Transformer current calculations: The primary current is equal to the product of the secondary voltage and secondary current divided by primary current. The secondary current is equal to the product of the primary voltage and primary current divided by secondary voltage.

Primary Voltages or High Voltages (H.V) is 11000 volts. Primary Current (current on High Voltage side) is 5.25 amps. KVA = (√3. V x I) /1000= (1.732 × 11000 × 5.25)/1000=100 KVA.

Moreover, How do you calculate transformer size?

– Transformer size is determined by the kVA of the load.

– Load voltage, or secondary voltage, is the voltage needed to operate the load.

– Line voltage, or primary voltage, is the voltage from the source.

– Single-Phase has two lines of AC power.

Secondly, How do you determine the breaker size on a transformer?

Iprimary = (20 x 1000)/480 = 20,000/480 = 41.6 amps. Note: If you had a 3-phase transformer, the formula would be Iprimary = KVA x 1000/(Vprimary x 1.732). The 1.732 accounts for the 3-phase configuration. Find the circuit breaker size for the primary side of the transformer by multiplying Iprimary by 1.25.

Simply so, What is primary and secondary current?

The current in the secondary is the current in the primary (assuming a single turn primary) divided by the number of turns of the secondary. In the illustration on the right, ‘I’ is the current in the primary, ‘B’ is the magnetic field, ‘N’ is the number of turns on the secondary, and ‘A’ is an AC ammeter.

How do you calculate primary and secondary currents?

In other words, i1/i2 = V2/V1. For example, if the current and voltage drop through the secondary coil is 3 amps and 10 volts, and the voltage drop through the primary coil is 5 volts, then the current through the primary coil is 10/5 * 3 = 6 amps. So the secondary has less voltage and more current.

## 20 Related Question Answers Found

**How do you calculate transformer rating?**

Since you know kVA = V * l / 1,000, we can solve for V to get V = kVA * 1,000 / l. So you’ll multiply your kVA rating by 1,000 and then divide by the amperage. If your transformer has a kVA rating of 75 and your amperage is 312.5, you’ll plug those numbers into the equation — 75 * 1,000 / 312.5 = 240 volts.

**What are the standard sizes of transformers?**

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.

**How do you size a breaker for a transformer?**

– Transformer Primary Current (Ip) =52.49Amp and impedance is 5%

– As per above table in not supervised condition Size of Circuit Breaker= 600% of Primary Current.

– Size of Circuit Breaker = 52.49 x 600% =315Amp.

**How big are electrical transformers?**

The most common building industry standard ratings are 3, 6, 9, 15, 30, 37.5, 45, 75, 112.5, 150, 225, 300, 500, 750, and 1,000 kVA.

**How do you calculate the size of fuse for a transformer?**

A. Fuse = I*167% next size smaller if secondary current is less than 9 amp. Fuse = I*125% next size higher if secondary current is 9 amp. or higher. Fuse = I*167% next size smaller if primary current is less than 9 amp.

**How do you size a transformer?**

– Transformer size is determined by the kVA of the load.

– Load voltage, or secondary voltage, is the voltage needed to operate the load.

– Line voltage, or primary voltage, is the voltage from the source.

– Single-Phase has two lines of AC power.

**How do you find the primary current of a transformer?**

If for some reason you need a larger transformer to operate appliances, you still divide the wattage by the voltage to find the current. For a 120-volt primary, 2000-watt transformer, divide 2000 by 120 for the current (2000 Watts /120 volts =16.67 amps). For a 240-volt, 3000-watt transformer, the current is 12.5 amps.

**How do you calculate the current carrying capacity of a transformer?**

If for some reason you need a larger transformer to operate appliances, you still divide the wattage by the voltage to find the current. For a 120-volt primary, 2000-watt transformer, divide 2000 by 120 for the current (2000 Watts /120 volts =16.67 amps). For a 240-volt, 3000-watt transformer, the current is 12.5 amps.

**How do you size a 3 phase transformer?**

This is a “Two Step Division”, technique: VA / Voltage = Amperage. Three Phase Example: Using a 75 KVA Three Phase Transformer as a starting point. 75 KVA is equal to 75,000 VA. (K= 1,000) The full value in VA, 75,000 divided by 1.732 = 43,302, which is then divided by the Voltage 208V = 208.2 Amperes.

**What is the secondary current?**

(Elec.) a momentary current induced in a closed circuit by a current of electricity passing through the same or a contiguous circuit at the beginning and also at the end of the passage of the primary current.

**How do you find the primary and secondary of a transformer?**

– First turn ON digital multimeter and select continuity mode.

– Connect the test leads to the Transformer terminals.

– Read the measurement value is displayed.

– displayed multimeter value is between 300 to 700, this side is primary.

– displayed multimeter value is between 2 to 3, this side is secondary.

**How do I choose a transformer?**

– Step 1: Determine the KVA, Amperes or wattage required by the load. Determine the KVA, Amperes or wattage required by the load.

– Step 2: Find out the supply voltage.

– Step 3: Determine the voltage required by the load.

– Step 4: What is the frequency of the supply source?

– Step 5: Determine the Marcus transformer model number.

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