Heatsinking

All electrical items carrying current get hot. The amount of heat generated is proportional to the square of the current, so doubling the current causes four times the heat. A high current motor and controller can draw a lot of current and so can generate a lot of heat. For these, proper heatsinking and cooling is important.

Motors – at least the ventilated ones – often have a built in fan for cooling, controllers usually do not. So a motor can generally be used at higher currents for longer than a controller since the heat will build up in the controller while the motor cools itself.

Fortunately, most controller applications are land based and very ´peaky´: a machine on land generally only takes a lot of current to get up to speed or to climb a hill, both are usually only a few seconds.

This peaky heat generation is well suited to MOSFET technology and all controllers therefore tend to be rated for peaky use. To make a controller for continuous use, you either need to use a lot more power devices – i.e. use a bigger controller, or take steps to remove the heat quicker. Boats and other water craft need a continuous rating since the faster you go, the more the current: it takes power simply to move through water, not just to get up to speed.

The moral is: use a controller that will give a top current output perhaps 2 – 3 times the continuous motor current and do not expect a controller to run continuously at more than 30-50% of its short term rating. If you are running at high duty cycles then consider fitting additional cooling or heatsinking, we have suggestions as to how on this page.

4QD now have finned air and water cooling solutions for the Pro-360 series, and can also fit the larger DNO heatsink to the Porter range.

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