Tātaitai mōtā
Kimihia te iahiko uta katoa mōtā, te iahiko tīmata me te torque.
Whakamātau mahi 6
Ka whakakī ia mahi i ngā uara tauira. Whakakapia ērā ki ō uara.
- 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.
Ngā whakauru
He tauira mahi me ngā whakauru taunoa.
- Pūngao tahanga
- 15 kW
- Ngā wāhanga
- Wāhanga toru
- Voltage
- 400 V
- Power factor
- 0.85
- Pai
- 0.9
- Ngā pou
- 4
- Auautanga
- 50 Hz
- Slip
- 3 %
Iahiko Uta Katoa
28.3A
- Au tīmata, DOL
- 169.81A
- Synchronous speed
- 1,500rpm
- Tere o te shaft
- 1,455rpm
- Torque utu katoa
- 98.45Nm
He āwhina hoahoa tēnei hua. Manatokohia ki te paerewa o nāianei.
Ngā hīkoi tātaitanga
- Au utanga katoaHua28.3A
- Tere tauritea1,500rpm
- Tere tahanga1,455rpm
- Hurihuri utanga katoa98.45Nm
- Au tīmata169.81A
Mō tēnei tātaitai
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.
Pātai
He āwhina hoahoa te hua. Manatokohia ki te paerewa o nāianei.
He aha te mahi a te tātaitai mōtā?
Ka whakaatu te taputapu i te Iahiko Uta Katoa, te synchronous speed, te shaft speed, te torque uta katoa me te iahiko tīmata o tētahi induction motor. Ka mahi mai i te shaft rating i ngā kilowatts, te voltage, te maha o ngā wāhanga, te maha o ngā pou me te slip.
Ko ēhea ngā uruhanga e tino nui ana?
Ko te reiti shaft me te voltage e whakatau ana i te iahiko. Ko te power factor me te efficiency e whakatairanga ana i te iahiko mō te reiti shaft ōrite. Ko te tatau pou me te auau puna hiko e whakatau ana i te synchronous speed. Ko te ōrau slip e whakatau ana i te tawhiti e heke ai te shaft speed i raro iho i tērā.
Me pēhea te tātai i te iahiko tīmata?
Ka whakaaro te taputapu ki te tīmata direct on line i te ono ōna iahiko uta katoa o te mōtā. Ka kī ia i roto i tētahi pitopito i ia putanga. He iahiko tīmata rerekē tā tētahi soft starter, tētahi star delta starter, tētahi variable speed drive rānei. Whakamahia te uara nameplate ina whai koe tētahi.
Ka taea te whakamahi i te hua hei whakarite i te rahi o tētahi taura?
Whakamahia te Iahiko Uta Katoa hei iahiko hoahoa i te taputapu Rahi Taura. Ka pā anō te tīmatanga mōtā ki te heke voltage me te kōwhiringa taputapu whakamaru, ā, kāore tēnei taputapu e tirotiro i ēnei. Ka noho ngā uruhanga ki te wāhitau o te whārangi, nō reira ka whakaatu tētahi hononga i te putanga.
Ngā tauira mahi
- 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.
Kōrero o muri
- 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.
Ngā taputapu hononga
- Tātaitai rahi tauraFind the smallest cable size that passes each check.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Tātaitai Iahiko Uta KatoaCalculate full load current from power, voltage and phase.Kāore he paerewa
- Tātaitai Power Wāhanga ToruConvert between power, current, voltage and power factor.Kāore he paerewa
He whai hua tēnei?
He pātai, he uara rānei e kitea ana he hē? Whakapā mai.