Z Transform - Properties

Laplace transform - Properties

Selection Criteria (Part 1)

Relay

1.        No. and Type of contacts

2.       Rating of contacts (Pick- up Current)

3.       Voltage Rating of contact

4.       No. of operations/Life

5.       Coil Voltage

6.       AC/DC operations

7.       Package/Enclosure

8.       Assembly/Mounting

9.       Switching Time/Characteristics

10.    Contact Material

11.     Contact Sequence

12.    Coil Current

13.    Operating Environment

14.    Coil Protection

15.    Size

16.    Accessories

17.    Approvals

18.    Plug Setting Mode

19.    Radiation

MCB

1.        No. of Poles

2.       Current Rating

3.       Operating Voltage/ Frequency

4.       Operating Curve

5.       Braking Capacity

6.       AC/DC Operation

7.       Assembly/Mounting

8.       Approvals

9.       Accessories

10.    Service Life

11.     IP Protection

12.    Operating Condition

13.    Conductor Cross-section

14.    Module Width

HRC Fuse

1.        Current Rating

2.       Type

3.       IEC Size

4.       Fuse Tag/ Fixing Hole

5.       Braking Capacity

6.       Operating Voltage/ Frequency

7.       Approvals

8.       Utilization Category

9.       Fusing Factor

10.    Rated Power Dissipation

11.     Fuse Holder/ SDF Type

Contactor

1.        Rated  Current

2.       No. of Poles

3.       Operating Voltage/ Frequency

4.       Operating Category/ Duty

5.       Auxiliary Contacts/ Add-on Block

6.       Coil Type (AC/DC)

7.       Coil Voltage

8.       Medium of Arc Quenching

9.       Application

10.    Mechanical Interlock

11.     Contactor Size/ Frame Size

12.    Surge Suppressor Details

13.    Switching Frequency

14.    Operating Time

15.    Conductor Cross-section

16.    IP Protection

17.    Approvals

18.    Operating Conditions

19.    Enclosure/Mounting

20.   Mechanical/ Electrical Endurances

21.    Power Consumption of Coil

22.    Impulse Voltage Withstand

23.   Insulation Voltage

Overload Relay

1.        Relay Range

2.       Type

3.       Mounting

4.       Operating Voltage/ Frequency

5.       No. of Poles

6.       CT Details

7.       Accessories

8.       Approvals

9.       Single Phase Protection

10.    Auxiliary Contact

11.     IP Protection

12.    Conductor Cross-section

13.    OL Indication

Time Switch

1.        Operating Voltage/ Frequency

2.       Shortest Switching Time (Daily /Weakly)

3.       Power reserve

4.       Maximum Contact rating

5.       Mounting

6.       Application

7.       IP Protection

8.       Digital/ Analog

9.       Switching Contact

10.    Memory Locations

11.     Manual Over-ride

12.    Approvals

13.    Power Consumption

14.    Operating Conditions

Single Phasing Preventer

1.        Operating Voltage /frequency

2.       Mode of Operation

3.       Output

4.       Contact Rating

5.       Principle of Operation

6.       Display

7.       Trip Time Delay

8.       Voltage Unbalance (P-P)

9.       Enclosure/ Mounting

10.    Auto Restart

11.     Phase Reversal Protection

12.    Approvals

13.    Conductor Cross-section

14.    IP Protection

15.    Mechanical/Electrical Life

16.    Operating Conditions

Cable

1.        Size (Sq-mm)

2.       No. of Core

3.       Sheathing

4.       Working Voltage

5.       Conductor Material

6.       Insulation Material

7.       Armor Material

8.       Sheathing Material

9.       Application

10.     Conductor Stranding

11.     Cable Braiding

12.    Colour Code

13.    Approvals

14.    Conductor Resistance

15.    Insulation Thickness/ Dia.

16.    Current Carrying Capacity

17.    Sheath Thickness (Inner/Outer)

18.    Derating Factor

19.    Cable Shape

20.   Operating Conditions

21.    Marking

22.    Short Circuit Rating

23.   Testing

24.    Laying

25.    Bending Radius

26.   Dielectric Strength

27.    Filler

28.    Screening

29.    Armor Wire Dia.

30.   Overall Dia.

31.    Packing

32.   Communication Parameters

33.   Weight (Kg/Km)

Switch Disconnector Fuse (SDF)

1.        Current Rating

2.       Operating voltage /Frequency

3.       Fuses Used

4.       No. of Poles

5.       Short Circuit Rating

6.       Clearance/ Phase Barriers

7.       Conductor Cross-section

8.       Indications

9.       Enclosure & Mounting

10.    Approvals

11.     IP Protection

12.    Accessories

13.    Physical Size

14.    Neutral Link

15.    AC/DC

16.    Electrical / Mechanical Life

Transient Voltage Surge Suppressor (TVSS)

1.        Surge Current

2.       Operating voltage/ Frequency

3.       Back-up Fuse

4.       Lightning Protection

5.       Max. Continuous Operating Voltage

6.       Voltage Protection Level

7.       Response Time

8.       Follow Current Quenching Capacity

9.       IP Protection

10.    Short circuit Resistance

11.     Nominal Discharge Current

12.    Operating Conditions

13.    Mounting/ Enclosure

14.     Conductor Cross-section

15.    Lightning Protection Zone (LPZ)

16.    Approvals

Fans

1.        Ceiling/ Pedestal/ Wall/Exhaust/Axial Flow/Man cooler/ Roof Extractors

2.       Sweep

3.       Operating Voltage /Frequency

4.       Star Rating

5.       Duty of Operation

6.       Power Rating

7.       Bearing

8.       Colour

9.       Oscillations

10.    Speed Control / No. of Speed

11.     Speed Regulator Type

12.    No. of Blades

13.    Louver (Exhaust/ Ventilation Fans)

14.    RPM

15.    Air Delivery

16.    Guard Type

Design of Control Transformer (Case Study)

Data

Voltage Rating= 230 V/ 24 V

Frequency, f= 50 Hz

Power Rating= 100 VA

Assumptions

Flux density in the core, B = 1 wb/m²

Stacking factor for Core lamination = 0.9

Current Density in the winding, J= 2.3 A/mm²

Turns per Volt, Te = 4.6

Efficiency of the Transformer= 0.95

Core Design

Flux in the core, Øm =1/ (4.44 f Te) =1/ (4.44*50*4.6) = 9.7924 * 10^-4 Wb

Net Core Area, Ai= Øm/Bm= 9.7924 * 10^-4 /1= 9.7924 * 10^-4  m²

Gross Core Area, A_G = Ai/ Stacking factor = 10.8804 cm²

A= √A_G = 3.2986 cm

                                        

A= 3.2986 cm ≈ 3.3 cm

D= A/2 = 1.6493 cm ≈ 1.65 cm

E=D ≈ 1.65 cm

C= 3A= 9.8958 ≈ 9.9 cm

F> E or D

F ≈ 1.8 cm

B= 2D+A+2F= 10.2 ≈ 10.2 cm

Window Area = ((B-2D-A)/2)*(C-2E) ≈ 11.88 cm²

Winding Design

Primary Current, Ip = VA/ (Eff.* Vp) = (100/0.95*230) =0.4577 A

Ap’=0.4577/2.3 = 0.199 mm²

dp’= √((4*0.199)/ᴨ) = 0.5035mm

Nearest Standard Wire Size, dp= 0.508 mm (25 SWG or 24 AWG)

Ap= (ᴨ*dp²)/4= 0.2026 mm²

Turns in Primary, Tp= Te* Vp= 4.6* 230= 1058 Turns

Turns in Secondary, Ts= Te* Vs= 4.6* 24= 110.4 = 111 Turns

5 % more turns for Secondary

Ts= 1.05 Vs* Te= 115.92= 116 Turns

Secondary Current, Is = VA/ Vs= 100/24 =4.1667 A

As’=4.1667/2.3 = 1.8116 mm²

ds’= √((4*1.8116)/ᴨ) = 1.5191 mm

Nearest Standard Wire Size, ds= 1.626 mm (16 SWG or 14 AWG)

As= (ᴨ*ds²)/4= 2.0754 mm²

Space required for Primary winding= (Tp*Ap)/Space factor

Space required for Secondary winding= (Ts*As)/Space factor

Total space= (Tp*Ap)/Space factor + (Ts*As)/Space factor

                      = (1058*0.2026)/0.8 + (116*2.0754)/0.8

                      = 568.8715 mm²

25 % additional space for insulation = 1.25*568.8715= 711.0894 mm²

                                                                       = 7.111 cm²

No. of Stamping                = A/ Thickness of Stamping = (3.33 cm/ 0.33 mm)

                                                                                        = 100.9090 = 101

Width of window on Core, W= Window area/ Length of winding

                                                       = 6.9488/ (C-2E) = 1.0774 cm

W/2= 0.5264 cm

Weight of Cu wire required = Mean length of turn * (Ap*Tp +As*Ts)* Density of Cu

Mean length of turn, Tav = 4 (A+ (W/2) + (W/2))

                                                 = 17.5312 cm

Wcu = 175.312*(1058*0.2026+ 116*2.0754)* 0.0089

        = 710.0776 gm= 750 gm