How to Select a Transformer

Single Phase Encapsulated - 50 VA to 25 KVA

For all general loads, indoors or out, including lighting, industrial and commercial applications.

Units may be banked for three phase operation

Single Phase Ventilated – 15 to 100 KVA

For all general single phase loads, indoors or out, including lighting, industrial and commercial applications.

Three Phase Encapsulated – 3 to 75 KVA

For all general three phase loads, indoors or out, including lighting, industrial and commercial applications.

Three Phase Ventilated – 15 to 1000 KVA

For all general three phase loads, indoors or out, including lighting, industrial and commercial applications.

Totally Enclosed Non Ventilated – 15 to 500 KVA

Single and three phase designed for use in dirty environments.

Drive Isolation – 3 to 990 KVA

For industrial and commercial applications with SCR-controlled adjustable speed motor

drives, and AC adjustable frequency or DC drives.

Non-Linear Three Phase – 15 to 500 KVA

For electronic loads to meet non-linear load demands caused by modern office equipment.

For indoor and outdoor applications

Buck-Boost – 50 VA to 10 KVA

For correcting voltage line drops, landscape lighting, low voltage lighting, international voltage adaptation and motor applications. Buck-boost transformers do not compensate for fluctuating line voltages.

Industrial Control – 50 to 5000 VA

For control panels, conveyor systems, machine tooling equipment, commercial sewing

machines, pumping system panels, and commercial air conditioning applications.

Lighting – 100 to 1000 watts

For use with submersible fixtures including swimming pools, water fountains, low voltage circuits near water or other shock hazards. These transformers are not submersible. Single and three phase designed for use in dirty environments.

Motor Nameplate - Meaning and details

Understanding motor’s nameplate

You can fine a nameplate of a motor in motor body. Every essential data is given on this nameplate. Some times it’s difficult to understand, but it is very important. You need this data for maintenance, installation or change any kind of equipment. Engineers should concern about this data. The information of a motor nameplate is not same for all motor. Different manufacturers give different information. But most of the case, there are 15 essential information given on motor nameplate.

1. Voltage
2. Frequency
3. Phase
4. Current
5. Power factor
6. kW or Horsepower
7. Full-load speed
8. Efficiency
9. Duty
10. Insulation class
11. Maximum ambient temperature
12. Enclosure
13. Frame
14. Bearings
15. NEMA // Service factor

Standardize Circuit Symbols

Here is some Standardize Circuit Symbols:
Click on Image to Enlarge

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4.

Cable Amepre Capacity For Motor

Simple tips for select cable size for a motor:

 When you want to select a cable for motor, you need to calculate 125% to 150% load current of motor rating current. It is necessary for the high starting ampere of motor. If you select cable as rating of motor, it should be burn within some time. So, for safety, you should select a cable over the ampere rating of the motor.  

For example, for a 3 phase 30 Kw motor has running on 400 V with Power factor 0.8 and efficiency is 80%

Here, P = 30 kw = 30 × 1000 = 30000 W

V = 400 v

Power factor, Cos θ = 0.8

Efficiency, η = 80% = 0.8

From the power law,

P = √3ηVICos θ

30000 = 1.73 × 0.8 × 400 × I × 0.8                [√3 = 1.73…]

I = 30000 / 442.88

I = 67.74

So, you need to select,

67.74 × 1.25 = 84. 675 Ampere Capacity Cable

                              Or,

67.74 × 1.5 = 101.61 Ampere Capacity Cable

Now, you can easily select cable for your motor.

DOL (Direct On-Line) Starter

Circuit Diagram of DOL (Direct On-Line) Motor Starter:

Star - Delta Motor Circuit

Motor Controlling Circuit: Star - Delta

Types of Conductor

Types of Conductor