Why does my brushless motor not reach rated speed?
I have already configured my motor completely with the Configuration Wizard (or manually) but when I try to move the motor, I can see that it clearly does not reach its rated speed. Why does that happen and what can I do about it?
Before introducing what changes we need to do, let's understand a concept regarding the commutation of brushless motors. As you might know, you can commutate a brushless motor with an Ingenia servo drive in two different modes depending on the feedback device: trapezoidal commutation (BLDC mode) and sinusoidal commutation (BLAC mode). The first one is less efficient as far as commutation is concerned but is able to reach higher speeds due to a higher DC bus utilization factor and the second one reaches less maximum speed but with a way higher efficiency.
Having said this, let's see how we can make this differentiation inside MotionLab and how to configure our drive so that our motor can reach its rated speed. We are going to be using the following Motor parameters as an example:
If your motor only has hall sensors as the only feedback device, you will be automatically doing trapezoidal commutation (it is the only possibility) and will reach the maximum speed without problems. Otherwise, it is either a tuning problem or a power supply problem (not enough voltage/current).
- The first step to do is go to the Actuator window and check the Motor type that you have got selected, it should be "Rotatory Brushless AC (sinusoidal)". Make sure that you have the Position sensor and Velocity sensor properly configured as well according to your system. In the case of our example it was the following:
- Now you can use the Tune window and check in the Velocity tab that you are not able to reach the rated speed of your motor. In our case, we got the following velocity graph:
- As it can be seen, we clearly not reach the rated speed of the motor. In order to change that, we need to go back to the Actuator window and change the Motor type to "Rotatory Brushless DC (trapezoidal)":
- Now if we go back to the Tune window, we should be able to see that we can reach the rated speed of the motor: