- Transformer Calculator Definition: A transformer calculator is a tool that helps find key electrical values for transformers like kVA, current, and windings.
- Voltage Calculation: The voltage in transformers is calculated using Vs = Vp * Ns / Np, relating primary and secondary voltages and windings.
- Current Calculation: The current in transformers is determined by Is = Ip * Np / Ns, showing the relationship between primary and secondary currents and windings.
- Power Conservation: Power in an ideal transformer is conserved, meaning primary and secondary power are equal, though real transformers have some losses.
- Example and Applications: An example problem demonstrates calculating currents and turns ratio, illustrating step-up and step-down transformers.
The ideal transformer equation connects the primary and secondary voltages using:
Vs = Vp * Ns / Np
where
Vs [V]= the voltage at the secondary coilVp [V]= the voltage at the primary coilNs= the number of windings of the secondary coilNp= the number of windings of the primary coil
The equation that relates the primary and secondary currents of a transformer is:
Is = Ip * Np / Ns
where
Is [A]= current at the secondary coilIp [A]= current at the primary coil
Remember, the electrical power in both coils is the same.
P = Ip * Vp = Is * Vs
This shows energy conservation. In real transformers, losses make secondary power less than primary power.
Transformer Calculator Example Problem
A 50 kVA single-phase transformer has a 4000 V primary side and a 400 V secondary side. Assuming an ideal transformer, find:
- The primary and secondary full-load currents
- The transformer turns ratio.
Part 1. V1 = 4000 V, V2 = 400 V,
Transformer Rating = 50 kVA = V1× I1 = V2 × I2
Hence rearranging for I1 and I2:
Primary full-load current, I1 = (50 × (1000 / 2000)) = 25 A
Secondary full-load current, I2 = (50 × (1000 / 200)) = 250 A
Part 2. The Turns Ratio is equal to N1 / N2 = V1 / V2 = (2000 / 200) = 10
We can also calculate this using the full-load currents I1 and I2 via V2 / V1 = 10.
This is how transformer sizing is determined.
Note that if the voltage on the primary side is higher than the voltage on the secondary side, then it is a step down transformer.
If the voltage on the primary side is lower than the voltage on the secondary side, then it is a step up transformer.
