Electric Motors
Locked-Rotor kVA Calculator
This page handles the arithmetic for locked-rotor kva while leaving room to review units, limits, and source conditions.
Check Locked-rotor kVA
Locked-Rotor kVA updates live after each input change.
The Locked-Rotor kVA equation
The formula uses Line voltage, and Locked-rotor current to produce Locked-rotor kVA. Unit mistakes usually show up as an answer that is off by a factor of 10, 100, or 1,000.
The Locked-rotor kVA value and any supporting metrics belong to this same Locked-Rotor kVA case, not to a nearby run with different inputs.
Read the Locked-Rotor kVA equation from the units on this page. A familiar symbol can shift meaning between DC, AC, energy, component, or billing work.
Sample Locked-Rotor kVA run
Using the sample values, Line voltage = 400 V; Locked-rotor current = 180 A, the primary result is 124.71 kVA.
This Locked-Rotor kVA one-input test is a scale check, showing direction and sensitivity without turning the changed case into a recommendation.
If the changed line voltage comes from a real measurement, keep the original Locked-Rotor kVA run so the source of the difference remains clear.
Source notes for Locked-Rotor kVA
Treat the Locked-Rotor kVA input panel like a short measurement log. If line voltage is assumed rather than measured, label it before copying locked-rotor kva.
| Entry | Example | Check before use |
|---|---|---|
| Line voltage | 400 V | Enter line voltage in V. |
| Locked-rotor current | 180 A | Enter locked-rotor current in A. |
If the next step shifts toward Motor Power Factor, keep that as a separate worksheet instead of forcing the numbers into Locked-Rotor kVA.
What not to assume from Locked-Rotor kVA
Use line quantities for a three-phase motor.
- Ambient temperature
- Starting current
- Drive settings
When locked-rotor kva is close to a rating, use the stricter review path instead of relying on the extra decimals shown by Locked-Rotor kVA.
Reading locked-rotor kva
When locked-rotor kva is copied into notes, include the unit and the assumption that controls the result more than display precision does.
Keep Locked-Rotor kVA tied to the motor nameplate, supply system, duty cycle, and starting condition.
Audit trail for locked-rotor kva
Record the motor nameplate, supply voltage, enclosure, duty, and whether Locked-Rotor kVA describes running or starting.
If a later Locked-Rotor kVA run changes only line voltage, label it as sensitivity work. Several changed conditions deserve a new baseline.
Keep screenshots or notes only when they identify the Locked-Rotor kVA source values. A saved final number without entries is hard to audit.
Help with locked-rotor kva
How should multiple scenarios be compared?
For Locked-Rotor kVA, keep the baseline unchanged, duplicate the case, and adjust one uncertain value at a time so the reason for the difference stays visible.
Can the default values be used as a recommendation?
No. The Locked-Rotor kVA defaults only demonstrate the form. Replace them with measured or rated values for the actual electric motors case.
When should this be run again?
Run a new Locked-Rotor kVA case when the source condition changes, such as voltage, load, rate schedule, temperature, component, connection, or period.
Why might a real measurement disagree?
A field reading for Locked-Rotor kVA can include losses, tolerance, temperature effects, waveform distortion, or instrument limits that the worksheet does not model.
Why did the answer move so much after one input changed?
Many electrical relationships are proportional, inverse, squared, or tied to a denominator. A small change in line voltage can have a visible effect when the other entries stay fixed.