What is the difference between continuous current and peak current?
Continuous current is the value a driver can carry indefinitely; peak current is a short pulse tolerated only for the stated duration. On the KS250 these values are 15 A continuous and 45 A peak (5 seconds), on the PT500 30 A continuous and 40 A maximum (15 seconds). Sizing is always done according to the continuous current.
The difference between the two values is thermal. Conduction loss grows as P = I² x R; doubling the current quadruples the loss. The level at which the driver can shed this heat permanently is defined as the continuous current. Peak current, on the other hand, is a pulse the board can carry briefly thanks to its thermal inertia, and which must end before the temperature reaches a dangerous level.
In motor applications the peak current is no accident: at start-up the rotor is stationary, there is no back-EMF, and the motor behaves like a shorted load. The starting current is typically 5-8 times the rated current and lasts 0.5-3 seconds.
Product figures:
- KS250: 15 A continuous, 45 A peak, peak duration 5 seconds.
- PT500: 30 A continuous, 40 A maximum, duration 15 seconds.
The most common mistake is selecting according to the peak value. If your motor continuously draws 20 A, a module that can deliver 45 A peak cannot carry it; what matters is the continuous value. Use the peak value only to check whether the starting pulse can be handled, and make sure the pulse fits within the stated time window.
The full topic: DC Motor Driver Selection Guide