Brushless motors controller

This is a work in progress page on brushlless controller. The world is now moving from brushed to brashless motors. Many things are running and is an old story. You have to go back to alternators and to synchronous and asynchronous AC motors.

By the way we still have two engines configurations: male and female !!!



Male motor

When the controller connects two cables with + and - polarity, two windings are activate one that pulls and one that pushes the rotor. It depends on the position of the rotor if it will be moved clockwise or counterclockwise. Because of this is not easy to synchronize the controller. To synchronize, you must have the rotor in between the pushing and pulling windings when apply power. If the rotor is before the pushing winding it is pushed backward. Being the power driving synchronous, obviously, the rotor position depends on the engine load. So the only way to sync the current is the use of a position sensor.

Female motor

The triangle (female) configuration is a bit more complicate. It is normal to use the same controller of the Y configuration but this is not right. In triangle configuration, when we connect + and - to a couple of cable we have two engines internal connections in parallel that gives a higher current sunk from the battery. When battery is connected we have: one winding with current flowing clockwise, the other two with half current flowing counterclockwise. The force applied to rotor decreases like the square of the distance between rotor and windings so, there is no increase of torque apply current to far windings.

Male/Femal controllers

It is normally used the same controller for both the engines configurations. The main drawback consist of the using two mosfets to drive one cable. If the transistors are both closed because of a controller malfunctioning or failure you have a short circuit and every thing can brake. If you have lipo battery they are used to explode and destroy everything.

Normal motor and controller

This is a normal 3-phase motor, with all the internal connections accessible. It allows to eventually choose the internal windings configuration required by the controller. It is possible to semplify it unsing only 4 wires.


Controller considerations

The best option to drive the motor consist of independently driving the three windings. We have to apply current to one of them to push the rotor. If we apply reverse current we pull the rotor.
In this way we can have each of the three windings activated, one after the other, to synchronously rotate the rotor.
If we need more torque, we must push from one winding and pull from the next one.
If we need hence more torque, we can push one winding and pull from the two next windings.
To allow any option, we need three complete H-bridge to drive the winding.
It can work without synchronization but is better to use a single sensor to detect the position of rotor respect to one winding. The positions, to apply power to other windings, are recognizable simply dividing by three the rotation duration.
It is not simple, but is possible, to detect the position testing the back fem. To do it we have to check it when we do not apply power to the detecting winding.

Here following, you can find two controller projects under development :
  1. A sophisticated twin motor controller
  2. A thre phase four wires controller
To go back to PWM Controller Click here .

© 2013 - Alessandro Malanca

Motors control board

Here is the main one of the 3 boards that composes the controller.


Single motor board


Engine load driver




Twin brushless PCB



Single 3 phases 4 wires brushless controller

This is a single motor board to drive 4 wires 3 phases motors. It requires to open the motor and rewires it as apper in the schema.
It sense the fem on one inductor but can work without it too.

Schema

PCB

© 2015 - Alessandro Malanca