How long is the PT500's 40A maximum current tolerated?
The PT500's 40 A maximum current rating is defined for a duration of 15 seconds; the continuous operating rating is 30 A. This 15 second window is for the starting pulse and short overloads, it is not a continuous operating regime. For sustained loading, size according to the 30 A limit.
The values in the PT500's product data: 12-24V DC, 30 A continuous, 40 A maximum, duration 15 seconds. The 15 second window is wider than the KS250's 5 second window; this difference can be decisive on heavy-duty motors with a slow start and on loads with a high moment of inertia.
In practice, use the 15 second window as follows:
- Measure the starting pulse with the real load. It is typically 5-8 times the nominal current with a duration of 0,5-3 seconds; this pulse stays well inside the window.
- To reduce the pulse, lengthen the ramp time with the RMP pot. A soft start typically brings the pulse down to 2-4 times the nominal current.
- In applications with back-to-back starts, leave time for the board to cool between the peaks.
What matters is this: the maximum current rating does not define the driver's capacity. If the current your motor draws steadily under load exceeds 30 A, choosing the PT500 by looking at the 40 A figure would be wrong. Always size according to the 30 A continuous rating, leaving a safety margin on top.
Full topic: DC Motor Driver Selection Guide