maxon contrôleurs: Signification du calibre "Basse température" ?

Ce document n'est actuellement disponible qu'en anglais.

Topic:

• What is the meaning or impact of the specified "Low temperature" operation rating of motor controllers (or electronics in general)?
• What will happen if the system's environmental temperature is lower than the controller's specified "low temperature operation" value (e.g. -30°C for most controllers)?
• Is the low temperature limit checked by a temperature sensor triggering an error state?
• Can the specified value be lowered even further by some firmware modification?

Basics:

The specified low temperature limit of maxon controllers (typ. -30°C) is not checked by a sensor which triggers an error state or blocks the controller's functionality. It is a "malfunction" which happens due to the fact that some electronic components will not work reliable anymore below the specified "Temperatur - operation" limit. Such a "malfunction" can by typically observed if the controller has to boot-up after some period of power-down and being exposed to an environmental temperature below its "low temperature" rating. The controller (and its processor) will not be able to start at all in most cases. There is also no indication of an error state or any communication possible at such a state. The controller seems to be "dead".

• Any specified "low temperature" limit is due to electronic components' temperature rating. Below this temperature limit, any proper and reliable operation of the electronics can no longer be assumed.
  • Electronic components (e.g. quartz, DC/DC converters, processors, ...) might not work properly  (or not at all) below their specified low temperature limit (which is typically -30°C for standard electronic components and most processors). 
  • One typical problem is that the quartz might not start anymore, i.e. as a consequence all other clocked components (such as the processor) are non-functional too, i.e. no error or status display and in principle no data processing, control, and communication is possible. The controller appears like "frozen" in the truest sense of the word. 
    
    
• If a low temperature limit of -30°C is specified, the "malfunction" or blockage to start-up the electronics can happen at -31°, -32°, -35° or any lower temperature. 
  • The malfunction is not linked to one discrete precise temperature value. It depends on components' tolerances too. 
  • The correct function of the motor controller below its specified "low temperature" limit is no longer guaranteed. 
  • In case of a specified -30°C low temperature limit, the controller might typically fail at -35° or at -40°C latest but it can also fail already at -31°C. The only "safe" operating temperature range is therefore at -30°C or warmer. 
    
    
• There is no possibility to simply assign an existing controller design to a lower operating temperature range (e.g. -40°C instead of -30°C). Any lower temperature requirement means a redesign of the electronics and usage of specialized components specified for operation at low environmental temperatures (e.g. -45°C).
  • There is only a fairly limited choice of components for operation at very low temperatures. Most electronic components and plastics (e.g. of connectors or LEDs) are rated for -30°C.
  • Especially the plastics of connectors and LEDs or DIP switches but also electronic components' housings get brittle in case at very low ambient temperatures, i.e. these components also fail if  they are exposed to very low temperatures over a longer period of time. 
  • If there is a demand for lower environmental temperatures than -30°C, there have to be quite often special purpose controllers and electronic components in use based on "military" specifications. There is a much more limited selection of such components present and the price is much higher than accepted by standard catalog products.

Conclusion:

The specified low "Temperature - operation" limit cannot(!) be shifted further down by a parameter configuration or firmware modification. Such a requirement means a new adapted electronic design and the use of specific electronic components for the required lower temperature range.

Practical hint:

If there is an environmental temperature present below -30°C but the controller is just rated for -30°C low temperature operation, the motor controller (e.g. ESCON or EPOS4) has to be slightly heated up to its specified low temperature range before power on. This might be possible by some surrounding heating mat.  

• After boot-up has worked well (due to an "external" heating), the electronics will continue to work in most cases even if the external heating is deactivated. The heat generated by the electronic components during operation is often sufficient to keep them "alive" even if the environmental temperature stays 5 - 10°C below the controller's specified low limit of "Temperature - operation".
  
  
• At low temperatures or strongly varying ambient temperatures condensing humidity can occur on warm components (= electronics) and lead to short circuits and a malfunctions too. In this case some conformal coating of the electronics is required to reduce the risk of short circuits caused by (condensing) humidity.