Related to "key vehicle electrical"

Thermocouples are widely used in automotive industry for temperature testing at product design and EOL (End of Line) stages and for permanent monitoring afterwards. However, with the increasing voltage levels in Emobility thermocouples possess many risks in product design and testing stages. Some of them are safety related risk and have potential to be life threatening for employees (research and test engineers).

Thermocouples are based on the principles, that a small voltage (in milli-volts) gets produced when a junction (joint) of two dissimilar metal wires is cooled or heated. The generated voltage signal is measured at the other end of the metal wires and calibrated for the temperature range. During the temperature testing the junction end is put on the test object and voltage is being measured at the other end to estimate the temperature of test object.

Now imagine if the two metal wires are put on the 1000 V Battery or Motor for temperature testing and somehow the test engineers touch the wire by mistake. Even worse how accurate will be the milli-volt signal when it passes through an environment where there is high electric and magnetic field.

Without getting into more technicality let us take a closer look on the common reasons why thermocouples have failed in Emobility testing and should be replaced with intrinsically safe sensors.

1. Safety

It is very obvious and common sensical thing to find out the safety risk of using thermocouples in Emobility testing, especially when test engineers have to adjust sensing location such as finding the right hot spot or reach to the measuring points that are not easily accessible (Inverters, Stator Windings, Battery Cooling duct). Thermocouples are subject to creating a short circuit and electrocution risks to the employees.


2. Noise

With the Emobility going towards 1000V and even higher 2500V (for commercial vehicles), thermocouples are highly susceptible to noise. The milli-volt signal requires lot of isolation under such large voltages and even then, the signal is not clear enough to measure accurate temperature.



3. Larger Size  

Thermocouples are not suitable for Emobility applications that has very tiny space for putting sensors such as Charging Points, Invertor IGBTs, Battery Inter-cell temperature measurement etc. It has been observed that thermocouples are less responsive and inaccurate (up to 20 to 30 Deg Celsius) if they are not put directly on the charging points. 


4. Non-Linearity Over The Range  

Though the thermocouples are calibrated for a certain range, they still need complex compensation algorithm to maintain linearity over the range since they are being used at harsh conditions (High electric, chemical and magnetic fields) and different test environments.



5. Longer Response Time  

Faster and accurate measurement is critical for Emobility during the performance, life cycle and abuse testing. Not only the accuracy, thermocouples are also limited by the response time requirements of Emobility applications such as detection of Thermal Runaway Issues, Charging Point Temperature, Stator Winding Temperature etc.


6. Poor Repeatability 

Thermocouples are made of two dissimilar metallic wires and susceptive to material purity which varies from batch to batch and manufacturer to manufacturer. This variation creates calibration issues resulting into non-repeatability of accurate measurements. Further the chemical composition of metal changes with time especially if they are put into chemical environment like Batteries.


Description:

Thermocouples are widely used in automotive industry for temperature testing at product design and EOL (End of Line) stages and for permanent monitoring afterwards. However, with the increasing voltage levels in Emobility thermocouples possess many risks in product design and testing stages. Some of them are safety related risk and have potential to be life threatening for employees (research and test engineers).

Thermocouples are based on the principles, that a small voltage (in milli-volts) gets produced when a junction (joint) of two dissimilar metal wires is cooled or heated. The generated voltage signal is measured at the other end of the metal wires and calibrated for the temperature range. During the temperature testing the junction end is put on the test object and voltage is being measured at the other end to estimate the temperature of test object.

Now imagine if the two metal wires are put on the 1000 V Battery or Motor for temperature testing and somehow the test engineers touch the wire by mistake. Even worse how accurate will be the milli-volt signal when it passes through an environment where there is high electric and magnetic field.

Without getting into more technicality let us take a closer look on the common reasons why thermocouples have failed in Emobility testing and should be replaced with intrinsically safe sensors.

1. Safety

It is very obvious and common sensical thing to find out the safety risk of using thermocouples in Emobility testing, especially when test engineers have to adjust sensing location such as finding the right hot spot or reach to the measuring points that are not easily accessible (Inverters, Stator Windings, Battery Cooling duct). Thermocouples are subject to creating a short circuit and electrocution risks to the employees.


2. Noise

With the Emobility going towards 1000V and even higher 2500V (for commercial vehicles), thermocouples are highly susceptible to noise. The milli-volt signal requires lot of isolation under such large voltages and even then, the signal is not clear enough to measure accurate temperature.



3. Larger Size  

Thermocouples are not suitable for Emobility applications that has very tiny space for putting sensors such as Charging Points, Invertor IGBTs, Battery Inter-cell temperature measurement etc. It has been observed that thermocouples are less responsive and inaccurate (up to 20 to 30 Deg Celsius) if they are not put directly on the charging points. 


4. Non-Linearity Over The Range  

Though the thermocouples are calibrated for a certain range, they still need complex compensation algorithm to maintain linearity over the range since they are being used at harsh conditions (High electric, chemical and magnetic fields) and different test environments.



5. Longer Response Time  

Faster and accurate measurement is critical for Emobility during the performance, life cycle and abuse testing. Not only the accuracy, thermocouples are also limited by the response time requirements of Emobility applications such as detection of Thermal Runaway Issues, Charging Point Temperature, Stator Winding Temperature etc.


6. Poor Repeatability 

Thermocouples are made of two dissimilar metallic wires and susceptive to material purity which varies from batch to batch and manufacturer to manufacturer. This variation creates calibration issues resulting into non-repeatability of accurate measurements. Further the chemical composition of metal changes with time especially if they are put into chemical environment like Batteries.


Related Keyphrases:

two dissimilar metal wires | two dissimilar metallic wires | Emobility thermocouples | permanent monitoring afterwards | generated voltage signal | temperature measurement | complex compensation algorithm | Emobility applications | Stator Winding Temperature | Charging Point Temperature | response time requirements | test engineers touch | temperature range | accurate measurements | accurate measurement

Description:

Predictive maintenance (PdM) techniques are designed to help determine the condition of in-service equipment in order to estimate when maintenance should be performed. This approach promises cost savings over routine or time-based preventive maintenance, because tasks are performed only when warranted. Thus, it is regarded as condition-based maintenance carried out as suggested by estimations of the degradation state of an item.[1][2] The main promise of predictive maintenance is to allow convenient scheduling of corrective maintenance, and to prevent unexpected equipment failures. The key is "the right information in the right time". By knowing which equipment needs maintenance, maintenance work can be better planned (spare parts, people, etc.) and what would have been "unplanned stops" are transformed to shorter and fewer "planned stops", thus increasing plant availability. Other potential advantages include increased equipment lifetime, increased plant safety, fewer accidents with negative impact on environment, and optimized spare parts handling.

Related Keyphrases:

prevent unexpected equipment failures | equipment needs maintenance | increased equipment lifetime | corrective maintenance | Predictive maintenance | preventive maintenance | maintenance work | increased plant safety | potential advantages | plant availability | right information | approach promises | degradation state | allow convenient | fewer accidents

Description:

Thermocouples are widely used in automotive industry for temperature testing at product design and EOL (End of Line) stages and for permanent monitoring afterwards. However, with the increasing voltage levels in Emobility thermocouples posses many risks in product design and testing stages. Some of them are safety related risk and have potential to be life threatening for employees (research and test engineers).

Researchers and testing experts in Emobility have seen the following major challenges with using Thermocouples for temperature testing in high voltage applications.

  1. Safety: Thermocouples are subject to creating a short circuit and electrocution risks to the employees.
  2. Noise: With the Emobility going towards 1000V and even higher 2500V (for commercial vehicles), thermocouples are highly susceptible to noise.
  3. Linearity: Though the thermocouples are calibrated for a certain range, they still need complex compensation algorithm to maintain linearity over the range
  4. Response Time: Thermocouples are not fast enough and accurate for thermal profiling of key components of Electric Vehicles such as Charging Points, Battery, Motor Windings and Power Electronics.
  5. Repeatability: Thermocouples are made of two dissimilar metallic wires and susceptive to material purity which varies from batch to batch and manufacturer to manufacturer.

Related Keyphrases:

permanent monitoring afterwards | complex compensation algorithm | two dissimilar metallic wires | Emobility thermocouples | electrocution risks | commercial vehicles | automotive industry | rangeResponse Time | Electric Vehicles | major challenges | product design | material purity | voltage levels | Charging Points | key components

Description:

Temperature management is one of the most important part in the design, development and testing process of electric / hybrid vehicles. The performance and aging of all critical components of electric vehicle highly depend on the temperature distribution and developing hot spots within. Therefore,  faster and accurate temperature measurement is necessary at each stage of EV product development e.g. individual component level testing for identifying performance limits and temperature behavior of individual components, and fully assembled electric vehicles to ensure the overall performance and safety.

Electric / Hybrid vehicle design and architecture differs a lot from the traditional Petrol and Diesel vehicles. The shift from low voltage to high voltage (up to 1000V) connections and operations within the similar vehicle space (or some time lesser space) bring challenges in terms of safety, limited access and electromagnetic noise issues during testing and measurements. Fiber Optic technology based sensors e.g. Fiber Optic Temperature sensors are becoming more and more popular in testing Electric / Hybrid vehicles due to their immunity to electromagnetic field, ruggedness, smaller size, faster response, high accuracy and safety of operation.

Related Keyphrases:

Fiber Optic Temperature sensors | accurate temperature measurement | electromagnetic noise issues | individual component level | temperature distribution | Hybrid vehicle design | Fiber Optic technology | similar vehicle space | individual components | Temperature management | EV product development | Hybrid vehicles due | electric vehicles | electromagnetic field | overall performance