12VDC motor exceeding power supply on startup

[jamesdeen]

Hey everyone,
I'm using a 12V DC fan (car radiator fan) rated at 80W as a window fan, powering it with a 100W SMPS ( https://www.digikey.ca/product-search/en?x=23&y=16&lang=en&site=ca&KeyWords=1145-1070-ND+). About 50% of the time, the fan starts up fine. The other 50% of the time, the fan spins for about 1s and then stops, and restarts after 2s to try to turn on again.. this will cycle for as many as 10 times before the fan continuously runs.

I'm guessing that the fan is drawing more power at start and maybe putting the power supply into protection mode for 2s?

Is there anything simple I can do, such as add a capacitor to the output of the SMPS to help it handle the startup of the fan?

 

[D.A.(Tony)Stewart]

Yes the Fan start current will be higher and the hiccup mode will react.

A PWM soft start might work with a CMOS clock and logic level gate FET driver that has an RC control to go from 50 to 100% in a few seconds.

Another solution might be some other speed or current limit control during startup such as a delay relay and power R in series.

 

[Audioguru]

52 years ago I put a propeller on a motor I found and used it as a window fan. It sparked inside the motor.
Then "knock, knock" on the door. It was the RF cops and they said my neighbour complained about severe TV interference which was caused my fan motor. They said hundreds of people received my interference.
I apologized to my neighbours who complained then they bought me a new fan.

 

[dick_freebird]

An inrush current limiter circuit, to deal with the "locked rotor"
(inertial) current, is one option. Another might be to dig into the
SMPS and alter whatever soft-start time constant setting
component values there are, to ramp voltage slower. You might
also just poor-boy it with a multi-stage power switch that has
(say) a 2-ohm series resistor (to get going, slow, without tripping)
and 0 ohm paths (for full power running).