电动机计算器
求出电动机的满载电流、启动电流和转矩。
尝试一个工程 6
每项工作都会预填示例数值。请替换为您自己的数值。
- 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.
输入
使用默认输入值的示例计算。
- 轴功率
- 15 kW
- 相
- 三相
- 电压
- 400 V
- 功率因数
- 0.85
- 效率
- 0.9
- 极数
- 4
- 频率
- 50 Hz
- 转差率
- 3 %
满载电流
28.3A
- 启动电流，DOL
- 169.81A
- 同步转速
- 1,500rpm
- 轴转速
- 1,455rpm
- 满载转矩
- 98.45Nm
此结果仅供设计参考。请对照现行标准进行核验。
计算步骤
- 满载电流结果28.3A
- 同步转速1,500rpm
- 轴转速1,455rpm
- 满载转矩98.45Nm
- 启动电流169.81A
关于此计算器
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.
问题
结果仅供设计参考。请依据现行标准核对。
电动机计算器有什么作用？
工具报告感应电动机的满载电流、同步转速、轴转速、满载转矩和启动电流。它以千瓦轴功率、电压、相数、极数和转差率为输入。
哪些输入最重要？
轴功率和电压决定电流。对于相同的轴功率，功率因数和效率都会增大电流。极数和供电频率决定同步转速。转差率百分比决定轴转速低于同步转速的程度。
启动电流如何计算？
工具假定直接启动，启动电流为电动机满载电流的六倍。每个结果中都会以注释说明这一假定。软启动器、星-三角启动器或变频器给出的启动电流不同。如有铭牌数值，请使用铭牌数值。
可以用结果来选择电缆截面吗？
在电缆截面工具中，将满载电流作为设计电流。电动机启动也会影响电压降和保护装置的选择，但本工具不检查这些内容。输入值保存在页面地址中，因此链接可复现结果。
计算示例
- 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.
背景
- 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.
相关工具
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