Design and Control of a Light-Weight Drive-Integrated 48 V BLDC Motor for Radiator Fan in Hybrid Vehicle

In small car segment, as far as hybridization is concerned, the space and safety constraint demands use of lower voltage viz., 48 V as compared to >100-volt-systems used for vehicles in other segments. These systems also have advantage of reduced copper weight due to reduced current. As 12 V systems are replaced by the 48 V systems, the auxiliary 12 V loads would necessitate implementation of a DC-DC converter. Considering the requirements of auxiliary loads that are fed from 12 V battery, the power rating of the DC-DC converter can get considerably high resulting in increased size. Hence, it is advisable to re-design at least some of the 12 V auxiliary systems to 48 V such as the radiator fan motor. This, along with the issues faced in the existing PMDC Motor with regard to efficiency and sizing have generated interest to investigate better alternatives for the motor. To this end, this paper describes the design, development and control of a Brushless DC Motor to be used as a radiator fan. The improved design results in weight reduction and increase in percentage efficiency by about 30 compared to the conventional DC Motor. In addition, issues like sparking and maintenance of brushes for a 48 V DC motor are also eliminated. A low-cost integrated PCB controller is developed to implement the control strategy using Microchip PIC 2231 micro-controller. Finally, the drive is implemented and tested with the radiator fan and the results are presented.