a pq case study - asia power quality initiative · bars are used to make wire ropes.manufacturing...

Case Study 38

Reduction in Break Down and Specific Energy Consumption by Reducing Harmonics at Usha Martin – Wire Rope Plant

A PQ Case Study

APQI (C) Copyright (2013) All Rights Reserved 1

A PQ Case Study CS 38 ENRG 14

Reduction in Break Down and Specific Energy Consumption by Reducing Harmonics at a Steel Wire Rope Plant

Case Study 38


A PQ Case Study


38 Abstract: Energy Conservation Act 2001 provides a

legal framework to embarking on energy

conservation in India. Under the act

government classified industries based on

energy consumption and these industries

are known as Designated Consumer (DC).

These DC’s are covered under Perform

Achieve and Trade (PAT) mechanism with

total energy saving target of 6.6 Million

Tonnes of Oil Equivalent by 2015. All

designated consumers are provided with

target of reducing energy consumption

that they have to meet by 2015.

Reduction in energy consumption is one

of the priorities of these DC’s.

Operating the plant without many

breakdowns is one of the top priorities for

any manufacturing facility. Increased

breakdown causes production loss, higher

specific energy consumption and reduced

profit margins. With use of drives, AC to

DC convertors and SMPS loads,

generation of harmonics is inevitable.

These harmonic current can cause

unexpected break downs and loss of

energy due to additional heat generation

in cables, motors and transformers. The

Case study below presents how a steel

wire rope mill reduced specific energy

consumption and breakdowns by filtering

out harmonics.

Case Study 38


A PQ Case Study


Introduction Usha Martin is India’s largest and world’s second largest steel wire rope manufacturers.

Manufacturing of steel wire involves number of DC motors and AC to DC convertors. Wire

bars are used to make wire ropes.Manufacturing of wire rod uses iron ore as a raw material

and it passes through different process of extracting iron from the iron ore. Wire rod is used

as a raw material to manufacture wire rope.

Schematic diagram -1 below shows production process of steel wire rope.

Transformation of wire rod in wire rope involves drawing and stranding to increase the

length of the wire rod and decrease its diameter. Surface treatment, galvanising and

patenting process are adopted during the making of wire rope to change surface properties

of the metal. In the process of drawing and stranding number of motors with different

capacities are used. Failure of one motor in drawing or stranding section can cause stoppage

of production line and loss in productivity. All these motors are equipped with drives to

control speed of the mill. Failure in drives or control cards will also reduce productivity.

In above manufacturing process various drives present in wire rope mill produces

harmonics. Presence of harmonics in the system can cause problems like:

1. Additional heat generation in the cables and neutral

2. Increase failure rate of electrical and electronics equipment

3. Increased energy consumption due to increased losses

4. Nuisance tripping of circuit breaker

Diagram – 1 Wire Rope production process

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A PQ Case Study


Background

The production facility was facing problems of breakdown of various electrical and

electronic equipments. Various type of problems and failure in the plant as reported were

as below.

A) Electronic Card Failures listed below starting with the most frequent failures.

1. VFD master drive control card (CUVC),

a) Control Card b) Power card including SMPS and IGBT

2. DC motor field controller card 3. DC motor field controller card with Thyristors 4. AC Drive Card

a) Controller card b) Power card including SMPS and IGBT

5. DC Drive Card a) Controller card b) Power card including SMPS and IGBT

6. PLC and MMI a) CPU card b) MMI controller card c) MMI display card

B) Motor Failures details and types of motor failureslisted below.

1. DC Motors. The plant has 5 to 200kw motors and out of which maximum failure happen for 5kw to 80kw motors.

a) Commutator uneven surface grooving and increased gap between slots b) Bearing wear-out and failure in the bearing-sitting-shaft and bearing-housing

at motor end cover. c) Field winding overheat, insulation puncture and interlayer short-circuit d) Armature insulation puncture

i. Equalizer winding in commutator ii. Inter-pole winding in between field winding

iii. Armature winding in slot.

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A PQ Case Study


2. Squirrel Cage IM. The plant has FHP to 315kw motors and out of which maximum failure happen for 5kw to 80kw motors.

a) Bearing wear-out and failure in the bearing-sitting-shaft and bearing-housing at motor end cover and bearing cage damage.

b) Stator winding insulation puncture c) Rotor Bar, melt open, happens occasionally and up to 11kw motors only.

3. Slip Ring IM. The plant has 18.5 to 110kw motors and out of which maximum failure happen for 18.5kw to 55kw motors.

a) Bearing wear-out and failure in the bearing-sitting-shaft and bearing-housing at motor end cover and bearing cage damage.

b) Stator winding insulation punctures. c) Rotor winding insulation punctures. d) Slip ring uneven surface grooving and increased gap between slots

C) List of Card/Motor/SWG. Failures and Nuisance Tripping.

Table -1 below shows different types of breakdowns occurring in the plant along with their frequency according to feeder transformer.

TRF Load

Process Mfg. Line

Nuisance Tripping Per 8-hr. Shift

Card Failure Per Month

Motor Failure Per Month

SWG. Failure Per Year

1. 1x3mva TRF-5

Wire Mill

2

2

6

12

1. 2x1mva TRF-1&2 2. 3x1mva TRF-3,4,5 3. 2x1mva TRF-6&8

Wire Mill

2

4

7

24

1. 1x3mva TRF-10 2. 2x1mva TRF-7&9

Wire Mill

1

3

4

12

1. 1x3mva TRF-4 2. 2x3mva TRF-7&8 3. 1x3mva TRF-10 4. 2x1mva TRF-7&9

Ropery

1-per day

1

3

---

1. 2x1mva TRF-1&2

SPD

1-per day

2-year

1

---

Table-1 Breakdown rate

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A PQ Case Study


In order to find reason behind above mentioned breakdown and failure, the plant

management carried out a detailed harmonic study of the plant. Harmonic levels were

measured at different locations in the plant. Table-2 below shows summary of harmonic

level at incomer level and different feeders in the plant.

Date / Load

3-Ph Voltage KV/volt

3-Ph Current ~ Max

%-THD-v %-THD-i (Harmonics)

MW-pk.

MW-ave.

MVAr-pk.

MVAr-ave.

PF-ave.

Hz-ave. Ref page in annex-II & CTR Remarks

* 33kv Power Source JSEB Incomer and 10mw CPP

33kv JSEB I/C

32.77 33.10 32.93

76.74 78.02 81.68

3.0% 45.0% 5

th, 7

th, 3

rd

4.30 2.45

1.85 0.79

0.96 49.96

* High Harmonics from Loads

33kv CPP I/C

32.66 32.66 32.73

177.66 170.33 171.25

6.0% 7.0% 5

th, 7

th, 3

rd

8.86 7.17

4.43 2.99

0.92 49.99

* Harmonics are within near Limits

* 3mva, 33/0.415kv TRF Load Distributions

TRF-4 Ropery

239.0 241.8 241.2

2947 3099 3011

12% 21% 7

th, 5

th, 3

rd

1975 1677

1478 874

0.89 49.99

* High Harmonics from Loads * 500/1400 =35% Cap effective * In=500A, I3=25% of In

TRF-5 Wire Mill

237.7 239.3 239.6

2648 2725 2810

15% 60% 5

th, 7

th, 3

rd

1988 1260

2043 537

0.93 50.01

* High Harmonics from Loads * 800/1600=50% Cap effective * I/C-1 (x2) & I/C (x1) LF adjusted

TRF-7 LRPC

Ropery

221.1 220.7 217.4

2128 2143 1847

11% 37% 5

th, 7

th, 11

th

1285 1034

581 457

0.92 50.00

* High Harmonics from Loads * 1 of 2 LRPC lines were OFF * 400/400=100% Cap effective

TRF-8 LRPC

Ropery

239.0 238.6 236.3

2122 2120 1453

10% 36% 5

th, 7

th, 3

rd

1260 1128

480 336

0.90 49.98

* High Harmonics from Loads * Ducati Cap burnt & removed

TRF-10 HRBC Ropery& Wire Mill

232.7 234.5 234.7

1983 2046 2002

12% 35% 5

th, 7

th

1196 1011

751 100

0.85 49.99

* High Harmonics from Loads * 200/600=33% Cap effective * 3mva, 11/0.415kv TRF from Main SS

* 1mva, 11/0.415kv TRF Load Distributions TRF-1,2

Main SS Wire Mill

245.6 246.0 246.5

1305 1252 1272

10% 33% 5

th, 7

th, 11

th

910 561

535 50

0.95 49.99

* High Harmonics from Loads * 300/600=50% Cap effective

TR-3,4,5

Main SS Wire Mill

242.9 242.6 242.9

2606 2570 2573

11% 22% 5

th, 7

th, 11

th

1905 1578

693 484

0.96 49.99

* High Harmonics from Loads * Cap ON throughout

Table-2Harmonic level at different feeders

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A PQ Case Study


Table-3 below shows IEEE-519 standard.

a1) Current Harmonic Distortion (120V- 69kV)–User’s responsibility ISC / I1 < 11 11<=h<1

7 17<=h<23 23<=h<35 35<= h THD

<20 * 4.0 2.0 1.5 0.6 0.3 5.0

20<50 7.0 3.5 2.5 1.0 0.5 8.0

50<100 10.0 4.5 4.0 1.5 0.7 12.0

100<1000 12.0 5.5 5.0 2.0 1.0 15.0

>1000 15.0 7.0 6.0 2.5 1.4 20.0

Notes The best harmonic management practice is to limit it at lowest possible volt level at its point of generations. Also user PCC at TRF secondary is always <69kv.

a2) Voltage Harmonic Distortion– TRF Sec volt; its user’s responsibility Bus voltage at

PCC Individual voltage

distortion THD Remarks

<=69 KV 69>=161 KV

>161 KV

3.0 1.5 1.0

5.0 2.5 1.5

HV system may have up to 2% THD, as in HVDC terminal that attenuates

while tapped for a user.

Notes on IEEE-519 Standard: * All power generation equipments are limited with these limits regardless of their ISC/I1 value. Odd Harmonics (I3, 5 …): Values in table are for odd harmonic limits as % of I1. Even Harmonics (I2, 4 …): Even harmonics are limited to 25% of odd harmonic limits. ISC: Short Circuit current at PCC at system fault MVA. If ISC=32kA at 3.3kv & I1=1.487kA then 8% THD limit apply. I1: Fundamental Full Load Current at PCC. If Grid IC TRF is 8.5mva 110/3.3kv; I1 =1.487kA at 3.3kv. Harmonic Number (I5, I7 …) THD Total Harmonic Distortion; say THDi (current) or THDv (voltage)

When measured values were compared with the IEEE-519 standard, it was found that at all

distribution transformers, harmonic current were higher than the limit prescribed by the

standard. The load consists of drives, PLC’s and AC to DC convertors and as seen from table

2 above, harmonics were recorded at all distribution transformers due to non linear load. As

harmonics have a tendency to flow in the upstream of the network due to low impedance,

harmonics were found at the grid incomer. The flow of harmonics is towards the grid and

can flow in the system of other plant connected on the same grid.

After carrying out the study, the top management decided to install passive harmonic filter

at the different locations as suggested by the auditor. Usha Martin took the project to install

passive harmonic filters in a phased manner.

Table-3 IEEE-519 Standard

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A PQ Case Study


Solution adopted by the plant: From the study, it came to knowledge of the plant team that the harmonic levels at

different feeder levels are very high as compared to limit specified by IEEE-519. One of the

very possible reasons for failure of various components in the plant could be presence of

harmonics. The plant team decided to mitigate harmonics by installing harmonic filter. As

the order of harmonics were same for a feeder and loading conditions were almost

constant, the plant team decided to install passive harmonic filter. The passive harmonic

filters were designed as per load current and order of harmonics.

The plant team decided to install passive harmonic filter in a phased manner. In the first

phase, the plant team installed passive harmonic filter on transformer number 4 and

transformer number 5 where presence of harmonics were maximum. Rating of the installed

harmonic filter is as below.

Transformer – 4 (1x3mva, 33kv/ 0.415kv): Passive Tuned Harmonic Filter; 2365A (incl. 30%

overload) 415v, 50 Hz 3840kvar. Tuned at 5th/7th to limit THD-v & THD-i

Transformer – 5 (1x3mva, 33kv/ 0.415kv):Passive Tuned Harmonic Filter; 3422A (incl. 30%

overload) 415v, 50 Hz 5760kvar. Tuned at 5th/7th to limit THD-v & THD-i

The plant installed these filters in the month of May – 2013. In order to assess benefits

gained by the installing harmonic filter at transformer – 4 and transformer – 5, plant team

carried out detailed analysis. The analysis was carried out for:

1. Effect on breakdown

2. Effect on energy consumption

3. Effect on production and specific energy consumption

Post Mitigation Analysis

Effect on harmonics:

After installation of passive harmonic filter at transformer 4 and transformer 5, the plant

team carried out measurement at the above mentioned feeders. Table – 4 gives summary of

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A PQ Case Study


comparison of harmonic level measured at transformer 4 and 5 with and without harmonic

filter.

Location

Without Harmonic filter With Harmonic Filter

Vthd Ithd Vthd Ithd

Transformer – 4 12% 21% 2.10% 11.20%

Transformer – 5 15% 60% 1.20% 7.20%

Transformer - 4

Figure -3A and 3B shows snapshots of voltage waveform and harmonic levels measured

without and with harmonic filter at transformer – 4. From the snapshot it can be seen that

without harmonic filter the waveform is distorted where as with harmonic filter the

waveform is more of sinusoidal nature with lower level of voltage distortion.

Table-4 Voltage and Current THD comparison

Figure – 3A Vthd and Voltage waveform without harmonic filter at TR-4

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A PQ Case Study


Figure -4A and 4B showssnapshots of current waveform and harmonic levels measured

without and with harmonic filter at transformer – 4. From the snapshot it can be seen that

without harmonic filter the waveform is distorted where as with harmonic filter the

waveform is more of sinusoidal nature with lower level of current distortion . Graph 4B

shows that 5th order harmonics increased, however graph 4A has maximum value of THD up

to 40% where as graph 4B has maximum value of THD up to 20%.

Figure – 3B Vthd and Voltage waveform with harmonic filter at TR-4

Figure – 4A Ithd and current waveform without harmonic filter at TR-4

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A PQ Case Study


Transformer - 5

Figure -5A and 5B shows snapshots of voltage waveform and voltage harmonic levels

measured without and with harmonic filter at transformer – 5. From the snapshot it can be

seen that without harmonic filter the waveform is distorted where as with harmonic filter

the waveform is more of sinusoidal nature with lower level of voltage distortion.

Figure – 4B Ithd and current waveform with harmonic filter at TR-4

Figure – 5A Vthd and voltage waveform without harmonic filter at TR-5

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A PQ Case Study


Figure -6A and 6B shows snapshots of current waveform and current harmonic levels

measured without and with harmonic filter at transformer – 5. From the snapshot it can be

seen that without harmonic filter the waveform is distorted where as with harmonic filter

the waveform is more of sinusoidal nature with lower level of voltage distortion.

Figure – 5B Vthd and voltage waveform with harmonic filter at TR-5

Figure – 6A Ithd and current waveform without harmonic filter at TR-5

Case Study 38


A PQ Case Study


Effect on breakdown:

Table -4 shows comparison of failure rate of different component in the plant before and

after installation of harmonic filter.

Component Ratings FY 13 APR 13 MAY 13 JUN 13 JUL 13 AUG 13 SEP 13 OCT 13 NOV 13

< 3 KW 14 2 1 0 0 1 0 0 0

3-5 KW 11 1 1 0 0 0 0 1 0

5-10 KW 2 1 1 0 0 0 0 0 0

10-25 KW 4 4 2 1 0 0 1 0 0

>25 KW 2 3 1 0 0 0 0 0 0

Total 33 11 6 1 0 1 1 1 0

< 1 KW 4 0 0 0 0 1 0 0 0

1-11 KW 45 2 1 0 1 0 1 0 0

> 11 KW 7 1 1 0 0 1 0 0 0

Total 56 3 2 0 1 2 1 0 0

< 1 KW 9 0 0 0 0 1 0 0 0

1-11 KW 6 0 2 1 0 0 0 0 0

> 11 KW 8 1 0 0 1 0 0 1 0

Total 23 1 2 1 1 1 0 1 0

No of Motors

Failed

No of Drives

Failed

No of PLCs

Failed

Component Failure Trend

Before HF After HF

Figure – 6B Ithd and current waveform with harmonic filter at TR-5

Table – 4 Breakdown – Before and after installation of harmonic filter

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A PQ Case Study


Table 5 shows change in annual rate of failure before and after installation of harmonic

filter.

Component

Annual failure rate

before Harmonic filter – FY 2012-13

June-Nov 2013

Failures

Extrapolated - Annual failure rate

after harmonic filter

Change in failure rate

Motors 43 4 8 -81% Reduced by 81%

Drives 52 4 8 -85% Reduced by 85%

PLC's 22 4 8 -64% Decreased by 64%

From table 4 and 5 it can be seen that after installation of harmonic filter, there is significant

reduction in breakdown of different component. Each break down result in loss of

production time in addition to replacement cost for each break down and specific energy

norms going up.

Average benefits gained by the plant due to reduction in breakdown:

1. Average monthly cost saving by INR 240,000.00 due to avoided maintenance cost

2. Average increase in production time - 98 hours per month

Effect on Electricity Charges:

Apart from reduction in breakdown, installation of harmonic filter also helped in reduction

of specific energy consumption.Table-6 shows reduction in average electricity cost on

monthly basis.

ACTUAL ELECTRICITY BILL

Months Monthly

Average - FY13

Monthly Avg Jun-Oct13

% Change

Energy Consumption – kWh

1,891,930.00

1,778,352.00 ↓ by 6%

Maximum demand – kVA

9,236.00

7,872.00 ↓ by 14.77%

Table-5 Breakdown rate – Before and after harmonic filter

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A PQ Case Study


Unit rate - INR per kWh

5.40

5.40

Demand Charges INR per kVA

235.00

235.00

Part "A" Energy Consumption

10,216,422.00

9,603,100.80 ↓ by 6%

Part "B" Maximum Demand

2,170,460.00

1,849,920.00 ↓ by 14.77%

Total (A+B)

11,957,272.00

11,453,020.80 ↓ by 4.22%

Surcharge For 110% of Contact Demand

94,000.00

- ↓ by 100%

Miscellaneous Charges (Voltage Rebate)

358,718.16

343,590.62 ↓ by 4.22%

Current D.P.S

107,980.00

- ↓ by 100%

After Date D.P.S

76,699.92

186,502.00 ↑ by 143%

Total (C)

(80,038.24)

(157,088.62) ↓ by 96%

Total (A+B+C)

11,877,233.76

11,295,932.18 ↓ by 4.9%

Rebate (PF/LF/Voltage):2% of Total (A+B)

239,145.44

229,060.42 ↓ by 4.22%

Total Assessment in Rs

11,638,088.32

11,066,871.76 ↓ by 4.9%

Total Assessment in Rslakhs

116.38

110.67 ↓ by 4.9%

While assessing change in energy consumption, production levels were also considered.

Average monthly production for the financial year 2012-13 was 10,935 tons. Average

monthly production recorded for the period of June to October 2013 was 11,632 tons. There

is increase in production by 6.4% and reduction in energy consumption by 6%. Overall

reduction in monthly average electricity bill was 4.9%.

With the reduction in energy consumption and increase in production, specific energy

consumption of the wire rod production has reduced significantly.

SPECIFIC ENERGY CONSUMPTION

Parameter Monthly Monthly % Change

Table-6 Energy cost – Before and after harmonic filter

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A PQ Case Study


Average - FY13

Avg Jun-Oct13

Finish Machine Production in tons 10935 11632 ↑ by 6.4%

KWH/Ton of Production (JSEB) 173 153 ↓ by 11.6%

Rs/Ton of Production 1064 951 ↓ by 10.6%

From the table-6 it can be seen that after installation of passive harmonic filter, finished

machine production has increased by 6.4%. One of the factors of increased productivity can

be attributed to reduced breakdowns. Apart from increase in production, there is reduction

in energy consumption. Reduction in energy consumption is due to reduction in losses

arising out of harmonic current. With increase in productivity and reduction in energy cost,

specific energy consumption is reduced by 11.6%.

The benefits gained by the plant can be summarised as:

1. Reduction in maintenance, repair and replacement cost due to breakdowns.

2. Increased production due to reduction in breakdowns

3. Reduction in specific energy consumption

Financial Analysis: Financial benefits gained by the plant after installation of harmonic filter can be classified

under two heads.

1. Reduction in specific energy consumption

2. Reduction in maintenance, repair and replacement cost of failed components

Table-7 below shows financial analysis of the investment and benefits.

Financial Analysis

Part A - Reduction in specific energy consumption Unit of Measurement

Rs/Ton of Production in FY13 1,064.00 INR/Ton

Rs/Ton of Production on 31.10.13 951.00 INR/Ton

Net Gain in Rs/Ton of Production 113.00 INR/Ton

If Avg Monthly Production remains 11,000.00 Tons

Table-6 Specific Energy Consumption

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A PQ Case Study


Avg Monthly Monitory Gain

1,242,226.00 INR

Average annual monitory gain - A

14,906,714.00 INR

Part B - Reduction in maintenance, repair and replacement

Average monthly reduction in maintenance cost 240,000.00 INR/Month

Annual reduction in maintenance cost - B 2,880,000.00 INR/Year

Total (A+B) 17,786,714.00 INR/year

Investment 9,800,000.00 INR

Simple Payback 7 Months

From the table-7 it can be seen that the investment made by the plant to mitigate

harmonics has paid back within 7 months.

Conclusion: Reduction of production cost is one of the prime concerns of any production facility. In

order to reduce operation cost, better control over manufacturing process and quality use

of variable frequency drive is becoming common practice in the industry. Apart from

utilisation of drives, PLC’s are also integral part of any manufacturing process. As drives

convert frequency, generation of harmonics cannot be avoided.

Harmonics in the plant can cause:

1. Failure of various electrical/ electronic component 2. Increased energy losses due to heat generated by harmonics

From the above case study, it can be seen that by reduction of harmonics a plant can be

benefited in more than one way. The investment carried out to install harmonic filter can be

paid back within a year. Benefits gained by the plant would be:

1. Significant reduction in specific energy consumption – monetary benefit due to reduction in energy cost

2. Improved productivity due to reduced down time 3. Reduction in failure rate of various electrical/ electronic component – Cost benefit

for replacement/repair/maintenance of failed component

Table-7 Financial Analysis

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A PQ Case Study


About the Author:

Name: Jeetendra Kumar Jain

General Manager- Usha Martin Limited, Wire & Wire Rope Division

Email: [email protected]

Mr. Jeetendra Kumar Jain is graduate mechanical engineer and MBA in operations. He is

currently heading engineering activities at Usha Martin. Apart from Engineering & Projects,

he is also looking after Safety, Environment, Risk Management, Branding, Kaizen Cell and

IMS.

Mr. Jain has successfully reduced operating cost by reducing energy cost, operating

practices and process improvements in his past assignment at Hindalco and AMCO. At Usha

Martin he initiated various energy conservation projects that also include reduction in

harmonics.

Disclaimer: The sole responsibility for the content of this document lies with the authors. It does not represent the opinion of

the Asia Power Quality Initiative and /or ICPCI/ICA network. APQI and ICA network are not responsible for any use that may

be made of the information contained therein.

mailto:[email protected]

a pq case study - asia power quality initiative · bars are used to make wire ropes.manufacturing...

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