Calculate Size Of DOL and Star-Delta Starter Components

Easy way to calculate motor torque, fuse, CB, OL relay and contactor

For both DOL and Star-Delta Starter input fields are:

1. System Voltage (V)
2. Phase (1ph/3ph)
3. Type of Motor (single phase, 3-phase induction, synchronous, wound rotor etc.)
4. Motor Size (HP or kW)
5. Motor Code (A, B, C… -H)
6. Motor Efficiency (%)
7. Motor RPM
8. System P.F
9. Application of Motor (motor load in household application, hermetic refrigerant comperssor motor etc.)

According to above inputs, following starters components are calculated:

Motor Torque / Current

• Motor Rated Tourque (Full Load)
• Motor Rated Tourque (Full Load)
• Motor Starting Torque
• Lock Rotor Current IL (Min)
• Lock Rotor Current IL (Max)
• Motor Starting Current
• Motor Full Load Current (Line)
• Motor Full Load Current (Phase)

Fuse (As per NEC 430-52)

• Non-Time Delay Fuse (Max)
• Time Delay Fuse (Max)

Circuit Breaker (As per NEC 430-52)

• Instantaneous Trip Circuit Breaker (Max)
• Inverse Time Circuit Breaker (Max)

Over Load Relay Setting

• Relay Min (70% of FLC Phase)
• Relay Max (120% of FLC Phase) or
• Relay Setting (100% of FLC Line)

Contactor (for DOL starter)

• Type of Contactor
• Making / Breaking Capacity of Contactor:
• Main Contactor (100% of FLC Line):

Contactor (for Star-Delta Starter)

• Type of Contactor:
• Making / Breaking Capacity of Contactor:
• Main Contactor (58% of FLC Line):
• Delta Contactor (58% of FLC Line):
• Star Contactor (33% of FLC Line):

Transient Time Delay Setting (for Star-Delta Starter)