# Motor rpm calculation formula ## Number of Poles (AC Motor) Calculator

### Solved Example

The below step by step solved example problem may helpful for users to understand how the input values are being used in number of poles calculations.
Example Problem
Find the number of poles to design an induction motor to attain the synchronous speed Ns = 1500 rpm, whose line frequency f = 100 Hz?
Solution
The given data
f = 100 Hz
Ns = 1500 rpm

Step by step calculation
Formula to find p = 120f/Ns
substitute the values in the above formula
= (120 x 100)/1500
p = 8

In the field of electrical engineering while designing an induction motor for certain synchronous speed, finding the number of poles is important. The above formula, step by step calculation & solved example problem may be useful for users to understand how the values are being used in the formula to find the number of poles, however, when it comes to online for quick calculations, this calculator helps the user to perform & verify such calculations as quick as possible.

Sours: https://ncalculators.com/electrical/induction-motor-poles-calculator.htm

Hello guys, welcome back to my blog. In this article, I will discuss how to calculate RPM of dc and ac motor, formula to calculate RPM of motor, what is RPM, why it’s important to calculate RPM, how to calculate the speed of the motor, etc.

If you have any doubts related to electrical, electronics, and computer science, then ask questions. You can also catch me on Instagram – Chetan Shidling.

How To Calculate RPM Of DC And AC Motor

When running, monitoring, servicing, or replacing a motor, it’s necessary to know its specifications. One important measurement is revolutions per minute, or RPM, which represents the speed of a motor. In this guide, we’ll explain how to calculate the RPM of a motor and why it’s so necessary.

What Is the RPM of a Motor?

RPM is a measurement utilized to represent a motor’s speed. It stands for revolutions per minute and represents the rate at which the rotor is rotating, which is the number of times the rotor shaft makes a full rotation each minute. It can be done to measure the speed of motors, turbines, centrifuges, conveyors, and other devices.

Why It’s Important to Calculate RPM

Measuring motor RPM, as well as other quantities like torque, voltage, and power is necessary when choosing a motor for a given application. Calculating motor speed can help you pick the right kind of motor while replacing components and help you get better repair decisions. You also require to know RPM to control and monitor motor operation efficiently.

How to Calculate AC Motor RPM

To determine RPM for an AC induction motor, you multiply the frequency in Hertz (Hz) by 60 — for the number of seconds in a minute — by two for the negative and positive pulses in a cycle. Yourself then divide by the number of poles the motor has:

• (Hz x 60 x 2) / number of poles = no-load RPM

AC Motor RPM Calculation Examples

Let’s take a look at some cases. For an AC motor, the number of poles and the frequency determine the no-load RPM. For a 60 Hz system with four poles, the calculations to discover RPM would be:

• (Hz x 60 x 2) / number of poles = no-load RPM
• (60 x 60 x 2) / 4
• 7,200 / 4 = 1,800 RPM

How to Calculate DC Motor RPM

The emf equation of DC motor is given by

Here, N = speed of rotation in rpm. P = number of poles. A = number of parallel paths. Z = total no. conductors in the armature.

This was about how to calculate RPM of dc and ac motor. I hope this article ” How To Calculate RPM Of DC And AC Motor ” may help you all a lot. Thank you for reading.

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Chetan Shidling

I am a learning enthusiast, blogger, YouTuber, digital marketer, freelancer, and content creator. I always like to share my knowledge through blogging, Instagram, and youtube.

Sours: https://www.cselectricalandelectronics.com/how-to-calculate-rpm-of-dc-and-ac-motor-formula-to-calculate-rpm/

## How do I calculate the RPM's of a stepping motor?

Formula for calculating stepping motor speed.

Below is the RPM formula for steppering motor drives that use pulse signals to create motion.
RPM = a/360 * fz * 60

RPM = Revolutions per minute.
“a” = step angle
“fz” = pulse frequency in hertz

Example 1:  Drive step resolution is set for 1000 steps per revolution.
Find step angle: 360 (degrees of rotation) divided by 1000 (steps per revolution) = .36 (degrees of rotation per step)
With input frequency of 1000hz, .36 / 360 * 1000 * 60 = 60 rpm
Example 2: Drive step resolution is set for 500 steps per revolution.
Find step angle: 360 (degrees of rotation) divided by 500 (steps per revolution) = .72 (degrees of rotation per step)

With input frequency of 1000hz, .72 / 360 * 1000 * 60 = 120 rpm.

To find required frequency to meet desired speed we must find Fz:
RPM / ( (a/360) * 60) = Fz

Step 1. Divide step angle by 360:  .36/360 = .001,  then multiply by 60 (seconds) .001 * 60 = .06
Step 2. Divide desired speed by .06: Desired speed of 500 rpm’s.   Therefore ; 500 / .06 = 8333.33   ( 8333.33 is the frequency in hertz required to reach 500 rpm’s for drive set at 1000 steps per revolution)

Rev 1-7-20

FA337686  |  07-Jan-2020

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## What Determines the Rotating Speed of a Motor?

Electric motors are characterized by their variety and wide range of sizes. There are fractional horsepower (hp) motors for small appliances, and motors with thousands of hp for heavy industrial use. Other specifications found in motor nameplates include their input voltage, rated current, energy efficiency and speed in RPM.

The rotating speed of an electric motor depends on two factors: its physical construction, and the frequency (Hz) of the voltage supply. Electrical engineers select the speed of a motor based on the needs of each application, similar to how the mechanical load determines the horsepower required.

### Make sure your building has the right electric motor for each application. ### How the Voltage Frequency Relates to Motor Speed

Depending on the country, the power supply will have a frequency of 60 Hz or 50 Hz. Although a three-phase motor will rotate with both power inputs, there will be performance issues if a motor is specified for one frequency and used with the other. Since a 60Hz voltage supply switches polarity 20% faster than a 50Hz supply, a motor rated for 50Hz will spin at 20% higher rpm. Motor torque stays relatively constant, and a higher speed results in a higher shaft power. The motor also releases more heat, but the cooling fan also speeds up with the shaft, helping remove the extra heat. The motor also tends to draw more reactive current, which reduces its power factor.

Connecting a 60Hz motor to a 50Hz power supply is a more delicate matter. Reducing speed at the same voltage can saturate the magnetic core of the motor, increasing current and overheating the unit. The simplest way to prevent saturation is by lowering the input voltage, and ideally the V/Hz ratio should stay constant:

• A 60Hz motor operating at 50Hz is at 83.3% of its rated frequency.
• To keep the V/Hz ratio constant, the input voltage should also be reduced to 83.3%.
• If the electric motor normally operates at 240V and 60Hz, the input voltage at 50Hz should be 200V to keep a ratio of 4 V/Hz.

### Motor Wiring and Number of Poles A permanent magnet has two poles, but motors can be wired so their magnetic field has a higher number of poles. A two-pole motor completes a full revolution with one polarity change, while a four-pole motor only rotates 180° with one polarity switch. More poles result in a lower motor speed: if all other factors are equal, a 4-pole motor will rotate at half the speed of a 2-pole motor.

• A 60 Hz power supply changes polarity 60 times per second, and a two-pole motor will spin at 3,600 rpm when connected to this source. A four-pole motor will only rotate at 1,800 rpm.
• For 50 Hz motors, the speed is 3,000 rpm with 2 poles, and 1,500 rpm with 4 poles.

The concept can be summarized with the following equation: Using this equation, a 4-pole motor at 60Hz has a speed of 1,800 rpm, while a 6-pole motor at 50Hz has a speed of 1,000 rpm. However, this is actually the speed of the magnetic field, called the synchronous speed, which is not always equal to the shaft speed.

• In a synchronous motor, the rotor uses a permanent magnet or electromagnet to rotate at the calculated speed.
• On the other hand, an induction motor will operate slightly below the calculated rpm. This is how electromagnetic induction works, and should not be viewed as a malfunction.

If an electric motor has a nameplate speed of 1,800 rpm, one can conclude that the unit is a 4-pole synchronous motor rated for 60 Hz. On the other hand, if the nameplate speed has a lower value like 1,760 rpm, the unit is an induction motor.

A variable frequency drive can control motor speed by adjusting the input frequency, as its name implies. A VFD can also modulate voltage to keep the V/Hz ratio below the point where the magnetic core is saturated. Thanks to this feature, a VFD does not damage a motor even when speed is reduced below the nameplate value. The main drawback of VFDs is causing harmonic distortion, since they are nonlinear loads, but this can be compensated with harmonic filters.

Sours: https://www.ny-engineers.com/blog/what-determines-the-rotating-speed-of-a-motor

## AC Induction Motor Slip Calculator

### Solved Example

The below step by step solved example problem may helpful for users to understand how the input values are being used in slip percentage calculations.
Example Problem
Find the slip of an induction motor, whose actual speed n = 1450 rpm & synchronous speed ns = 1500 rpm.
Solution
The given data
n = 1450 rpm
ns = 1500 rpm

Step by step calculation
Formula to find speed difference = ns - n
Formula to find slip = (ns - n) x 100/ns
substitute the values in the above formulas
speed difference = 1500 - 1450
= 50

slip = 50/1500 x 100
slip = 3.33%

In the field of electrical engineering while designing an AC induction motor, calculating the slip is much important. The above formula, step by step calculation & solved example problem may be useful for users to understand how the values are being used in the formula to find the slip difference & percentage, however, when it comes to online for quick calculations, this calculator helps the user to perform & verify such calculations as quick as possible.

Sours: https://ncalculators.com/electrical/induction-motor-slip-calculator.htm
Calculating RTU airflow

## How to Calculate the RPM of a Motor and Speed Reducer

Motors run at a specific revolutions per minute (RPM) and a speed reducer is needed if you want to keep that motor, but have a lower RPM. Calculating the RPM resulting from a motor and speed reducer assembly requires only basic mathematical knowledge.

Write down the rated RPM of your motor; for example, 5000 RPM.

Write down the ratio of the speed reducer; for example, 12:5.

Calculate the reduction by dividing 12 by 5, which equals 2.4.

The RPM of the assembly is the RPM motor divided by the reduction. In our example, it would be 5000 RPM/2.4 = 2083 RPM.

### Items you will need

• Motor base RPM

• Speed reducer ratio

#### Tips

The ratio of a reducer will always be in the form of A:B, where A>B.

#### Warnings

The RPM found should always be lower than the base RPM of the motor. If it is not, either redo your calculation or make sure you did not get a speed multiplier instead of a reducer.

References

Tips

• The ratio of a reducer will always be in the form of A:B, where A>B.

Things You'll Need

• Motor base RPM
• Speed reducer ratio

Warnings

• The RPM found should always be lower than the base RPM of the motor. If it is not, either redo your calculation or make sure you did not get a speed multiplier instead of a reducer.

Writer Bio

Andrea Helaine has a Bachelor of Philosophy in theology and is currently finishing her thesis course for a Master of Fine Arts in creative writing. Helaine has been writing professionally for over 10 years and has been published in several anthologies and is currently breaking into the screenwriting market.

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Sours: https://itstillruns.com/calculate-rpm-motor-speed-reducer-7699356.html

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