Researching Torque, Current and Flux Density

[monkeyhead]

Homework Statement

For this question you must research, to help you with working out your answer
a) A dc motor develops a torque of 600Nm when its armature carries a current of 30 Amperes. Predict the torque that will be developed when a 12% increase in flux density has taken place and the armaure current is increased to 35 amperes.

The Attempt at a Solution

I have to admit, I'm pretty stumped for this one! I have no clue on what formula links torque,current and flux density together what so ever. I'd imagine that there must be some sort of formula linking all those together right?
I'm not asking for someone to solve this for me but I would gladly appreciate a push in the right direction into where I should be looking! Any suggestions much appreciated
Many thanks
Matt

 

[Hootenanny]

A good place to start for your research would be with http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motdc.html#c1" .

 

[m2003]

Hi Matt,

I can definitely help you out with this question. Let's start by breaking down the problem and looking at the variables involved.

First, we have torque, which is a measure of rotational force. It is represented by the symbol "T" and is measured in units of Newton-meters (Nm).

Next, we have current, which is the flow of electric charge. It is represented by the symbol "I" and is measured in units of Amperes (A).

Lastly, we have flux density, which is a measure of the strength of a magnetic field. It is represented by the symbol "B" and is measured in units of Tesla (T).

Now, let's take a look at the relationship between these variables. According to the equation for torque in a DC motor, the torque (T) is equal to the product of the magnetic field strength (B) and the current (I), multiplied by the radius of the motor's armature (r). This can be represented as: T = B*I*r.

Therefore, if we want to predict the new torque (T') after a 12% increase in flux density (B'), and an increase in the current to 35 Amperes (I'), we can use the following equation:

T' = B' * I' * r

We already know that the original torque (T) was 600 Nm and the original current (I) was 30 Amperes. So, let's plug these values into the equation and solve for B' (flux density after the 12% increase):

600 Nm = B' * 30 A * r

B' = 600 Nm / (30 A * r)

B' = 20 Nm/A*r

Now, we can use this value for B' in our original equation to find the new torque (T'):

T' = (20 Nm/A*r) * 35 A * r

T' = 700 Nm

Therefore, the predicted torque after the 12% increase in flux density and an increase in current to 35 Amperes is 700 Nm.

I hope this helps to clarify the relationship between torque, current, and flux density and how to use it in a problem like this. Good luck with your research!