How to REVERSE THE ROTATION OF A THREE-PHASE MOTOR | Clockwise and counter-clockwise rotation

Summary

This video explains how to reverse the rotation of a three-phase motor by swapping two of the motor’s phases. It outlines the necessary control and power circuits, including components like thermal switches, start/stop buttons, and contactors. The video emphasizes safety measures such as interlocking contactors to prevent simultaneous activation. A simulation of the circuit is demonstrated using the Cade Seu software before moving on to real-world wiring. Clear instructions are given for both clockwise and counterclockwise rotation, along with wiring diagrams to guide users through the setup of the motor reversal system.

Takeaways

• 😀 Reversing the rotation of a three-phase motor can be achieved by swapping two of the three phases feeding the motor.
• 😀 The rotation direction is determined by the order of the phases; switching two phases reverses the rotation.
• 😀 The control circuit requires a bipolar thermal magnetic switch, stop and start buttons, and contactors for proper rotation control.
• 😀 Pressing the start button energizes the first contactor (KM1), making the motor rotate in one direction (clockwise).
• 😀 Pressing the stop button de-energizes the motor, stopping it from rotating.
• 😀 Pressing a second start button energizes the second contactor (KM2), reversing the motor's rotation (counterclockwise).
• 😀 Interlocking contactors (KM1 and KM2) ensure that only one contactor is energized at a time, preventing a short circuit.
• 😀 The power circuit involves reversing phases L1 and L3 using contactors to change the rotation direction safely.
• 😀 Proper safety measures include using motor protection switches and grounding cables to protect the system and components.
• 😀 Wiring the control circuit involves connecting stop/start buttons, contactors, and safety devices to ensure correct motor operation.
• 😀 For motors with multiple connection points, it's essential to configure the wiring in either star or Delta configurations, depending on the motor type.

Q & A

What is the basic method for reversing the rotation of a three-phase motor?

The basic method for reversing the rotation of a three-phase motor is by changing the order of the phases that feed the motor. Specifically, two of the three phases need to be swapped. For example, if the original order is L1, L2, and L3, swapping L1 and L3 will reverse the motor's rotation.

Why does changing the order of the phases reverse the motor's rotation?

The direction of the rotating magnetic field inside the motor depends on the order in which the phases are connected. By exchanging two of the three phases, the direction of the magnetic field is reversed, causing the motor to rotate in the opposite direction.

What components are needed for the control diagram of reversing the motor’s rotation?

For the control diagram, a bipolar thermal magnetic switch, a normally closed stop button, and two normally opened start buttons are required.

What components are necessary for the force diagram in motor rotation reversal?

For the force diagram, a motor protection switch and two contactors are necessary to perform phase switching and rotation reversal.

What is the function of the contactors in the power circuit?

The contactors are used to perform phase switching and rotation reversal. They control the direction of power flow to the motor by either energizing or de-energizing the phases connected to the motor.

How does the interlocking system between the contactors work?

The interlocking system uses normally closed auxiliary contacts on the contactors to prevent both contactors from being energized at the same time. This ensures that the rotation change is gradual and avoids short circuits or abrupt changes in motor rotation.

Why is it important to press the stop button before reversing the motor's rotation?

Pressing the stop button is necessary to de-energize the motor first, ensuring that the two contactors cannot be energized simultaneously. This step prevents short circuits and ensures the motor is safely switched to the opposite rotation.

How is the self-locking of the contactors achieved in the circuit?

Self-locking is achieved by connecting the auxiliary contacts of each contactor to its own coil. This allows the contactor to remain energized even after the start button is released, maintaining the motor's rotation until the stop button is pressed.

How are the start and stop buttons wired in the control circuit?

The start and stop buttons are wired in series. The stop button is normally closed, and the start button is normally open. The wiring connects to the auxiliary contacts of the contactors for self-locking and interlocking, controlling the motor's rotation direction.

What safety considerations must be made when wiring the control circuit for rotation reversal?

Safety considerations include ensuring the interlocking between contactors to prevent both from being activated simultaneously, which could cause a short circuit. Additionally, the motor should be de-energized before reversing its rotation to avoid sudden changes and potential damage.