How long can the KS250's 45A peak current be drawn?
The KS250's 45 A peak current value is defined for a period of 5 seconds. Its continuous rating is 15 A. If the starting pulse lasts longer than 5 seconds or is repeated frequently, the application is too heavy for the KS250; the PT500, which gives 30 A continuous and 40 A maximum (15 s), should be considered.
The values stated in the KS250's product data are clear: 15 A continuous, 45 A peak and a peak duration of 5 seconds. These 5 seconds are for short events such as a starting pulse, a sudden load or a direction change; it is not a repeating operating regime.
To understand whether your application fits into this window, run the motor with its real load and measure the starting current and its duration. In DC motors the starting current is typically 5-8 times the nominal current and the duration is of the order of 0.5-3 seconds depending on the load and inertia. In most door, curtain and actuator applications the pulse is in this range and stays within the 5 second window.
The most practical way to reduce the pulse is to use the KS250's ramp (soft start and stop) function. A ramped start brings the pulse down to typically 2-4 times the nominal current; it both relieves the peak window and reduces mechanical strain.
Watch out for the following:
- Do not plan continuous operation according to the peak value; the determining value is 15 A.
- If starts are made one after another at short intervals, the board cannot find time to cool between the peaks.
- If the requirement exceeds 5 seconds, the PT500's 15 second window is more suitable.
The full topic: DC Motor Driver Selection Guide