Transformer Voltage Drop Calculator
Calculate voltage regulation and losses for single phase and three phase transformers
Transformer Voltage Drop Calculator
Compliant with IEEE C57.12.00 Standards
Results:
Voltage Drop (V): 0.00
Voltage Drop (%): 0.00
Secondary Terminal Voltage (V): 0.00
Voltage Regulation (%): 0.00
Power Loss (kW): 0.00
How to Use Transformer Voltage Drop Calculator
Single Phase Transformers
- Select "Single Phase" configuration
- Enter primary voltage (line-to-neutral for single phase)
- Input secondary voltage rating
- Specify transformer kVA rating
- Enter actual load current in amperes
- Input power factor of the load (0.1 to 1.0)
- Enter transformer impedance percentage (typically 2-6%)
- Input resistance percentage (typically 1-3%)
Three Phase Transformers
- Select "Three Phase" configuration
- Enter primary line-to-line voltage
- Input secondary line-to-line voltage
- Specify transformer kVA rating
- Enter actual load current per phase
- Input power factor of the load
- Enter transformer impedance percentage
- Input resistance percentage
Understanding Results
- Voltage Drop: Actual voltage reduction in volts and percentage
- Terminal Voltage: Actual voltage available at secondary terminals
- Voltage Regulation: Percentage change from no-load to full-load
- Power Loss: Energy lost as heat in transformer windings
- Good regulation is typically below 5% for power transformers
How to Calculate Transformer Voltage Drop
Voltage Drop Components
Transformer voltage drop consists of:
- Resistive Drop: I × R × cos(φ) - due to winding resistance
- Reactive Drop: I × X × sin(φ) - due to leakage reactance
- Total Drop: Vector sum of resistive and reactive components
- Load Factor: Ratio of actual load to rated load
Key Parameters
- Impedance (Z%): Total impedance as percentage of rated voltage
- Resistance (R%): Winding resistance as percentage
- Reactance (X%): X% = √(Z² - R²)
- Power Factor: Cosine of phase angle between voltage and current
Step-by-Step Calculation Example
Given: 500 kVA, 11kV/400V, 3-phase transformer
Load Current: 720A, Power Factor: 0.8, Z%: 4%, R%: 1.2%
Step 1: Calculate reactance percentage
X% = √(Z² - R²) = √(4² - 1.2²) = √(16 - 1.44) = 3.82%
Step 2: Calculate load factor
Rated Current = 500,000 ÷ (√3 × 400) = 721.7A
Load Factor = 720 ÷ 721.7 = 0.998
Step 3: Calculate voltage drop percentage
VD% = Load Factor × (R% × cos(φ) + X% × sin(φ))
VD% = 0.998 × (1.2 × 0.8 + 3.82 × 0.6) = 0.998 × (0.96 + 2.29) = 3.24%
Step 4: Calculate actual voltage drop
Voltage Drop = 400V × 3.24% = 12.96V
Result: Terminal Voltage = 400 - 12.96 = 387.04V
Calculation Formulas
Single Phase:
VD% = (I/I_rated) × (R% × cos(φ) + X% × sin(φ))
Three Phase:
VD% = (I/I_rated) × (R% × cos(φ) + X% × sin(φ))
Reactance:
X% = √(Z%² - R% ²)
Power Loss:
P_loss = I² × R × (I/I_rated)²
Where:
VD% = Voltage drop percentage
I = Load current (A)
I_rated = Rated current (A)
R% = Resistance percentage
X% = Reactance percentage
cos(φ) = Power factor
sin(φ) = √(1 - cos²(φ))
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