I need to kinda soft-start an array of fans, all connected to one reference PWM. The problem is our fans at top speed can roughly draw 2.5 times as much power as our DC-source can handle (on-board custom PCG for an inverter not easily replaceable). And of course, they also draw a lot of power during start-up.
We got 4-wire fans, so I plan to use a PWM to control their speed, this works fine after start-up, but during the start-up the fans will draw a lot more power even when setting the duty-cycle to 10%. Are there any tricks I can use? Does the PWM frequency affect the start-up? Due to small differences between the fans (6 in total) they also won’t start synchronous, this affects changes in the duty cycle too, their speed will vary for a couple of seconds (also shows in power consumption).
PWM 10-100% (Max for our dc-source is around 55%)
So basically what is better in such a case a high or low frequency PWM? Also have you any recommendations at how fast I should change between duty-cycle levels?