Motor calculator
Hanapin ang motor full load current, starting current at torque.
Subukan ang isang job 6
Nilalagyan ng halimbawang value ang bawat job. Palitan ang mga ito ng sarili mong value.
- Size a motor circuitThe full load current of an 11 kW motor at 400 V.
- Find starting current of a 55 kW motorThe direct-on-line starting current at 400 V.
- Find the speed of a six-pole motorThe shaft speed of a six-pole motor at 3 % slip.
- Find the torque of a 7.5 kW motorThe full load torque of a four‑pole 7.5 kW motor.
- Check a single‑phase pump motorThe current of a 2.2 kW single‑phase motor.
- Find the speed of a two‑pole motorThe speed of a 4 kW two‑pole motor at 50 Hz.
Mga input
Worked example gamit ang mga default na input.
- Shaft power
- 15 kW
- Mga phase
- Three phase
- Voltage
- 400 V
- Power factor
- 0.85
- Efficiency
- 0.9
- Mga pole
- 4
- Frequency
- 50 Hz
- Slip
- 3 %
Full load current
28.3A
- Starting current, DOL
- 169.81A
- Synchronous speed
- 1,500rpm
- Shaft speed
- 1,455rpm
- Full load torque
- 98.45Nm
Design aid lang ang resultang ito. I-verify ito laban sa kasalukuyang standard.
Mga hakbang ng kalkulasyon
- Full load currentResulta28.3A
- Synchronous speed1,500rpm
- Shaft speed1,455rpm
- Full load torque98.45Nm
- Starting current169.81A
Tungkol sa calculator na ito
How this is calculated
The tool finds the running and starting current of a motor, with its speed and torque. It works from the shaft rating, the voltage, the power factor, the efficiency and the number of poles. It reads no table, so it cites no clause.
- Full load current. The tool divides the shaft power by the efficiency. That gives the input power. It divides the input power by the power factor. It then divides by the voltage, and on three phases by the square root of three.
- Synchronous speed. It multiplies the supply frequency by 120 and divides by the number of poles.
- Shaft speed. It reduces the synchronous speed by the slip you enter, as a percentage.
- Full load torque. It divides the shaft power by the shaft speed, with the usual constant for rpm.
- Starting current. It multiplies the full load current by 6. This assumes a direct-on-line start.
Worked example
- 15 kW four‑pole motor at 400 V. The power factor is 0.85, the efficiency is 0.9 and the slip is 3 %. The full load current is 28.3 A. The synchronous speed is 1,500 rpm. The shaft speed is 1,455 rpm. The full load torque is 98.45 N·m. The direct-on-line starting current is 169.81 A.
Limits
The factor of 6 is a general assumption. A real motor can draw more or less. Read the nameplate or the data from the maker when you have it. A soft starter or a drive gives a lower starting current, and the tool does not model them.
The tool does not size the cable, the breaker or the overload relay. It does not check the voltage drop at start. The slip is an input. It is not calculated from the load.
See also: Motor full load current, 11 kW at 400 V, Motor starting current, DOL, 55 kW and Motor circuits and starting.
Mga tanong
Design aid ang resulta. I-verify ito laban sa kasalukuyang standard.
Ano ang ginagawa ng motor calculator?
Iniuulat ng tool ang full load current, synchronous speed, shaft speed, full load torque at starting current ng induction motor. Gumagana ito mula sa shaft rating sa kilowatts, sa voltage, bilang ng phase, bilang ng pole, at slip.
Aling mga input ang pinakamahalaga?
Itinatakda ng shaft rating at ng voltage ang current. Parehong nagpapataas ng current ang power factor at efficiency para sa parehong shaft rating. Itinatakda ng bilang ng pole at ng supply frequency ang synchronous speed. Itinatakda ng slip percent kung gaano kababa ang shaft speed kumpara dito.
Paano kinakalkula ang starting current?
Ipinapalagay ng tool ang direct on line start sa anim na beses ng full load current ng motor. Sinasabi nito iyon sa note sa bawat resulta. Ang soft starter, star delta starter o variable speed drive ay nagbibigay ng ibang starting current. Gamitin ang nameplate figure kapag mayroon ka nito.
Puwede ko bang gamitin ang resulta para i-size ang cable?
Gamitin ang full load current bilang design current sa cable size tool. Nakakaapekto rin ang motor starting sa voltage drop at sa pagpili ng protective device, at hindi ito sinusuri ng tool na ito. Nasa page address ang mga input, kaya muling nagagawa ng link ang resulta.
Mga worked example
- Dairy shed motor current: 15 kW at 400 VFull load current, shaft speed, torque and DOL starting current for a 15 kW 400 V dairy shed vacuum pump motor, worked through the AmpSize motor engine.
- What size generator for a dairy shedSize a standby set for a dairy shed from its load list. The vacuum pump's start sets the size, then staggered steps, a drive and a soft starter shrink it.
- Motor starting current for a 55 kW DOL startFull load current, DOL starting current, shaft speed and torque for a 55 kW four pole motor at 400 V, and what a soft starter or a VSD changes.
- Starting a loaded conveyorA 22 kW conveyor that needs 120 % torque to break away. Why star-delta and a soft starter will not start it, and what a drive or autotransformer does.
- Motor circuit for a 15 kW pump: DOL or star-deltaSize a 15 kW 400 V pump circuit: cable, breaker, contactor and overload relay. Compare DOL, star-delta, soft starter and drive starts.
- Motor full load current: 11 kW 400 V DOLFull load current, shaft speed, torque and direct on line starting current for an 11 kW four‑pole 400 V induction motor, with the figures the tool returns.
Background
- Generator sizing for motor startingWhy a motor's start, not its running load, often sets a generator's size. Running and starting kVA, voltage dip, starting methods and derating.
- Motor circuits and startingHow full load current sizes the cable and starting current sizes the device on a motor circuit, with a worked 22 kW 400 V motor and the cable the tool selects.
- Motor starters, contactors and overload relaysHow to choose a motor starter: locked-rotor current, star-delta, soft starters, AC-3 and AC-23 duty, the overload relay and when motor protection applies.
- Motor starting methods: current and torqueWhy a cage motor draws six or seven times full load current at start, and how star-delta, an autotransformer, a soft starter and a drive trade it for torque.
- Industrial switchboards: fault rating, form, IPWhat the three ratings on an industrial switchboard or motor control centre mean, how each one is chosen, and which AmpSize tools feed the numbers behind them.
Mga kaugnay na tool
- Cable size calculatorFind the smallest cable size that passes each check.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Full load current calculatorCalculate full load current from power, voltage and phase.Walang standard
- Three phase power calculatorConvert between power, current, voltage and power factor.Walang standard
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