Three phase motor forward and reverse circuit with Latch ON || Chain Hoist basic understanding

Summary

This tutorial explains how to wire a three-phase motor to run in both forward and reverse directions using contactors, auxiliary contacts, push buttons, and a motor protector breaker. It demonstrates the importance of proper interlocking to avoid short circuits, how to switch motor phases for reverse operation, and the function of control and power wiring. The video guides viewers step by step through the wiring process, explaining the role of each component in ensuring the motor operates safely and efficiently. Perfect for anyone looking to understand three-phase motor control in workshops or industrial settings.

Takeaways

• 😀 Two three-phase contactors are required: one for forward direction and one for reverse direction.
• 😀 The contactors must be interlocked using auxiliary contact blocks to prevent short circuits by ensuring only one contactor is on at any time.
• 😀 A motor protector breaker is essential to protect the motor from overloads by cutting off power if the motor draws excessive current.
• 😀 Green push buttons (normally open) control the forward and reverse contactors for motor direction control.
• 😀 The red push button (normally closed) is used to stop the motor by cutting the power to the contactor coils.
• 😀 Phases must be swapped on the reverse contactor to change the motor’s direction.
• 😀 The wiring setup includes neutral and control phase wires, jumpers, and push buttons to properly operate the system.
• 😀 The forward and reverse contactors are connected to the motor's output terminals, with jumper wires linking the contactors.
• 😀 Interlocking ensures that the reverse contactor’s normal close contact prevents the forward contactor from turning on while the reverse contactor is active.
• 😀 To latch the contactors, a phase wire is connected from the output of the red stop push button to the normal open contact of each contactor, ensuring they stay on after being pressed.
• 😀 The motor direction is controlled by pressing the green forward or reverse push buttons, and the red stop button is used to turn off the motor.

Q & A

What is the purpose of a chain block or chain hoist?

A chain block or chain hoist is used in workshops to safely lift heavy loads using a three-phase electric motor coupled with a gearbox.

How is a three-phase motor operated in the forward and reverse directions?

A three-phase motor is operated using two contactors, one for the forward direction and another for the reverse direction. The direction is controlled by switching the positions of two phases.

What is the function of auxiliary contact blocks in this setup?

Auxiliary contact blocks are used to interlock the forward and reverse contactors, ensuring that only one contactor is active at a time to prevent short circuits.

What role does the motor protector breaker serve in the circuit?

The motor protector breaker trips and turns off the contactors if the motor is overloaded and draws more current than its rated capacity, preventing damage to the motor windings.

What are the green and red push buttons used for in the system?

The green push buttons are used to turn on the forward or reverse contactors, while the red push button is used to stop the motor by turning off the contactors.

How are the power wiring and control wiring connected in this setup?

Power wiring is connected from the motor protector to the forward and reverse contactors, and control wiring connects the push buttons and contactors to control the motor direction and operation.

What happens when both forward and reverse contactors are switched on simultaneously?

If both contactors are on at the same time, it would create a short circuit and potentially damage the contactors, which is why they are interlocked to prevent this situation.

How is the forward contactor interlocked with the reverse contactor?

The forward contactor is interlocked with the reverse contactor using a normal close (NC) auxiliary contact. This ensures that the forward contactor can only turn on when the reverse contactor is off.

What is the purpose of the latch or hold-on mechanism for the contactors?

The latch or hold-on mechanism ensures that the contactors remain engaged after pressing the respective green push button, keeping the motor running until the red stop button is pressed.

How does the motor change direction when switching between forward and reverse?

The motor direction is changed by swapping the connections of two phases (e.g., L1 and L3), which reverses the current flow and causes the motor to run in the opposite direction.