How is electromagnetic torque generated?

Electromagnetic torque refers to the torque generated by the interaction between the magnetic field generated by the current in the motor and the magnetic poles in the magnetic field. For AC motors, since the principle is relatively complicated, the following briefly introduces the process of generating electromagnetic torque in DC motors.

In a DC motor, electromagnetic torque is generated by the interaction between the current in the coil and the magnetic field. As the coil of the DC motor passes the current provided by the power supply during operation, a magnetic field is generated around the coil. There is polarity in the magnetic field and it interacts with the polarity in the magnet. When the rotor of the motor starts to rotate, the magnetic poles also rotate, thereby intermittently interacting with the surrounding magnetic field to generate a changing torque force, namely electromagnetic torque.

More specifically, when the motor power supply applies voltage, the electrons in the conductor are deflected by the electric field and generate current. In a DC motor, the direction of the current in the conductor is controlled by a switch. The magnetic field generated by the conductor current interacts with the magnetic field generated by the electrode to generate torque. Every time the rotor rotates a certain angle, the magnetic field between the positive and negative poles will change accordingly, and the direction of the electromagnetic torque will also change. If the magnetic field is strong enough and the alternating speed is fast enough, a stable torque can be formed to drive the motor to rotate in a certain direction.

In short, electromagnetic torque is the basis of DC motor operation. The important factors that generate electromagnetic torque include the current intensity and magnetic field intensity in the wire, the structure and layout of the coil, the shape and material of the rotor, etc. Only under the combined effect of these factors can the motor generate sufficient torque and achieve efficient and stable working state.

The method of generating electromagnetic torque is that the armature winding of the generator cuts the magnetic lines of force to induce electric potential and emit current under the drive of the prime mover; when the current flows through the armature winding, this current will be affected by the magnetic field to generate electromagnetic force in the magnetic field, and form electromagnetic torque. This torque is opposite to the direction of the prime mover torque, and its magnitude is proportional to the output current. The prime mover torque overcomes the electromagnetic torque to keep the generator rotating at a constant speed, thereby converting mechanical energy into electrical energy and transmitting it.

Without considering efficiency, it can be considered that the output load of the generator is the output current. The increase of external load means the increase of current, which is reflected in the increase of electromagnetic torque of the generator. The load torque of the motor driving the generator will also increase, which is the energy conversion. Considering efficiency and mechanical loss, the load torque of the motor should be slightly greater than the electromagnetic torque of the generator.