This is a quite common question asked by many. In fact, it is necessary to know why we don’t apply DC voltage to a transformer coil. You may come across the same question during interviews too. This article can help you clear your query.
Well! Here is the answer: Before explaining what will happen if a DC voltage is applied to the transformer primary, please keep in mind a few points.
- The resistance of the transformer winding is very less.
- When we apply DC voltage to the transformer, the reactance of its winding will be zero since reactance is frequency-dependent and the frequency of a DC supply is zero.
- The flux produced by the flow of direct current will be constant.
Now let us enter into the topic.
What will really happen when a DC voltage is applied to the transformer coil?
When a DC voltage is applied to the primary winding of a transformer, due to low resistance, the winding acts as a short circuit across the terminals of the DC source that lead to the flow of heavy current through the winding resulting in overheating of the winding. Eventually, the source or the winding will be damaged. The effect of current on winding depends on the applied DC voltage, rating of the transformer, winding resistance, and how powerful the DC source is. “Nothing will happen if 5Vdc is applied to a 50KVA transformer!”.
Can we get voltage at the secondary side of a transformer when DC voltage is applied?
No, there will be no output on the secondary side. But a sudden spike can be recorded due to the initial current inrush and nothing else later.
To understand this better read: Magnetization current in transformers.
Never connect the DC supply to a transformer. For testing, the current controlled source can be connected.
- Why does a transformer not work on a dc supply?
- If the primary of a transformer were connected to a dc power source
- Why doesn’t a transformer work with the direct current?