12 volt motors
 

Hi,

As a complete novice in regards to electrical matters, maybe one of you guys
can help me with a question.

I have access to a higher hp motor than needed for a particular task and am
wondering - will it draw current relative to the load on the motor or will it
always draw more than the smaller motor independant of the task asked of it?

Regards,


Leigh

12 volt motors
 

746 watts = 1 HP.

That said, the bigger motor will have more turning mass and larger
bearings to handle the load. It will also have more drag on larger
commutator brushes and is harder to turn so has a little more loss
running than the smaller motor.

The larger turning mass will draw more power every time it has to
start, power to get this extra mass moving. So, it draws more current
to get it and the load moving than the smaller motor will. This isn't
a problem if it's turned on and left on, not switched on and off every
minute from, say, a pump with a pressure switch.

These reasons are why the larger motor will draw more current than the
smaller one. How much more is how the two motors are designed. The
larger motor will run a lot longer as it is lightly loaded.

All this is nonsense if the motors in question are series DC motors
also called "universal motors" because they will work on AC as well as
DC. Series motors are what are in your vacuum cleaner, blender, those
motors around the house that "wind up" to very high speed and vary
their speeds widely as the load changes. A large series motor will
turn MUCH faster than the proper series motor for a specific load.
This will wear out the large motor faster than the small one and
probably turn the load too fast, any way, "winding up" to impressive
RPMs. Series motors are NEVER operated with no load as they will
overspeed and can explode from the centrifugal forces in the armature.



On 19 Mar 2004 06:49:57 GMT, (LeighWelchAngel)
wrote:

Hi,

As a complete novice in regards to electrical matters, maybe one of you guys
can help me with a question.

I have access to a higher hp motor than needed for a particular task and am
wondering - will it draw current relative to the load on the motor or will it
always draw more than the smaller motor independant of the task asked of it?

Regards,


Leigh


Larry W4CSC
POWER is our friend!

12 volt motors
 

Both statements are true. But the idling current draw of the bigger
motor is nothing to worry about.

Brian Whatcott Altus OK

On 19 Mar 2004 06:49:57 GMT, (LeighWelchAngel)
wrote:

Hi,

As a complete novice in regards to electrical matters, maybe one of you guys
can help me with a question.

I have access to a higher hp motor than needed for a particular task and am
wondering - will it draw current relative to the load on the motor or will it
always draw more than the smaller motor independant of the task asked of it?

Regards,


Leigh

12 volt motors
 

LeighWelchAngel wrote:
Hi,

As a complete novice in regards to electrical matters, maybe one of you guys
can help me with a question.

I have access to a higher hp motor than needed for a particular task and am
wondering - will it draw current relative to the load on the motor or will it
always draw more than the smaller motor independant of the task asked of it?

Regards, Leigh

Depends on what 'other' motor you mean, and the job.

Why not reveal all the details, motor types (ie series, shunt,
permanent magnet types, actual rated voltages and power ratings,
rated rpms, etc) and the job?

Can we safely assume, since you say you are a neophyte, that both
are 12 volt DC motors? I don't mean to be difficult, but you have no
idea of the suppositions some amateurs make.

If they are close in size, it might not be true, but with much
larger and smaller engines, it will always be so.

A ten horse motor will always draw more than a one horse motor.

A five horse motor starting up or under a heavy load may draw more
than a ten horse motor if the ten horse moter is not loaded down
with heavy work, just idling along.

Terry K