• DC • Power

• Fraction kW

power < 1 kW • Low

generation

• Low power performance

• Transistor

• AC/AC direct

• Induction motor

• Metal

(1 < P < 5 kW) (2Q)

(cyclo- and matrix-

(squirrel cage and

converter)

wound rotor)

• High • Gate Turn-off

• Petrochemical • Medium Power performance

• AC/AC via a DC

• Synchronous

< 500 kW (4Q)

Thyristor (GTO)

link Voltage source

motor

• Integrated Gate Commutated Thyristor (IGCT)

• Servo • Insulated Gate

• Process industry • High power Bipolar Transistor

• AC/AC via a DC

• Special motors:

1-50 MW (IGBT)

link current source

SRM, BDCM,

Stepper, Actuators, Linear motor

• MOSFET

• Mining • Marine

Section 33.5 deals with drive topologies from the point of view Bipolar/MOSFET type transistors have witnessed signifi- of motor classifications.

cant popularity in the late eighties, however, they have been replaced by the IGBT which combines the characteristics of