Electronic power equipment generate heat and shall be appropriately cooled, because failures may burn equipment and start a fire.
Natural cooling is to be preferred because it avoid the risk associated with fan failure, but is not always possible.
It is preferable to have electronics installed in a naturally ventilated area, vertically to create a natural convection airflow. Enclosing them properly may help good airflow guiding.
Component datasheet requirement shall be respected, meaning that if for the most penalising case, there is a requirement for a heatsink, it shall be installed. Low cost equipment may not always comply with datasheet, so better cooling than theorically required place you on the safe side. Components which need a careful review against their heating are :
- Voltage regulators
- DC/DC SSR
Stepper driver generally incorporate temperature safety, but they may need good cooling.
Dissipated power rise as the square of the current, so increasing size/power of an equipment shall be done with caution.
Basic power generated by continuous current on FET can be evaluated as W = Rds(on)*I²
PWM control increase the generated heat.
Example : for a heat bed of 200W supplied in 12V, I = 16.66A.
If resistance of the driving FET -Rds(on)- is 0.047 Ohm, power is 13W, and the FET shall heatsinked and well cooled to not burn. Another board using a FET with 0.0032 Ohm will dissipate only 0.89W, and may not need heatsink at low frequency PWM.
If a SSR is used, the power is 'Voltage drop'*Current.
With a SSR voltage drop of 1.5V, the bed power is reduced to 153W and the current to 14.6 A. With this current, the SSR dissipated power will be 22W, needing serious heat-sinking and cooling.
A fire proof box is desirable for safety, and if well designed it could be a good airflow guide for electronic board. See how power supplies are built. Using a salvaged power supply box is a solution.
- Board safety
- Power supply
- Choosing a Power Supply for your RepRap