Free · Physics models
Synchronous-Speed Motor Torque Reference
Calculate synchronous speed, induction-motor slip and torque referenced to synchronous speed.
- Formula & worked example
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Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
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Formula and method
rpm noload = 1800.0000 rpm; torque = 5.3051648 nm; slip = 2.7777778 perc.
ns = 120 f/p; Tref = 60 P/(2π ns); slip = (ns−nload)/ns.
Worked example
Enter these known values and leave the other values blank.
- Supply frequency
- 60 Hz
- Number of poles
- 4
- Power
- 1000 W
- Motor speed with load
- 1750 rpm
- Synchronous speed
- 1800 rpm
- Torque at synchronous reference speed
- 5.3 N·m
- Slip
- 2.778 %
Assumptions and limitations
- Calculate synchronous speed, induction-motor slip and torque referenced to synchronous speed.
- The torque branch uses synchronous speed, even when loaded RPM is provided. It is a reference torque, not the actual shaft torque at the loaded speed. For shaft torque use P divided by loaded angular speed.
- Power is mechanical power in this arithmetic relationship, not electrical input power. Pole count must be a positive even integer; supply frequency and RPM for the same operating state.
- Inputs and inverse outputs share the displayed unit selectors. Clear a known field to solve for it, and lock quantities that must remain fixed. Singular inverses may have no finite result.
Common questions
Does this include motor efficiency?
No. Mechanical power must already be known; electrical input needs efficiency conversion separately.
Is no-load speed exactly synchronous?
The control represents the ideal synchronous field speed. A real induction rotor usually has some no-load slip.
References
Calculate synchronous speed, induction-motor slip and torque referenced to synchronous speed. The torque branch uses synchronous speed, even when loaded RPM is provided. It is a reference torque, not the actual shaft torque at the loaded speed. For shaft torque use P divided by loaded angular speed. Power is mechanical power in this arithmetic relationship, not electrical input power. Pole count must be a positive even integer; supply frequency and RPM for the same operating state.