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# multiple speed setting for an electric vehicle? Answered

suppose an Ev had to run on different speeds say 30 miles/hr and 40 miles/h and vice versa. So how will the the current and voltage changes according to this situation.
Say you have a 400w motor and torque is known already and is calculated according to the required acceleration.

In short if you have an Ev and u want to set the ev run on different speeds what are the quantities that have to be checked or monitored (current,voltage) and .If you move from 30 to 40 miles/h what will happen to the variables?

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## Comments

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In a PMDC motor output speed is proportional to applied voltage. There is no need for any deep calculation.

heii thanks
But what will happen if it exceeds the rated voltage of motor,IF a motor is specified as 24v 400w then 24 v is the voltage @ which it give fine performance.So I hope it's peak performance will be at that time only. By increasing the voltage in order to increase speed if it exceeds rated voltage i guess it may have consequences,and what about finding at what voltage will it reach from 30-40 miles/hr.

That's right, a motor delivers its RATED performance, but voltage is not the only critical parameter - you HAVE to know/measure current - since power = current x voltage and mechanical power= electrical power x efficiency.

So during the design stage you need to DECIDE what the maximum speed will be, and how much power it will take, and whether that needs a gear box.

Your best bet is to get an operating graph from the motor manufacturers.