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BRUSHED VS BRUSHLESS DC MOTOR: AN OVERVIEW

BRUSHED VS BRUSHLESS DC MOTOR: AN OVERVIEW

Brushed DC Motor

A brushed DC motor is one of the simplest types of motors. It consists of a few main components which in conjunction with a DC power supply create a rotating motor. The armature, commutator, brushes, and field magnet configuration can be seen in Figure 1 below.

Brushless Fig 1 Figure 1

 

The brushes charge the commutator which delivers current through the armature in the opposite polarity of the permanent magnet. This causes the armature to rotate from the attraction of the magnets.

Due to the brushes making physical contact with the commutator, sparking is a common issue with brushed motors. These motors are not recommended for long term use as the brushes wear out over time.

Brushless DC Motor Controller

A brushless DC motor (BLDC) eliminates the major inefficiencies of its brushed counterpart. The motor is comprised of permanent magnets and coils, which through a series of perfectly timed energizing intervals cause the permanent magnet to rotate around the coils. See Figure 2 below for a detailed view of a brushless motor.

Brushless Fig 2 Figure 2

 

The coils in the brushless motor are energized in a specific sequence (Figure 3), which causes the permanent magnets on the rotor to rotate. This is done without any physical contact and allows for a more efficient, longer lasting DC motor.

Brushless Fig 3 Figure 3

 

To follow the output shown in Figure 3, the brushless DC motor requires an Electronic Controller Unit (ECU), to determine the position of the rotor and which coils to energize. A Hall Effect is a common sensor inside most brushless motors.

Unlike the brushed DC motors which requires 12VDC applied directly across the motor to rotate, the brushless DC motor requires 3 phase power. This means that a Brushless DC Motor controller must output the appropriate power to the motor to move it. Using the LC-241, 12VDC and 5A can be applied to the input terminals of the controller. This is then converted to 3 phase power to control the brushless motor. In the next section, a basic wiring diagram will assist in testing a brushless DC actuator.

Wiring Diagram/ Basic Set Up

Progressive Automations currently offers the PA-14 Mini Linear Actuator in the Brushless DC option, this unit will be used for the demonstration below. Figure 4 details a basic wiring schematic:

wirediagram

Step 1: Connect the 3 motor controller wires from the PA-14 Brushless Actuator to the LC-241 Brushless DC Motor Controller; typically the wires are green, blue, and white, which will connect to the U, V, and W terminals respectively. If the wires are different colors, connecting them in the wrong order will simply move the electric linear actuator in the opposite direction than intended.

Step 2: Connect the SPD pin to Ground, this will engage the built in potentiometer for speed control and ensure that this potentiometer is rotated clockwise for full speed.

Step 3: Connect the GND pin to the Common pins on the rocker switch.

Step 4: Connect the RUN pin to both sides of the rocker switch, this is important as both forward and reverse need the RUN pin connected to Ground to function.

Step 5: Connect the REV pin to one side of the rocker switch, this side will be the reverse direction side of the rocker switch.

Step 6: Apply 12VDC to the brushless DC motor controller, an indicator noise can be heard on initial power up.

Brushless Fig 5 Figure 5

 

The basic set up is now complete; using the rocker switch, the actuator can be extended and retracted. The issue with a brushless DC motor actuator is that the internal limit switches are not able to stop the power to the actuator. This is because the power going into the PA-14 Brushless Motor is 3 phase power. The PA-14 Brushless electric actuator comes with built in limit switch feedback which can be utilized with a PLC controller to indicate that the actuator is at end of travel. The feedback acts as a Normally Closed to Normally Open switch which is essential to integrating a PA-14 Brushless Actuator into real-world applications.

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