Motor Engineering Calculators

Motor full-load current, starting current, voltage dip, torque, slip and pump power calculators for direct, star-delta and auto-transformer starting.

Motor calculations start with full-load current and the starting duty. Full-load current sizes the cable and protection. Starting current and the resulting voltage dip decide whether the supply can start the motor and which starting method is acceptable. Torque and slip describe what the shaft delivers. The starting calculators show how star-delta and auto-transformer starting trade starting current against starting torque.

Where to start

1. Motor Full-Load Current: Full-load current from shaft power, efficiency and power factor.
2. Motor Starting Current: Starting current and torque for direct, star-delta and auto-transformer starting.
3. Motor Starting Voltage Dip: Voltage dip at the motor bus while it starts.
4. Pump Shaft and Motor Power: Pump shaft and motor power from flow, head and efficiencies.

All 8 calculators in this category

Motors

• Motor Full-Load Current: Line current of a motor from shaft power, efficiency and power factor. Open in Elecmetric
• Motor Shaft Torque: Shaft torque from motor power and speed. Open in Elecmetric
• Induction Motor Slip: Synchronous speed and slip from frequency, poles and rotor speed. Open in Elecmetric
• Motor Starting Current: Line starting current and relative torque for direct, star-delta and auto-transformer starting. Open in Elecmetric
• Motor Output Power and Efficiency Loss: Shaft power and losses from measured voltage, current, power factor and efficiency. Open in Elecmetric
• Motor Starting Voltage Dip: Voltage dip at the motor bus while it starts, and the torque still available. Open in Elecmetric
• Pump Shaft and Motor Power: Hydraulic, shaft and motor input power for a pump from flow, head and efficiencies. Open in Elecmetric
• Star-Delta Starting: Starting current and torque with a star-delta starter compared with direct-on-line. Open in Elecmetric

Also useful here

These sit in other categories but apply to the same work.

• Fan and Pump Affinity Laws: Flow, head and power at a new speed, showing the energy saved by slowing a fan or pump. Open in Elecmetric
• Three-Phase Voltage Unbalance: Percentage voltage unbalance from the three line-to-line voltages, as used for motor derating. Open in Elecmetric

What these calculators do not cover

Cross-check: all 10 calculators listed here are compared with 90 reference calculations written separately from the engine. This confirms the arithmetic and selection rules. It does not confirm that a standard table or convention matches your standard or manufacturer data.

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