DC motor current spike

[[email protected]]

i'm running a .5 hp 12v dc motor. it works fine until i put a load on
it. with the load i am using, the initial current spike exceeds the
rating of my power supply so the power supply shorts. my power supply
is rated for 52a surge, 40a constant. is there a device or some sort
of circuit that i could utilize to solve this problem?

 

[Paul Hovnanian P.E.]

i'm running a .5 hp 12v dc motor. it works fine until i put a load on
it. with the load i am using, the initial current spike exceeds the
rating of my power supply so the power supply shorts. my power supply
is rated for 52a surge, 40a constant. is there a device or some sort
of circuit that i could utilize to solve this problem?

It would depend on the characteristics of the load and load application.
Also, what kind of DC motor is it (series, shunt, etc.). What is the
time duration for that power supply 52A surge rating?

Typically, the worst case inrush current will be the locked rotor level
experienced when the motor starts. However, if it starts unloaded, the
motor will accelerate rapidly and the current will decrease with
increasing motor speed. It seems that your power supply is capable of
providing this current-time envelope successfully. However, the load
inertia is such that it exceeds this, which the power supply treats as
an overload.

 

[Tim Wescott]

i'm running a .5 hp 12v dc motor. it works fine until i put a load on
it. with the load i am using, the initial current spike exceeds the
rating of my power supply so the power supply shorts. my power supply
is rated for 52a surge, 40a constant. is there a device or some sort
of circuit that i could utilize to solve this problem?

The best thing to do is to use a power supply or amplifier that will
current limit gracefully. This may make the motor take longer to
recover from a load change, but it'll keep your power supply happy.

Are you driving the motor with an amplifier, or just a switch? If
you're using an amplifier, you should be able to find one that'll
current limit.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

 

[Ban]

i'm running a .5 hp 12v dc motor. it works fine until i put a load on
it. with the load i am using, the initial current spike exceeds the
rating of my power supply so the power supply shorts.

It doesn't short, it shuts down

my power supply
is rated for 52a surge, 40a constant. is there a device or some sort
of circuit that i could utilize to solve this problem?

With full load yor motor will probably draw already more than your
continuous 40A rating, when stalled maybe 120A. just measure the DC
resistance and you will know. To supply such a current, your power
supply is not sufficient. The only possbility would be to connect a car
battery across the output and set your supply to 13.8V, to recharge the
battery.

 

[Boris Mohar]

i'm running a .5 hp 12v dc motor. it works fine until i put a load on
it. with the load i am using, the initial current spike exceeds the
rating of my power supply so the power supply shorts. my power supply
is rated for 52a surge, 40a constant. is there a device or some sort
of circuit that i could utilize to solve this problem?

Flywheel and or one of those Farad capacitors that they use in car audio.
Make sure that you power supply can charge such cap.



Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place

 

[w_tom]

An additional point to supplement your other good responses. The
"initial current spike exceeds the rating of my power supply" will
create problems if power supply is a foldback current limit type. With
excessive current, load must be removed so that foldback current
limited supply can recover.

 

[ehsjr]

i'm running a .5 hp 12v dc motor. it works fine until i put a load on
it. with the load i am using, the initial current spike exceeds the
rating of my power supply so the power supply shorts. my power supply
is rated for 52a surge, 40a constant. is there a device or some sort
of circuit that i could utilize to solve this problem?

I don't think it's a spike. I think what you have
is a simple overload - at start up, the motor draws more
current than the supply can provide. I'll bet the LRA
exceeds the power supply capability.

So it seems your first step has to be to determine the
LRA rating of your motor. If it exceeds the supply
rating, you'll need to increase the supply or decrease
the load on the motor at startup. Or maybe "kick start"
the motor with a battery, then switch in the supply
to handle the continuous run and to recharge the battery.

Ed