Single Phase Motor Capacitor Calculator: Run & Start Sizing

single phase Motor capacitor calculator

Estimate single-phase motor run/start capacitor size from supply voltage, current, and frequency. Uses C≈k·I/V with 50/60 Hz factors and quick HP/kW rules.

single phase motor capacitor calculator

Starting capacitor This can be estimated very fast capacitor run (lF) = k(l) I(line)/V, where k = 2650 (50 Hz) or k = 3180 (60 Hz) In the case of cap-start motors select C start = 2-4 x C run; check the motor datasheet.

Formula & Table Summary:

Capacitor Sizing Formulas:

\[ C_{\text{run},50Hz} (\mu F) \approx \frac{2650 \cdot I(A)}{V(V)} \]

\[ C_{\text{run},60Hz} (\mu F) \approx \frac{3180 \cdot I(A)}{V(V)} \]

\[ C_{\text{start}} (\mu F) \approx (2\text{–}4) \cdot C_{\text{run}} (\mu F) \]

\[ \text{Heuristic: } C_{\text{run}} \approx 10\text{–}20 \,\mu F/\text{HP} \; (\approx 13\text{–}27 \,\mu F/\text{kW}), \quad C_{\text{start}} \approx 40\text{–}80 \,\mu F/\text{HP} \]

\[ \text{Selection: Choose capacitor VAC ≥ supply; verify duty (continuous vs intermittent)} \]

auxiliary winding capacitor

This Single Phase Motor Capacitor Calculator determines the large size capacitor (PSC) and star-t capacitor that it needs on single-phase induction motors. A common rule is based on the line current ( I ) of a motor (the motor must be in phase with the frequency), voltage ( V ) and frequency ( f ): In 50 Hz, 33 C run(micro F) =approximately equal to 2650I/V, in 60 Hz, 33 C run(micro F) =approximately equal to 3180I/V. Split-phase/cap-start motors have typical start capacitors that are 2or 4 times the run value. Shortcutting works, too: Run 10-20 1/HP (13-27 1/kW) at about 230 V and Start 40-80 1/HP (54-108 1/kW). Check each time on the nameplate of the motor and the manufacturer specifications; these guidelines are aimed at approximate phase shift and auxiliary-winding current typical designs PSC/cap-start). Final selection should be made based on voltage rating, temperature, and duty (continuous and intermittent) as well as surge.

50Hz capacitor calculator

Freq	V (VAC)	I (A)	C_run (µF)	C_start (µF)
50 Hz	230	2.0	23.0	46–92
50 Hz	230	4.0	46.1	92–184
60 Hz	120	6.0	159.0	318–636
60 Hz	240	3.0	39.8	80–160
50 Hz	230	—	10–20 µF/HP	40–80 µF/HP

Frequently Asked Questions - single phase Motor capacitor calculator:

How do I estimate a run capacitor for a single-phase motor?

Use C_run(µF) ≈ k·I/V with k=2650 (50Hz) or 3180 (60Hz).

How large should the start capacitor be?

Typically 2–4× the run capacitor value, intermittent duty.

Can I size by horsepower instead of current?

Yes; run ≈10–20 µF/HP, start ≈40–80 µF/HP (verify against nameplate).

Does frequency change the capacitor size?

Yes. Use k=2650 for 50Hz and k=3180 for 60Hz in C≈k·I/V.

What voltage rating should I choose?

Select a capacitor with VAC rating ≥ supply; run caps often 370–450VAC.

Are these values exact?

No, they are practical estimates. Always confirm with the motor manufacturer.

Do PSC and cap-start motors use the same capacitor?

PSC uses a continuous-duty run cap; cap-start adds a larger start cap via a switch.

What if the motor overheats or hums after replacement?

Capacitance may be incorrect or the cap faulty; recheck value, rating, and wiring.

Can I parallel capacitors to reach a value?

Yes, parallel adds capacitance (C_total = C1+C2); ensure matching voltage ratings.

Is a higher µF always better?

No. Too high can raise current and heating; match the specified/estimated value.

Tags: PSC motor capacitor auxiliary winding capacitor HP to µF converter motor capacitor µF 60Hz capacitor calculator 50Hz capacitor calculator C = 2650 I/V start capacitor sizing motor run capacitor size single phase motor capacitor calculator