B Calculate MINIMUM FUSE AMPERAGE by multiplying product amperage rating by 125%. Minimum fuse amperage provides more protection for the wire but may result in nuisance blows. Example: 80A x 125% = 100A. C Choose FUSE AMPERAGE near the middle of this range.

Parallel conductor installations are covered in NEC 310.10(H) and are permitted for each phase, polarity, neutral, or grounded conductor in sizes 1/0 AWG and larger. Joining conductors in parallel is like having two or more smaller conductors connected at each end to make one larger conductor.

Motors should be fused with a time-delay fuse rated 175% of the motor’s full load operating amperage, 250% of the full load operating amperage if a circuit breaker is used. The wire to a motor must be rated to carry 25% more amperage than the motor draws when operating at full load.

The primary fuses are sized as a % over the primary current in amps according to the chart below when secondary fusing is not used. Example. You have a 2KVA (2000 VA) transformer and your primary voltage is 460VAC and your secondary voltage is 120VAC. Primary Amps = VA/VAC = 2000/460 = 4.35 amps.

The standard ampere ratings for fuses (and circuit breakers) in USA/Canada are considered 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 amperes.

If you are a residential customer and have installed a 200 A panel that is 240/120 V single phase, the utility may decide to install a transformer that is much smaller. For example, the apparent power for a 200 A at 240/120 V single-phase service is 48 kVA. The utility will not typically install a 50 kVA transformer.

For Primary Side:

1. Transformer Primary Current (Ip) =52.49Amp and impedance is 5%
2. As per above table in not supervised condition Size of Circuit Breaker= 600% of Primary Current.
3. Size of Circuit Breaker = 52.49 x 600% =315Amp.

150 KVA @ 480 3Ø = 180 amps. You can feed it with a 200 but if it’s loaded to the gills, it’ll push the 200 a bit. 150 KVA @ 120/208 3Ø = 416 amps. This would obviously overload a 400 amp panel.

How to Size a Transformer

1. Transformer size is determined by the kVA of the load.
2. Load voltage, or secondary voltage, is the voltage needed to operate the load.
3. Line voltage, or primary voltage, is the voltage from the source.
4. Single-Phase has two lines of AC power.

The transformer calculator uses the following formulas:

1. Single Phase Transformer Full-Load Current (Amps)= kVA × 1000 / V.
2. Three Phase Transformer Full-Load Current (Amps) = kVA × 1000 / (1.732 × V)
3. Turns Ratio = N1 / N2 = V1 / V2 = I2 / I1

Industry standard sizes for 480- to 120/208-volt wye transformers are commonly 15, 30, 45, 75, 112.5, 225, 300 and 500 kilovolt-amperes. There are also single-phase 277-or 480-volt transformer sizes available at 5, 7.5, 10, 15, 25, 37.5, 50, 75 and 100 kilovolt-amperes.

Formulas in spreadsheet

1. HV Full load current = VA / (1.732 · Volt)
2. LV Full load current = VA / (1.732 · Volt)
3. HV Side I2R losses = I²R · 1.5.
4. LV Side I²R losses = I²R · 0.5 · 3.
5. Total I² R lossses at Amb.
6. Total Stray losses at Amb.
7. I²R lossses at 75° C temp = ((225 + 75) · losses) / (225 + Amb.

There are different methods to improve the efficiency of transformers like loop area, insulation, coils resistance, and flux coupling. The insulation among core sheets must be ideal to prevent eddy currents.

They can utilize a higher magnetic steel grade. Manufacturers can also implement improved construction practices such as using miter joints during core lamination, or using grain-oriented electrical steel in the construction process. This can improve core loss performance, while reducing no-load core losses.

Due to the constantly changing magnetic fields, there is a loss of current in the core. One easy solution for how to reduce eddy current losses in the transformer is to make the core by stacking thin sheets together. This will decrease the eddy current and hence the losses made by it too.

Step-up transformers are used at power stations to produce the very high voltages needed to transmit electricity through the National Grid power lines. These high voltages are too dangerous to use in the home, so step-down transformers are used locally to reduce the voltage to safe levels.

3 Energy Conservation In Distribution Line: a) Optimization of distribution system: The optimum distribution system is the economical combination of primary line (HT), distribution transformer and secondary line (LT), To reduce this loss and improve voltage HT/LT line length ratio should be optimized.

In a typical power distribution grid, electric transformer power loss typically contributes to about 40-50% of the total transmission and distribution loss. Energy efficient transformers are therefore an important means to reduce transmission and distribution loss. The amorphous metal transformer is a modern example.

It’s an easy task to compare and see that LED light bulbs are truly the most energy-efficient. LED bulbs produce 90 to 112 lumens per watt. Compact Fluorescent Lamps produce 40 to 70 lumens per watt, and traditional incandescent bulb fixtures only produce 10 to 17 lumens per watt.