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# What will be the DC Motor Speed at 50Watt?

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#### nkarnani

##### Newbie level 5
I am using a 24V 200AH battery to run for 7hrs.

Inorder to do that i can use only 285 Load.

I have to run 4 modules using this power so 285/4=71.25 W for each module.

Now each module consist of one DC motor which can be allowed to eat 50 Watt.

So, can any one tell me the Speed and Current of the motor for 50Watt looking @ the Power,Torque,Speed and Character characterstics?

Assume that the torque is around 1N-m.

Power,Torque,Speed and Character characterstics

How are you going to limit the current/power into the motor? If you apply 24 Volts, and put a load of 1 N-M on it, it's going to WANT to draw about 20 A; that's 480W, not 50W.

nkarnani

### nkarnani

Points: 2
To reduce the motor power you will need to reduce to voltage applied to the motor, such as by using PWM. The voltage needed to reduce the power is not readily obtained from the graph you show. You would need a graph of torque/power versus applied voltage to determine that.

nkarnani

### nkarnani

Points: 2
How are you going to limit the current/power into the motor? If you apply 24 Volts, and put a load of 1 N-M on it, it's going to WANT to draw about 20 A; that's 480W, not 50W.

To reduce the motor power you will need to reduce to voltage applied to the motor, such as by using PWM. The voltage needed to reduce the power is not readily obtained from the graph you show. You would need a graph of torque/power versus applied voltage to determine that.

Lets say i am using PWM to control motor speed..
Thing is i am using 4 motors and putting 300kg on the vehicle.
So, it puts 75kg load to each motor.
I am not quite aware of how convert this 70kg into N-m??

for 7hrs i m allowed to use only 50 Watt per motor..

1) Will it be possible to run at certain speed?

2)If Possible, What will be that Speed?

The weigh has no direct simple relationship to the torque. You can only determine the torque (N-m) required by determining the friction to move the vehicle with the 300kg weight, how fast you want to accelerate the vehicle, and how steep an incline you want to climb.

The weigh has no direct simple relationship to the torque. You can only determine the torque (N-m) required by determining the friction to move the vehicle with the 300kg weight, how fast you want to accelerate the vehicle, and how steep an incline you want to climb.

I am running the vehicle on a plain surface.

the thing is that i want a 7hr backup from the battery speed is not the issue..

Can you tell @ what speed i can get 7hr constant running from 24V 200AH battery

Still not enough info. Need to know the friction of the vehicle when running on the plain surface (how much force will it take to move the vehicle at a steady speed) and the diameter of the drive wheel. At higher speeds you will need to include air resistance. Only then can you determine the required torque. You will likely need to do some measurements. Understand?

nkarnani

### nkarnani

Points: 2
Still not enough info. Need to know the friction of the vehicle when running on the plain surface (how much force will it take to move the vehicle at a steady speed) and the diameter of the drive wheel. At higher speeds you will need to include air resistance. Only then can you determine the required torque. You will likely need to do some measurements. Understand?

Ok Thanx man for being with me..

So, here is what i have calculated
i have 75 kg weight at each motor
so Force
F=mg=75*9.8= 735 N
and the diameter of wheel is 16 inch

so torque

T=F*r= 735 N * 8 inch =150 N-m

Now, lets not consider air resistance friction in it.

So, how much RPM I will be able to get if i apply 50 watt to the motor?

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