Should I buy a 15A driver or a 30A driver, and how do I decide?
The decision is made by looking at the motor's real continuous current under load and at its starting surge. If the measured continuous current approaches the 15 A figure of the KS250, or if the starting surge pushes past 45 A for longer than 5 seconds, move to the PT500, which gives 30 A continuous and 40 A maximum (15 s).
Three measurements determine the decision:
- Continuous current under load. Run the motor with its real load and measure with a clamp meter. Note the steady operating value, not the instantaneous highest value.
- Starting surge. The starting current is typically 5-8 times the nominal current and lasts 0.5-3 seconds. A ramped start typically reduces this surge to 2-4 times the nominal current.
- Duty cycle. A door running continuously at short intervals is not the same as a shutter running a few times a day.
Then compare with the product figures:
- KS250: 15 A continuous, 45 A peak (5 seconds).
- PT500: 30 A continuous, 40 A maximum (15 seconds).
If the measured continuous current approaches 15 A, no safety margin is left; moving to the PT500 is the right choice. If the starting surge lasts longer than the KS250's 5-second peak window, the PT500 should again be preferred. On the other hand, if your continuous current is clearly below 15 A, the KS250 is both sufficient and more compact (120x40x46 mm, 110 g).
Full topic: DC Motor Driver Selection Guide