VFD Selection Calculator
Accurate VFD selection for motor control applications
VFD Selection Calculator
Compliant with NEMA MG 1 Standards
Results:
Motor Current (A): 0.00
VFD Power Rating (kW): 0.00
How to Use the VFD Selection Calculator
Input Motor Parameters
- Enter the motor's rated power in kilowatts (kW).
- Input the line-to-line voltage in volts (V).
- Provide the motor's power factor (PF) as a decimal (e.g., 0.85).
- Enter the motor's efficiency (η) as a decimal (e.g., 0.9).
Input VFD Factors
- Enter the Service Factor (SF) for overload capacity (typically 1.0 to 1.15).
- Input the Safety Margin (SM) for transient loads and future expansion (typically 1.1 to 1.25).
Calculate Results
- Click the "Calculate" button to get the Motor Current and VFD Power Rating.
- The "Reset" button clears all input fields and results.
VFD Selection Fundamentals
Motor Current Calculation
Calculating the motor's full-load current is crucial for sizing electrical components and ensuring the VFD can supply the necessary current without overload. This calculation considers the motor's power, voltage, power factor, and efficiency.
VFD Power Rating
The VFD's power rating must be sufficient to handle the motor's rated power, along with additional margins for potential overloads (Service Factor) and future system expansion or transient loads (Safety Margin). This ensures reliable and safe operation.
Key Formulas:
Motor Current (I) = (P × 1000) / (√3 × V × PF × η)
VFD Power Rating (kW) = Motor Rated Power (kW) × Service Factor (SF) × Safety Margin (SM)
Calculation Formulas
Motor Current (I):
I = (P × 1000) / (√3 × V × PF × η)
VFD Power Rating (kW):
VFD_kW = Motor_Rated_Power_kW × Service_Factor (SF) × Safety_Margin (SM)
Example Calculation
Consider a 15 kW motor with 400V, 0.85 PF, 0.92 efficiency, SF of 1.1, and SM of 1.2:
Motor Current (I):
I = (15 × 1000) / (√3 × 400 × 0.85 × 0.92)
I = 15000 / (1.732 × 400 × 0.85 × 0.92)
I = 15000 / 542.88 ≈ 27.63 A
VFD Power Rating (kW):
VFD_kW = 15 kW × 1.1 × 1.2
VFD_kW = 19.8 kW
Results: Motor Current = 27.63 A | VFD Power Rating = 19.80 kW