# Two electricity questions about KVL and a pole numbers

• TheNaturalStep
In summary, the conversation is discussing the concept of KVL (Kirchhoff's Voltage Law) and its application to a circuit with a current source. The formula ns=120*f/p is mentioned, with f representing frequency and p representing the number of poles. The speaker is unsure of how to determine the number of poles in an engine and explains that their old teacher did not provide an explanation. They clarify that the 120 in the formula is related to magnetic poles in a motor drive. The conversation then shifts to discussing the options for the number of poles (2, 4, 6, 8, etc.) and how to determine the correct value. It is also mentioned that the conversation is not referring to poles in the
TheNaturalStep
What happens when you do a KVL through and current source?

A formula I can not understand

ns=120*f/p

f=frequency P=number of poles …..

How shall you know how many poles you got?, my old teacher just wrote it down as it would be obvious. But I think ti is related to what kind of engine you got …

Kindly TNS

LOL. You really had me going there for a moment. I thought you were referring to poles in the complex plane for the circuit polynomial transfer function.

You are referring to magnetic poles in a motor drive instead. That's where the 120 comes from (at least in the US -- it would be 100 in Europe). What current source are you referring to in your KVL? Are you trying to write a KVL around all the loops in a motor?

1 No i just wonder how i shall i do an KVL when i ahve an current source.

2 about the polles they say they can be

P= 2 4 6 8 ... but i don't know how you know which ...

## What is Kirchhoff's Voltage Law (KVL)?

Kirchhoff's Voltage Law states that the algebraic sum of voltages around a closed loop in a circuit must equal zero. In other words, the sum of voltage drops must equal the sum of voltage rises.

## How do I apply KVL to a circuit?

To apply KVL to a circuit, choose a direction for the loop and assign a polarity (positive or negative) to each voltage source and component. Then, starting at any point in the loop, use Ohm's Law (V=IR) to calculate the voltage drop across each component. The sum of the voltage drops should equal the sum of the voltage rises.

## What is the relationship between pole numbers and voltage in a motor?

The number of poles in a motor refers to the number of electromagnets in the stator. The more poles a motor has, the higher the voltage required to power it. This is because the voltage must be high enough to overcome the back EMF (electromotive force) generated by the motor's magnetic field.

## How do I calculate the number of poles in a motor?

The number of poles in a motor can be calculated by dividing the synchronous speed (speed at which a motor's rotor turns) by the frequency of the power supply. The result is then divided by 120 to get the number of poles.

## What is the purpose of calculating the number of poles in a motor?

Calculating the number of poles in a motor is important for determining the motor's speed and power requirements. It also allows for proper matching of the motor to the power supply, ensuring efficient operation and preventing damage to the motor.

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