Welcome to Unitrafo's calculation help
Below you will find modules for useful calculations related to transformers. Change the pre-filled values to adapt the calculations to your needs. You can also download and save the calculation result as a pdf file.
Are you missing a calculation? Please let us know via our contact page.
Calculate and compare costs of energy losses
Cast Resin
Older DIN standard
Lowest lifetime cost- No-load loss
- – W
- Load loss
- – W
- Annual no-load energy loss
- – kWh
- Annual load energy loss
- – kWh
- Annual energy loss
- – kWh
- Annual energy cost
- – EUR
- Lifetime savings compared with Older DIN standard
- – EUR
- Lifetime savings
- – %
- Lifetime energy cost
- – EUR
MiljöEko2
Lowest lifetime cost- No-load loss
- – W
- Load loss
- – W
- Annual no-load energy loss
- – kWh
- Annual load energy loss
- – kWh
- Annual energy loss
- – kWh
- Annual energy cost
- – EUR
- Lifetime savings compared with Older DIN standard
- – EUR
- Lifetime savings
- – %
- Lifetime energy cost
- – EUR
MiljöEko3
Lowest lifetime cost- No-load loss
- – W
- Load loss
- – W
- Annual no-load energy loss
- – kWh
- Annual load energy loss
- – kWh
- Annual energy loss
- – kWh
- Annual energy cost
- – EUR
- Lifetime savings compared with Older DIN standard
- – EUR
- Lifetime savings
- – %
- Lifetime energy cost
- – EUR
MiljöPlus
Lowest lifetime cost- No-load loss
- – W
- Load loss
- – W
- Annual no-load energy loss
- – kWh
- Annual load energy loss
- – kWh
- Annual energy loss
- – kWh
- Annual energy cost
- – EUR
- Lifetime savings compared with Older DIN standard
- – EUR
- Lifetime savings
- – %
- Lifetime energy cost
- – EUR
Oil insulated
Older DIN standard
Lowest lifetime cost- No-load loss
- – W
- Load loss
- – W
- Annual no-load energy loss
- – kWh
- Annual load energy loss
- – kWh
- Annual energy loss
- – kWh
- Annual energy cost
- – EUR
- Lifetime savings compared with Older DIN standard
- – EUR
- Lifetime savings
- – %
- Lifetime energy cost
- – EUR
MiljöEko2
Lowest lifetime cost- No-load loss
- – W
- Load loss
- – W
- Annual no-load energy loss
- – kWh
- Annual load energy loss
- – kWh
- Annual energy loss
- – kWh
- Annual energy cost
- – EUR
- Lifetime savings compared with Older DIN standard
- – EUR
- Lifetime savings
- – %
- Lifetime energy cost
- – EUR
MiljöMax
Lowest lifetime cost- No-load loss
- – W
- Load loss
- – W
- Annual no-load energy loss
- – kWh
- Annual load energy loss
- – kWh
- Annual energy loss
- – kWh
- Annual energy cost
- – EUR
- Lifetime savings compared with Older DIN standard
- – EUR
- Lifetime savings
- – %
- Lifetime energy cost
- – EUR
Transformer effect
The calculation tool below provides a rough estimate of the minimum power (apparent power S) your transformer needs to be rated for. Enter the current values for the connection voltage Un in volts and the current I (electrical load) in amperes. The number of phases is almost always 3, but the calculation tools can also be used for single-phase systems.
As a general rule, choose a transformer with a capacity greater than the apparent power. For example, if your calculation yields an apparent power of 799.5 kVA, choose a transformer with a capacity of at least 800 kVA.
There are also other factors to consider when selecting a transformer. You are therefore always welcome to contact us to help you make the right choice.
Losses - Load
By determining the actual load on a transformer, you can also calculate the losses that occur in practice. This is therefore a very important parameter when selecting a transformer.
Idling losses (Po) are always present, so they remain constant regardless of load, which means it is, of course, important that they be as low as possible. Load losses (Pk) vary exponentially with the load, which means, for example, that at 50% load, you only have 0.25, or 25% of the specified losses at that load. At low loads, these losses are therefore not as significant as the no-load losses. At high loads, however, the opposite is true: the higher the load, the more significant the load losses become.
With the tool below, you can easily see what losses you’ll incur at different load factors. However, a rule of thumb is to aim for a load factor of about 70%. This ensures optimal utilization of the transformer and good efficiency. You should avoid very high or very low load factors, as these usually indicate that the wrong transformer was selected.
Efficiency & Voltage drop
A transformer’s efficiency generally increases with its size. A smaller electronic transformer may have an efficiency of about 50%, while a larger distribution transformer in a power grid typically has an efficiency of 98% or higher. Since 2015, the efficiency of larger transformers installed within the EU has been regulated by the so-called “Ecodesign Directive.” In short, this means that only transformers that meet the specified efficiency requirements may be installed.
The voltage drop of a transformer is important to know because it affects how well the electrical system in which the transformer is installed works. Thus, a too high voltage drop can cause the voltage on the secondary side to be too low, which in turn can impair the operation of connected equipment, or that, for example, motors do not start.
With the calculation tool below, you can easily calculate both the efficiency and the voltage drop of the transformer you're interested in—or perhaps one you already own but are thinking about replacing.