Thermal control in Motor Controllers

One of the most important points when designing a power electronic system is efficiency. An improvement in efficiency reduces the risk of breakage in the long term, as losses are converted into heat and this heat needs to be dissipated in some way.

Embention’s Motor Controllers have been designed from the first moment under this concept. The hardware is not the only important aspect, the software also influences thermal control. At Embention we have implemented FOC (sinusoidal switching) in all our ESC products, optimizing thermal control in motor controllers for eVTOL from the earliest stages of design.

Software control for thermal control in motor controllers

To give a visual explanation on how the type of software control affects the thermal control in motor controllers, ​​we have represented it in the two images below. In the first image the type of control is block switching and the second is FOC switching.

This is because the ESC dissipates its energy mainly in 3 ways:

a) Conduction of the intrinsic diode

b) Switching losses

c) Loss of conduction

One of the most frequent break points in ESCs is the diode, especially when regeneration is used, using the FOC algorithm it is possible to reduce the driving time and to increase the reliability of the system. Thermal control in motor controllers extends the lifetime of these systems and the safety in eVTOL aircraft. Continuing with the comparison between block commutation and sinusoidal commutation, below we can observe the percentage of total losses in both cases.

Another important point in thermal control in motor controllers is when the ESC is used in environments with very little air flow. This problem is solved by using a material with very high emissivity, around (ε = 0.85). All Veronte eVTOL Motor Controller drivers have an anodized aluminum heatsink.

One of the weak points of those designs in which there is an external connection (battery and motor) is the connection point. Embention uses a technology in which tin is not used (very high electrical resistivity), instead of this, pressure is used to join the connector to the electronic board.

The Veronte Motor Controller has all kinds of temperature sensors, being able to save data and send alarms in the event of significantly high temperatures, allowing it to avoid reaching the maximum safe operating temperature. If this is not possible, Veronte’s ESCs have mechanical fixings for the installation of a fan. This is useful when it is installed indoors and / or when there is no air flow.

A decrease in operating temperature increases the life of the internal capacitors. In fact, this is the component that determines the maximum life of the electronics of all devices. A capacitor working at its maximum temperature can decrease its useful life by up to 10 years. This is one of the main reasons why thermal control in motor controllers is especially important. In order to ensure maximum durability and reliability, the motor controller must be designed so that the working temperature is always the minimum. That is why Embention always recommends installing the ESCs in the propeller flow of the vehicle or in a place with a constant air flow.

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