Transformer Voltage Ratio
The voltage ratio of a transformer defines how the input voltage (primary) is converted into output voltage (secondary). It depends directly on the number of turns in each winding.
Voltage Ratio Formula
The voltage ratio in an ideal transformer is directly proportional to the turns ratio:
::contentReference[oaicite:0]{index=0}Where:
- Vp = Primary Voltage
- Vs = Secondary Voltage
- Np = Primary Turns
- Ns = Secondary Turns
Understanding the Relationship
- If Ns > Np → Voltage increases (Step-Up)
- If Ns < Np → Voltage decreases (Step-Down)
- If Ns = Np → Voltage stays the same (Isolation)
Step-Up vs Step-Down
| Type | Condition | Result |
|---|---|---|
| Step-Up | Ns > Np | Output voltage higher |
| Step-Down | Ns < Np | Output voltage lower |
| Isolation | Ns = Np | No voltage change |
Example Calculation
Given:
- Primary Voltage = 12V
- Primary Turns = 100
- Secondary Turns = 300
Find Secondary Voltage:
Vs = (Ns / Np) × Vp Vs = (300 / 100) × 12 Vs = 3 × 12 = 36V
Important Notes
- Voltage ratio depends only on turns ratio
- Works ideally (no losses assumed)
- Real transformers have small losses
- Higher voltage means lower current (and vice versa)
Quick Memory Trick
- More turns → More voltage
- Less turns → Less voltage
- Turns ratio = Voltage ratio
Applications
- Power supplies
- Amplifiers
- Battery chargers
- Electrical distribution systems