Table 2 Advantages and limitations of different cooling methods

Conduction

• Good with low current density systems.

• No moving parts required.

• Can be coupled with convective cooling methods.

• There is a limit to how much heat transfer material is to be used.

• Not suitable for high current density values.

• Significant increase in system weight if more heat conductive material is added.

• Eddy currents in case of excess material [42] and from changing fields

Air cooling

• Cooling medium is readily available.

• Can easily be coupled with conductive cooling and indirect liquid cooling.

• Dry method hence no fear of shocks from leakage.

• Limited to current densities of 2 A/mm².

• Low coefficient of heat transfer (between 2.5–10 (natural convection) 10–500 W/m²K (forced convection) [64]).

• Often bulky with high space requirements.

Liquid cooling

• Relatively high coefficient of heat transfer (100–15,000 W/m²K [64])

• Compact design is possible hence lower space requirements.

• No thermal barriers when direct cooling through hollow conductors is used

• Possible electric shocks in case of leakages

• Corrosion of cooling channels due to high flow rate and pressure requirements

• Additional power and operational costs from pumping