What's is resistance? How can you minimize it in a DC motor?

Answer 1

First we must define resistivity, which is a property of the metal used to make a wire. The following values, each multiplied by 10^-8 ohm-meters, are for a temperature of 20-deg. C:
Alumunum: 2.417
Copper: 1.543
Gold: 2.051
Lead: 19.2
Silver: 1.467
Resistivity is a function of the drift velocity of atomic conduction electrons which move through the metal with speeds of a few centimeters per second. (An electric wave propagates down a wire at nearly the speed of light.) The symbol for resistivity is the Greek letter rho.

Resistance is the result of the dimensions of a wire made of a given material. Here l is the length of the wire (in meters) and A is the cross-section area (in meters^2).

The resistance (R, in ohms) of any wire can be easily calculated using R = rho ( l / a )

In practical terms, using standard gauge (AWG) copper wires we simply look up the resistance per foot and multiply by the length to get the wire's nominal resistance.

I have a hunch you're looking to do something exotic. When I was in high school I loved to race electric slot cars. I was enough of a fanatic that I tried rewinding my motors with silver wire. I used the same gauge, length, and number of turns as for a high performance copper wound armature, except I used silver wire. I got the silver wire from a jewler's supply store and insulated it by dipped the wire in diluted epoxy adhesive (twice). The experiment was fantastically successful and I won the city championship two years in a row. Unfortunately, I trusted a "friend" with my secret and he blabbed it to the race committee. Not only did they immediately outlaw silver rewinds but they retroactively disqualified me from all the races I had already won! I thought I was doing cutting-edge engineering but they called me a cheater and smeared my reputation with a really nasty article in my hometown newspaper. Of course, I never touched a slot car again and grew up to be a cynical old fart who hates any type of committee and all bureaucrats.

Hope you found the information useful and the story entertaining.........

Answer 2

Resistance is the opposition to current flow in a circuit.

To minimize resistance in a DC motor, there are three things you can do. Increase wire size, increase turns, and/or increase field strength or magnetism. Oh yeah, I forgot. Increase rotor size and number of poles. The standing still resistance might go higher, but when working it will drop. i.e. Exciting current will be high, but running current will decrease.

Answer 3

Resistance is the opposition to current flow. If you are trying to minimize it in a DC motor you have, don't monkey with it.
Resistance is controlled by the wiring and its arrangement.

Answer 4

You need an inverter. AC can be transformed, DC can't. In practice all medium (and even some high) power systems could go DC these days but for long distance transmission the DC revolution seems to take a little longer than predicted. Transmission line losses could, theoretically, be minimized by going DC, but in practice the cost seems to be too high for most scenarios. It is unlikely that local distribution goes DC anytime soon because too many appliances need AC voltage and the cost to re-model homes with mixed AC/DC networks or to install converters is just too high.

Answer 5

Resistance is the opposition to electron flow that is an intrinsic characteristic of all conductors.

It can be minimized by using larger wire or fewer turns, or both.


Doug

Answer 6

The amount of force or energy it takes to turn the motor over
by hand when their is no electricity. Only guessing on minimizing
resistance, keep the motor oiled up frequently and as clean as
possible.