Transformer Performance Parameters Introduction – No-load Current and No-load Loss
When we previously published the parameters of various transformers, we introduced the no-load current and no-load loss of transformers in detail each time. Today, we will introduce the meaning and characteristics of these two points in detail. We hope that through the introduction of these two points, you can better select transformers and understand how to select these parameters. If you want to know how to select these parameters or how to communicate with transformers, you can read our article “How to Select a Transformer Based on its No-load Current and No-load Loss?”
1. Meaning
(1) Standard definition of no-load current and no-load loss: When the rated voltage at the rated frequency is applied to one winding of a transformer and the other windings are open, the current flowing through that winding is called the no-load current. The active power absorbed by the transformer from the power source at this time is called the no-load loss.
The unit symbol is: KW. No-load loss is usually expressed as a percentage of the rated current.
(2) Actual measured no-load current and no-load loss. The no-load current measured according to standard methods is not actually the true core excitation current, but rather a composite current flowing through the winding.
The composite current includes resistive, capacitive, and inductive components; only the inductive component is the true core excitation current.
The core excitation current is much larger than the no-load current measured according to standard specifications. Similarly, the no-load loss measured according to standard specifications is not the core excitation loss, only the deviation is smaller than the no-load current.
2. Characteristics The true excitation current and excitation loss reflect the following quality factors of the core:
(1) Material properties of the silicon steel sheets
(2) The overlapping method of the core sheets (direct seam, oblique seam, and step overlap of oblique seams and installation angle).
(3) The manufacturing process of the core (including the size of the burrs on the cut, the accuracy of the core quality, the size of the gaps between the sheets, and the tightness of the binding). (4) Magnetic flux density under working voltage, etc. These are the two types we have explained. You can analyze them from the principle. Only by understanding the principle of these two parameters can you better produce and select transformers.
Post time: Dec-15-2025
