An Investigation into the Lifespan of Brush DC Motor with Different Oil Properties

Abstract

 A DC motor is an electromechanical device that converts electrical energy to mechanical torque. DC motors are widely used in industry and electrical appliances such as adjustable seats and electric toothbrushes. However, DC motors have a short lifetime and applying lubricant is one of the solutions for this problem. This study aims to determine the properties of oil that are suitable for lubrication and compare the maximum speed, lifetime and final temperature of a DC motor after applying different lubricants and without applying any lubricants. Two different oils (Oil A and Oil B) with different properties were used in this experiment. Each motor in this experiment needed to be run and stopped for 3-minute intervals and repeating this cycle until the motor’s RPM was dropped. The results show that both oils have the same density, that is 840 kg/m3 but the viscosity of the oil is different that is, 2.081×10-5 m2/s for oil B compared to 2.497×10-5 m2/s for oil A by using a 1.590 mm diameter steel ball. This experiment also shows that by applying lubricant, it increases the maximum speed and the lifespan of the DC motor. The lifespan for the DC motor with oil B to maintain its maximum speed of 28500 RPM is longer, which is 13 cycles, or about 39 minutes, while the DC motor with oil A could maintain its maximum speed of 27500 RPM for only 12 cycles, or 36 minutes. Therefore, the motor with lubricant that has a lower viscosity (Oil B) gives a better result than the motor with a higher viscosity lubricant (Oil A) in terms of maximum speed, lifetime and the rise of the DC motor temperature is between 37.7°C and 39.5°C not exceeding 40°C.