A shielded transformer is a type of transformer that includes an additional metal shield between the primary and secondary windings. This shield provides an extra layer of insulation and serves to reduce the transfer of electrical noise and interference from the primary to the secondary winding. Here are some key aspects of shielded transformers:
- Electrostatic Shielding: The primary purpose of the shield is to provide electrostatic shielding. This reduces the capacitive coupling between the primary and secondary windings, which can help to prevent high-frequency noise or spikes on the primary side from being transferred to the secondary side.
- Construction: The shield is typically made of a thin layer of copper or aluminum and is grounded. It’s inserted between the primary and secondary windings and wraps around the entire core.
- Applications: Shielded transformers are particularly useful in sensitive electronic applications where electrical noise can be problematic. Examples include medical equipment, computer systems, laboratory instruments, and audio systems.
- Noise Reduction: The shield can reduce both radiated and conducted electromagnetic interference (EMI) from the transformer, ensuring that sensitive equipment downstream is not adversely affected.
- Safety: The shield can also provide an additional layer of safety by preventing any accidental connection or arcing between the primary and secondary windings.
- Cost: Shielded transformers are generally more expensive than their non-shielded counterparts due to the added materials and the complexity of construction. However, the benefits in terms of noise reduction and improved performance can justify the extra cost in many applications.
- Grounding: Proper grounding of the shield is crucial. If the shield is not grounded correctly, it can become a source of noise or interference rather than reducing it.
- Size and Weight: The addition of the shield can add slightly to the overall size and weight of the transformer.
In applications where electrical noise or interference can affect the performance of equipment, or where additional safety barriers are desirable, shielded transformers offer an effective solution. They are especially relevant in environments with a lot of electronic equipment, where EMI can become a significant concern.