Calculating Current in DC Motor at 11V, 2000 RPM

AI Thread Summary
To calculate the current drawn by a 12V permanent magnet DC motor operating at 11V and 2000 RPM, the stall current is given as 2 amperes, allowing the resistance to be determined as 6 ohms. The back electromotive force (e.m.f) is proportional to the motor's speed, which can be expressed in relation to the maximum speed and voltage. By applying the relationship between speed, voltage, and current, the current at the specified conditions can be calculated. The resistance value is crucial for determining the current since it influences the back e.m.f. Thus, the current can be accurately calculated using the derived resistance and the motor's operational parameters.
farry1024
Messages
2
Reaction score
0
Question:
Assume that a 12V permanent magnet DC motor is to be used for moving the robot legs.
It has a stall current of 2 ampere and a no load speed of 3000 r.p.m.
Assumer that the friction at no load spped was so little that it can be neglected .
When the suply is at 11V, the motor is moving the legs at its rated speed of 2000 rom due to firction, what current would it draw?

I try to answer:
Vmax = 12V
Imax = 12A
ωmax = 3000 rpm <<<ω=omoega, i.e. rotational speed

V1 = 11V
I1 = unknown
ω1 = 2000 rpm

back e.m.f proportional to ω

ω1/ ωmax = back e.m.f 1 / back e.m.f max
and back e.m.f = V- Ir

ω1/ ωmax = [ V1 - I1 ( r ) ] / [ Vmax - I max (r)]

However, I find that I do not have the resistance, how can I calculate? thanks.
 
Physics news on Phys.org
You know that the stall current is 2 amperes, and when the motor is stalled there is no back emf. So the resistance is 12 V/2 A = 6 ohms.
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Calculating Armature Torque for 250V DC Motor
Replies
13
Views
3K
DC motor. Calculate the current
Replies
1
Views
2K
What is the best DC motor for spinning a vortex impeller at 3000 rpm?
Replies
2
Views
2K
Calculating Required Torque for 12V DC Motor
Replies
17
Views
4K
Questions about DC motor drive calculations
Replies
3
Views
2K
What Is Back EMF in DC Motors and How Does It Affect Performance?
Replies
3
Views
3K
Simple DC motors Current, Torque, EMF and Faraday's Law
Replies
14
Views
8K
Engineering How Do You Calculate Armature Current and Efficiency in a DC Shunt Motor?
Replies
8
Views
7K
Using a DC Motor as a Generator
Replies
12
Views
8K
Engineering How Does Armature Voltage Affect the Speed of a Separately Excited DC Motor?
Replies
3
Views
2K

Hot Threads

Recent Insights

Back
Top