There are three main excitation methods for DC motors: separately excited, shunt excited, and series excited. The characteristics and applications of these three excitation methods will be described in detail below.
I. Encouragement
Separate excitation, also known as external excitation, refers to a DC motor where the excitation power supply is separate from the armature power supply, and the excitation current is provided externally. Separate excitation has the following characteristics:
1.1 Excitation current and armature current are independent: In separately excited mode, the excitation current and armature current are independent, and the excitation current can be adjusted as needed to change the magnetic field strength of the motor.
1.2 Wide speed range: Since the excitation current can be adjusted independently, separately excited DC motors have a wide speed range and can achieve stepless speed regulation.
1.3 High starting torque: Separately excited DC motors can provide a large starting torque during startup, making them suitable for applications requiring high starting torque.
1.4 Low power factor: Since the excitation current is independent of the armature current, the power factor of separately excited DC motors is low, requiring a large excitation current to generate the required magnetic field.
1.5 Application areas: Separately excited DC motors are widely used in applications requiring a wide speed range and high starting torque, such as rolling mills and cranes.
II. Encouragement
Shunt excitation, also known as self-excitation, refers to a DC motor where the excitation power supply is connected in parallel with the armature power supply, and the excitation current is provided by the armature current. Shunt excitation has the following characteristics:
2.1 The excitation current is related to the armature current: The excitation current of the shunt excitation mode is related to the armature current, and the excitation current changes with the change of the armature current.
2.2 Small speed regulation range: Since the excitation current is related to the armature current, when the armature current decreases, the excitation current will also decrease, resulting in a decrease in magnetic field strength and an increase in motor speed. Therefore, the speed regulation range of DC motors with shunt excitation is small.
2.3 Low starting torque: When a shunt-wound DC motor starts, the excitation current is small and the magnetic field strength is low, so the starting torque is small.
2.4 High power factor: Since the excitation current is provided by the armature current, and the excitation current and the armature current are in phase, the DC motor with shunt excitation has a high power factor.
2.5 Application areas: Shunt-wound DC motors are widely used in applications where speed range requirements are not high and starting torque requirements are low, such as small DC motors and household appliances.
III. Series Excitation
Series excitation, also known as combined excitation, refers to a DC motor where the excitation power supply and armature power supply are connected in series, and the excitation current and armature current are the same. Series excitation has the following characteristics:
3.1 Excitation current is the same as armature current: In series excitation, the excitation current is the same as armature current, and the excitation current changes with the armature current.
3.2 Good speed regulation performance: When the armature current of a series-wound DC motor changes, the excitation current also changes accordingly, thereby changing the magnetic field strength and achieving speed regulation.
3.3 Larger starting torque: When a series-wound DC motor starts, the excitation current is large and the magnetic field strength is high, so the starting torque is large.
3.4 High power factor: Since the excitation current and the armature current are the same and in phase, the DC motor with series excitation has a high power factor.
3.5 Application areas: Series-wound DC motors are widely used in applications requiring good speed regulation and high starting torque, such as electric vehicles and power tools.
Summarize:
There are three main excitation methods for DC motors: separately excited, shunt excited, and series excited. Separately excited motors have a wide speed range and high starting torque, but a lower power factor. Shunt excited motors have a high power factor but a narrow speed range, making them suitable for applications where speed range requirements are not high. Series excited motors have good speed regulation performance and high starting torque, making them suitable for applications requiring both. The choice of excitation method for a DC motor should be based on specific application requirements and performance specifications.
