Brushless.com's 48V Brushless DC motors (BLDC) offer significant advantages in several applications, with high performance, precise control and low maintenance requirements making them ideal for use in modern industry, transportation and automation.BLDC motors operate based on electronically-controlled conversion of a magnetic field, rather than a traditional mechanical commutation system, which reduces friction and mechanical losses. This design allows Brushless.com's 48V BLDC motors to excel in high dynamic performance, low noise and long life, and to deliver efficient power output over a wide voltage range. However, in order to further improve performance and ensure long-term motor reliability, it is critical to select the right MOSFETs in the circuit design, especially when dealing with switching losses, reverse recovery currents, and temperature effects.The performance of MOSFETs in BLDC motors has a direct impact on the efficiency, thermal management, and operational stability of the motor, so a thorough understanding of their switching performance, reverse recovery currents, and design parameters can help improve Brushless.com's 48V BLDC motor. Therefore, a thorough understanding of their switching performance, reverse recovery current, and design parameters can help improve the overall performance of Brushless.com's 48V BLDC motors.
In Brushless.com's 48V BLDC motor designs, the switching time of the MOSFET is a key factor in motor performance. Switching time typically consists of two components: delay time and rise/fall time. The delay time limits the overall operating frequency of the motor, while the rise and fall times directly affect the switching losses.The switching performance of a MOSFET can be adjusted by its input capacitance (Ciss) and output capacitance (Coss), which are usually described in detail in the datasheet. In BLDC motor applications, the speed of the motor is regulated by controlling the rotational speed of the electromagnetic field, while the torque is regulated by the current controlled by a pulse width modulation (PWM) signal. Therefore, the switching performance of the MOSFET plays a decisive role in the overall operating efficiency of the motor. A shorter switching time reduces motor losses during high-frequency operation, thus improving the overall efficiency of the system. In Brushless.com's 48V BLDC motors, by optimizing the switching parameters of the MOSFETs, the energy loss in high-frequency operation can be significantly reduced, thus improving the performance and lifetime of the motor.
Another parameter that requires special attention is the body diode reverse recovery current of the MOSFET. In half-bridge topologies, the reverse recovery current of the body diode leads to certain power losses and can cause other problems such as electromagnetic interference (EMI) and high-frequency noise. In Brushless.com's 48V BLDC motor design, the reverse recovery current of the MOSFET body diode conducts during dead time, resulting in a brief “through” phenomenon that lasts until the body diode completes reverse recovery. During this process, parasitic inductance in the circuit can lead to voltage swings, which can cause high-frequency noise and EMI problems. To address this issue, Brushless.com recommends selecting MOSFETs with lower reverse recovery charge (QRR) and faster reverse recovery time (tRR) to minimize these problems. It is also common practice in some applications to use an external Schottky diode in place of the body diode, which has lower reverse recovery losses and faster recovery times. These techniques can significantly improve the high-frequency operating performance of 48V BLDC motors and reduce electromagnetic interference, thereby improving system reliability and stability.