The Operating Principles Of Brushed And Brushless Generators

Hello everyone, don't we often hear diesel generator suppliers recommend two types: brushed generators and brushless generators? So, what exactly is the difference between the two? What is their working principle? Today, this content will explain it to you clearly, so that even those with no prior knowledge can understand.

 

 

Ⅰ. Brushed Generator (Brushed Excitation)

Core: Carbon brushes and slip rings, mechanical contact for supplying excitation current.

 

1. Excitation power supply: The AVR (Automatic Voltage Regulator) sends DC current through the carbon brushes → slip rings into the rotor excitation winding, generating a magnetic field in the rotor.

 

2. Mechanical energy → Magnetic energy: The prime mover (diesel engine/gasoline engine) drives the rotor to rotate, forming a rotating magnetic field.

 

 

3. Magnetic energy → Electrical energy: The rotating magnetic field cuts through the stator's three-phase windings, and electromagnetic induction generates three-phase alternating current, which is output to the load.

 

4. Voltage stabilization: The AVR adjusts the excitation current according to the output voltage, stabilizing the magnetic field strength and maintaining a constant output voltage.

 

 

Key points: The excitation winding is on the rotor and is conducted via carbon brushes and slip rings; the structure is simple and low-cost, but the carbon brushes are prone to wear, produce sparks, and require regular maintenance.

 

Ⅱ. Brushless Generator (Brushless Excitation)

 

Core: Carbon brushless slip ring, using an exciter and rotating rectifier for excitation.

The main generator and exciter are separate machines, co-axially rotating with no mechanical contact.

 

1. Initial excitation: The rotor's residual magnetism induces a tiny residual voltage in the main generator stator, and the AVR starts working.

 

2. Exciter generates power: The AVR sends DC to the exciter's stator windings to create a constant magnetic field; the exciter rotor (co-axial) cuts through the magnetic field, producing medium-frequency AC.

 

3. Rotating rectification: The alternating current from the excitation generator rotor is converted into direct current through a coaxial rotating rectifier (diode) and directly supplied to the main generator rotor excitation winding (brushless).

 

4. Main generator electricity generation: The main generator rotor produces a strong rotating magnetic field, which cuts through the main generator stator winding and induces a stable three-phase alternating current output.

 

5. Closed-loop voltage regulation: The AVR monitors the output voltage in real time and dynamically adjusts the stator current of the exciter to stabilize the main generator voltage.

 

Key points: Eliminates carbon brush slip rings, resulting in no wear, no sparks, minimal interference, and maintenance-free operation; the structure is slightly complex and cost is somewhat higher, making it suitable for long-term continuous operation (such as in power plants and ships).

 

Let's highlight the key points here for everyone:

✅ Brushed generator: conducts electricity through friction contact between carbon brushes and the slip ring. Simple structure, but the carbon brushes wear out easily and need regular replacement.

✅ Brushless generator: conducts electricity without contact through electromagnetic induction. No easily worn parts, lower failure rate, and longer lifespan.

 

Now you can tell the working principles of the two types of generators apart! If you found this useful, give it a like, save it, and share in the comments which type of generator you've used!