Tool
Motor & VFD Calculator
Synchronous and full-load RPM from supply frequency and pole count, VFD speed/torque scaling for constant- vs variable-torque loads, belt/gear reduction, and full-load current estimation.
Motor nameplate
Supply frequency
Speed at nameplate
Synchronous RPM180060 Hz, 4 pole
Full-load RPM1750
Slip2.78 %
Power & torque
Rated power5.00 HP3.73 kW
Rated torque15.01 lbf·ft20.34 N·m
Estimated FLA (3-phase)
Full-load amps5.99 A
I = (HP × 746) / (√3 × V × η × PF). Always confirm against the motor nameplate and NEC Table 430.250 for OCPD sizing.
Synchronous RPM reference
| Poles | 60 Hz | 50 Hz | FL (typ. 3% slip) |
|---|---|---|---|
| 2 | 3600 | 3000 | 3492 / 2910 |
| 4 | 1800 | 1500 | 1746 / 1455 |
| 6 | 1200 | 1000 | 1164 / 970 |
| 8 | 900 | 750 | 873 / 728 |
| 10 | 720 | 600 | 698 / 582 |
| 12 | 600 | 500 | 582 / 485 |
| 14 | 514 | 429 | 499 / 416 |
| 16 | 450 | 375 | 437 / 364 |
VFD operation
Load type
Frequency vs base100.0 %
Sync RPM at drive1800
Shaft RPM at drive1750
Torque at drive20.34 N·m15.01 lbf·ft
Power at drive3.73 kW5.00 HP
Above base frequency (typically 60 Hz here), constant-torque loads enter constant-power region — torque falls inversely with speed. For variable-torque (centrifugal pumps / fans), torque varies with speed squared and power with speed cubed (the affinity laws).
Belt / gear reduction (driven side)
Ratio = driver / driven. Speed scales with the ratio; torque scales inversely. Apply efficiency separately for true output torque (not modeled here).
Ratio0.500 : 1
Driven RPM875.0
Driven torque40.69 N·m30.01 lbf·ft
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