C
Sir,
I am driving a 24V,1500rpm BLDC motor with a per phase resistance of 0.3 ohms and inductance of 335mH (max current allowable=7amps). The transistors in the three phase inverter are IRF3710 (total gate charge of 130nC). The inverter is being driven by three (one for each leg of the inverter) driver IC's IR2101 with a bootstrap capacitor value of 0.44uF, 50V. The ICs are connected to the Gates of the Mosfets with 100ohm resistors.The 12V power supply required for the ICs comes from a 7812 voltage regulator with an input of 24V. The PWM frequency is 20Khz. The control logic (PWMs) for the ICs are derived from a National Instruments controller (cRIO-9074)with Labview. Speed control is done by varying the duty ratio. With these circuitry in place, I am facing the following problems:
1. The inverter is not giving me enough power i.e. at a duty ratio of 95%, when the speed should be around 1300rpm or so, it gives me a speed of only 400rpm.
2. When I try to load the motor, it slows down further horribly. (I haven't implemented any closed loop control schemes, which is my ultimate aim.
3. The motor makes a somewhat disturbing shrill noise when running.
I am not facing any of the above problems if I run the motor with an off-the-shelf controller. I would be grateful if somebody could point out a remedy.
I am driving a 24V,1500rpm BLDC motor with a per phase resistance of 0.3 ohms and inductance of 335mH (max current allowable=7amps). The transistors in the three phase inverter are IRF3710 (total gate charge of 130nC). The inverter is being driven by three (one for each leg of the inverter) driver IC's IR2101 with a bootstrap capacitor value of 0.44uF, 50V. The ICs are connected to the Gates of the Mosfets with 100ohm resistors.The 12V power supply required for the ICs comes from a 7812 voltage regulator with an input of 24V. The PWM frequency is 20Khz. The control logic (PWMs) for the ICs are derived from a National Instruments controller (cRIO-9074)with Labview. Speed control is done by varying the duty ratio. With these circuitry in place, I am facing the following problems:
1. The inverter is not giving me enough power i.e. at a duty ratio of 95%, when the speed should be around 1300rpm or so, it gives me a speed of only 400rpm.
2. When I try to load the motor, it slows down further horribly. (I haven't implemented any closed loop control schemes, which is my ultimate aim.
3. The motor makes a somewhat disturbing shrill noise when running.
I am not facing any of the above problems if I run the motor with an off-the-shelf controller. I would be grateful if somebody could point out a remedy.
