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When using a step-down transformer (120vac-18vdc), will I need to limit the current going to the motor? Answered

Attempting to modify an old rechargeable battery for power tools into a power source that can be plugged into the wall and inserted into the power tool.

I know that step down transformers raise the current, but I am unsure if this will be an issue. Either way...

What is the best way to reduce current while not reducing voltage? Is that possible?

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user
-max- (author)2014-12-24

Many appliances if you run them at their rated voltage, they will draw the current that they need. You can control the amount of current in one of 2 ways, by decreasing or increasing the load impedance (so electricity can flow easier or less easily respectfully) or by raising or lowering the voltage (to force more electrons though a load or less force respectfully).

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iceng (author)-max-2014-12-24

I have never hear-of, seen or felt "RESPECTFUL L" electricity in my life time !

BTW electrons forced or cajoled through a load is usually called Current Flow.

In fact there is a very good analogy in water to electricity.

Water pressure is like Voltage.

Current flow is like Current flow.

Restricted piping is like Resistance.

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user
-max- (author)iceng2014-12-24

Where did I say " 'RESPECTFUL L' " I understand how electricity works and how it is analogous to water piping. I simple described how certain changes in voltage or impedance (resistance only applies to certain cases, it has a more specific definition in my understanding) will result in a change in current. (higher or lower voltages will result in higher or lower currents respecfully.)

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iceng (author)-max-2014-12-24

RESPECTFUL with a space & L typo..

Quote "easily respectfully)" and "currents respectfully." with a mere change of the "y"

Im happy, you understand how electricity works and how it is analogous to water piping but it is not electricity that is respectful or has a need to be nearly as much as you need to be very respectful of electricity.

Anyway the whole idea of respectful electricity just put me off.

Other then that you are correct, the load will use what current it is designed for and YES voltage changes cause current changes in proportion to the voltage changes !

What is your problem anyway ;-)

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user
iceng (author)2014-12-17

In actual fact when you spin that motor faster then it was running under the DC (called overhauling), a marvelous event will occur, the motor will use negative energy !!!

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user
steveastrouk (author)2014-12-17

No need. DC motors pull the current they need.

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