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A synchronous motor will spin at the system frequency. 60 Hz translates into 60*60 = 3600 direction changes per minute. If this is a two pole motor (one north and one south), it will spin 1 rotation per direction change. If it is a four pole motor (two north and two south), it will spin 1/2 rotation per direction change.

If this is an induction motor, it will spin at a frequency slightly less than an equivalent synchronous motor; this frequency difference is referred to as slip.

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Q: How do you calculate the rpm of a motor with a known number of poles and a frequency of 60 Hrtz?
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How does an ac drive variable speed drive operate to control speed?

Answer #1 It varies the frequency fed to a synchronous AC motor. As the frequency changes, so does the motor speed. Answer #2 The formula for calculating speed is: (120 X motor supply frequency) / number of poles 120 is a fixed number, so is the number of poles for a given motor, hence the only variable is the motor supply frequency. AC drives vary the motor supply frequency in turn achieving speed control.


How do you check number of poles on a three phase induction motor?

Name plate data should indicate the number of poles / RPM. For speed N= (120 x Frequency) / Number of poles Using this formula you can find out the number of poles, provided you have other parameters available. If no data is available, run the motor on no load, and measure the rpm, know the frequency, calculate the poles.


How is The RPM of an electric motor is determined?

The two main factors are the frequency and the number of poles of the motor. A formula for RPM is HZ x 60 x 2/ number of poles the motor has.


How speed of a squirrel cage induction motor can be varied?

There are two ways of changing the speed of AC motors,by altering the frequency or the number of poles in the motor. An increase in frequency of the supply voltage to the motor will cause it's speed to increase while reducing the frequency will causes the motor speed to drop. This is the method exploited by Variable Speed/Frequency Drive. The second method of changing the number of motor's stator poles is the difficult. The manufacture must design the motor such that the number of the motor's pole in operation can be increased or reduced. Increasing the number of poles increases the stator flux density which decreases the speed. Decreasing the number of poles does the opposite. This method is typically found in two speed motors and it's rarely used compared to VSDs.


What is the rotor speed of synchronous motor?

It depends on the number of poles and the frequency of the power. A two pole motor running on 60 Hz would rotate at 1800 RPM.

Related questions

How does an ac drive variable speed drive operate to control speed?

Answer #1 It varies the frequency fed to a synchronous AC motor. As the frequency changes, so does the motor speed. Answer #2 The formula for calculating speed is: (120 X motor supply frequency) / number of poles 120 is a fixed number, so is the number of poles for a given motor, hence the only variable is the motor supply frequency. AC drives vary the motor supply frequency in turn achieving speed control.


How do you check number of poles on a three phase induction motor?

Name plate data should indicate the number of poles / RPM. For speed N= (120 x Frequency) / Number of poles Using this formula you can find out the number of poles, provided you have other parameters available. If no data is available, run the motor on no load, and measure the rpm, know the frequency, calculate the poles.


How is The RPM of an electric motor is determined?

The two main factors are the frequency and the number of poles of the motor. A formula for RPM is HZ x 60 x 2/ number of poles the motor has.


How speed of a squirrel cage induction motor can be varied?

There are two ways of changing the speed of AC motors,by altering the frequency or the number of poles in the motor. An increase in frequency of the supply voltage to the motor will cause it's speed to increase while reducing the frequency will causes the motor speed to drop. This is the method exploited by Variable Speed/Frequency Drive. The second method of changing the number of motor's stator poles is the difficult. The manufacture must design the motor such that the number of the motor's pole in operation can be increased or reduced. Increasing the number of poles increases the stator flux density which decreases the speed. Decreasing the number of poles does the opposite. This method is typically found in two speed motors and it's rarely used compared to VSDs.


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There is software that can be downloaded to help calculate the number of turns for a three phase motor. There are also diagrams which can be found for the most frequently used calculations.


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How do you change the direction of rotation of synchronous motor?

A synchronous motor aways runs at the synchronous speed, which is the supply frequency divided by the number of pairs of poles in the motor. For a 4-pole motor the speed is 1500 rpm (50 Hz supply) or 1800 rpm (60 Hz supply). The mechanical phase of the rotor is liable to be a little unstable under changing load conditions.


Can the rpm on a sears 1 hp electric motor be changed?

yes, you can. in A/C motor rps(rev/sec) is N(rps)= f/p where f is the frequency and p is the number of pair poles. By increasing or decreasing the frequency the rps will change accordingly. By having less or more pair poles the rps will be increased or reduced. the more pair poles the lower will be the rps.


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A normal motor run at a fixed speed depending on: AC motors: Voltage and frequency (Hetz) and number of poles DC Motors: Armature voltage Stepper motors speed depend on the drive pulse frequency.


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