![]() ![]() Low PWM frequencies of a few thousand Hertz may generate rotor vibrations and audible noise. Therefore, the rotor of the motor itself will not have enough time to react when the voltage is switched at typical PWM frequencies. However, the mechanical time constant is in the range of a few milliseconds, so there is a factor of 10 between the mechanical and the electrical time constant. The current will therefore have the time to react during each PWM cycle (see Figure 11). Courtesy: Portescapīrushless dc motors have an electrical time constant τ of a few hundred microseconds. Most of the time, chopper amplifiers are using a PWM method.įigure 10: Exponential current fall in an RL circuit. This helps conserve the battery life of the application, produces less heating from the electronics and allows for smaller electronics size. The primary advantage is it saves power when the transistor is off. As a result, a large heat sink is required to dissipate the power, increasing the amplifier size and making it more difficult to integrate in the application.Ī chopper amplifier modulates the voltage (and current) by switching the power transistors on and off. The power that is not delivered to the motor is dissipated (lost power, see Figure 6). Linear amplifiers adapt the power delivered to the motor by changing the voltage or current. Chopper drivers (or linear amplifiers). ![]() There are often two different ways to vary the voltage or the current: The amplifier’s role is to vary the supply voltage or the current, or both, to achieve the desired motion output. In a brush (see Figure 5) or a brushless dc motor (see Figure 6), the working point (speed and torque) of an application can vary. Courtesy: Portescap PWM regulation for brushless dc motors Figure 4: Phase current using an FOC amplifier. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
December 2022
Categories |