The Electrification of commercial vehicles is happening at a rapid pace. Most of the major automotive corporations are pursuing this opportunity to include electric vehicles in their portfolios. The commercial trucking industry has also been exploring the use of electric vehicles for goods transport including perishables. The transition to electrically driven vehicles has led to the need for electrically driven HVAC systems. To support this evolving commercial market, we developed an electrically driven variable speed compressor platform comprising of compressor and variable frequency drive (VFD). The product platform addresses two categories of vehicles: 1) Hybrid vehicle – the vehicle in this category uses conventional IC engine and has traditional batteries that output 48VDC. 2) Electric vehicle – the vehicle in this category is electrically driven using battery bank or traction drive that gives 650VDC as output. Hence, 650V DC is input to VFD. Both these applications were addressed with two drive designs.

In this paper, we discuss the thermal design aspects of both 48V and 650V variable frequency drives. In this publication, the product development process is described from product conception, to final product. The mechanical / environmental design considerations while designing these drives were, (1) The drive was expected to be mounted under the vehicle bed and hence should be strong enough to withstand shock and vibration, (2) the drive was decided to be air cooled (4) the drive was designed to be IP67 so that it can withstand harsh road conditions, (5) the desired operating temperature range was between −40°C to 85°C for 48V and −40°C to 65°C for 650V and (6) the estimated time of service was expected to be 10 years. We were able to achieve an operating margin of −40°C to 70°C at full load for hybrid vehicle drive (48VDC) and −40°C to 65°C for electric vehicle drive (650VDC) using air cooling.

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