I’m new to the world of DC brush motors.
Assume I have a 5V supply supplying an H-bridge which drives a motor rated at 3V. If I keep my PWM rate under 60%, will the motor be happy?
In other words, is the 3V rating really about average power (in which case my PWM approach should be fine), or is it really an absolute voltage rating?
… or should I just go ahead and buy a batch of motors and see how long they last?
In general, voltage ratings from brushed DC motors are not hard limits; there are typically a range of voltages you can use, and the higher the voltage, the shorter the motor lifespan will be. You might find this article written by a forum member interesting:
Limiting the average voltage by keeping your PWM duty cycle below 60% should be fine as long as you are using a sufficiently high-frequency PWM (i.e. one that keeps the current relatively constant throughout the entire PWM period).
I saw that post about over-voltage and lifetime. If anything surprised me, it was that a 3V motor driven at the recommended voltage failed after 76 hours.
My PWM circuit will have soft start and stop – it would be interesting to see if that affects the lifetime.
Thanks for the info.