What factors affect the rotating speed of a motor?

In summary, the conversation was about the speed of motors and the equation used to calculate it. The equation applies to AC induction and some synchronous motors, but not to universal motors or DC brush commutated motors. The speed of an induction motor is dependent on the frequency of the power going to it, and tools that require speeds greater than 3600 rpm use universal motors or other methods such as frequency converters, gears, or pulleys.
  • #1
mainer0311
2
0
This is my first post, so I'll give a bit of an intro. I am an marine engineering cadet at mass maritime academy in my junior yet. I took physics II last semester and this semester I am taking electrical machines.

In class today we were talking about how fast motors can rotate and came up with this equation:

Ns = 120f/p Ns being the speed of the motor, f being the frequency and p being the number of poles.

with this equation using 60hz and a 2 pole motor it says that a motor will only rotate at 3600 rpm's.

I know this isn't true because wood working routers rotate well over 15,000 rpm.

I asked my Proff how this worked and was told to try and find an answer for next class.

I haven't been able to find anything searching google about it. Does anybody know how this works?


Thanks Cooper
 
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  • #2
Different types of motors have different speed and torque characteristics.
The equation applies to AC induction motors, which run asynchronously at just under that suggested. It also applies to some synchronous motors.
Universal motors, DC brush commutated motors and many others do not obey the equation.
 
  • #4
So the speed of an induction motor is dependent on the frequency of the power going to it?

And these tools that require speeds greater then 3600 rpm use a universal motor?

this is making more sense, thanks.
 
  • #5
Or a frequency converter. Or gears and pulleys. It all depends on the system being powered.
 

1. What is the rotating speed of a motor?

The rotating speed of a motor is the number of revolutions per minute (RPM) that the motor's output shaft makes. It is a measure of how fast the motor is rotating.

2. How do you measure the rotating speed of a motor?

The rotating speed of a motor can be measured using a tachometer, which is a device that measures rotational speed. It can also be calculated by dividing the number of revolutions made by the motor's output shaft in a given time period by the time period.

3. What factors affect the rotating speed of a motor?

The rotating speed of a motor can be affected by various factors such as the voltage and current supplied to the motor, the load on the motor, the type and design of the motor, and the efficiency of the motor.

4. How does the rotating speed of a motor impact its performance?

The rotating speed of a motor is directly related to its torque and power output. A higher rotating speed can result in a higher power output, while a lower rotating speed may result in a higher torque output. The rotating speed also affects the efficiency and lifespan of the motor.

5. Can the rotating speed of a motor be controlled?

Yes, the rotating speed of a motor can be controlled by adjusting the voltage and current supplied to the motor, using speed control devices, or by changing the design of the motor. This allows for precise control of the motor's performance and can be useful in various applications.

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