Solving Motor Stall Current Issue: Tips and Tricks | Master Project Update

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SUMMARY

The discussion focuses on addressing a stall current issue in a DC motor setup linked to a PMA wind turbine generator. The user initially selected a power supply unit (PSU) rated at 24V and 25A, which is insufficient for the motor's stall current, leading to PSU failure upon startup. Solutions proposed include using a 1-ohm series resistor rated at 600 watts or employing multiple 24V 100W truck headlamp globes in parallel to limit the startup current. Additionally, a switching current limiter is suggested as an alternative solution.

PREREQUISITES
  • Understanding of DC motor specifications and operation
  • Familiarity with power supply unit (PSU) ratings and limitations
  • Knowledge of electrical components such as resistors and light bulbs
  • Basic circuit design principles for implementing current limiting solutions
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  • Research the stall current characteristics of the OMPMDC34-18-24V-56C motor
  • Learn about designing and implementing a switching current limiter circuit
  • Investigate the use of resistors and their power ratings in motor applications
  • Explore alternative methods for managing inrush current in DC motors
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Electrical engineers, hobbyists working on motor control projects, and anyone involved in designing or troubleshooting DC motor systems.

maxstag
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Hi,

I am currently doing my Master project and unfortunately did a rookie mistake.
My DC motor is mechanically linked to a loaded PMA (wind turbine generator) and I need to run it at a variable speed. All this is built, however when choosing my PSU, I forgot to take into account the stall current (which was unfortunately not indicated in the motor's datasheet. My motor is rated at around 600W (3/4 HP to be precise) with 24V (so a current of 25A). My PSU is the same, 24V and 25A rated. My whole system is built, the motor starts for 1 second and then the PSU stops working (very probably due to overloading). I am therefore unable to start my motor at all.

Would any of you have a solution for me to jump-start my motor without having to replace the whole PSU (which is quite expensive)? I still do not have a measurement of stall current, but I ordered a meter shunt to help make my measurements.

Datasheet:
OMPMDC34-18-24V-56C :
http://www.omega.com/Auto/pdf/OMPM-DC.pdf

Thank You for your help.

maxstag
 
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The quick and dirty solution would be a 1 ohm series resistor rated about 600 watt. Instead of a resistor, I would consider using 24V 100W truck headlamp globes, maybe 4 to 6 of them in parallel. That will limit current during start-up, globes will then go dim and low resistance once motor is running. Maybe a parallel switch to short the globes for maximum power.

Alternatively, make a switching current limiter.
 

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