Detailed Operation Process for Manually Exciting Diesel Generators (By Model, Safety First)

 

Preliminary Safety Instructions

 

1. During the operation, the generator set should be unloaded, with both the main output switch and the load switch turned off. Do not magnetize while under load.

 

2. Keep your hands dry and avoid touching the metallic parts of the terminals to prevent electric shock.

 

3. Use a 12V/24V car battery (preferably 12V; suitable for household/small generator sets) and choose slightly thicker copper wires.

 

4. Magnetization should only last 2~5 seconds at a time; do not connect for a long time to avoid damaging components.

 

 

I. Self-excited Brushless Generator (Most small/medium generator sets on the market, most commonly used)

 

1. Locate the magnetization terminals

 

Open the generator control box/rear cover, find the voltage regulator (AVR), and identify two sets of terminals:

 

- Excitation input terminals: usually labeled F, F-/EXC, EXC-/Excitation, Excitation-

 

- Identify positive and negative: the terminals have +, - labels; connect the red wire to + and the black wire to -

 

2. Operating steps

 

1. Start the diesel engine and stabilize it at the rated speed (frequency meter 50Hz, speed 1500 r/min).

 

2. Quickly touch the battery positive (red wire) to F, and the battery negative (black wire) to F-; disconnect immediately after 2~3 seconds.

 

3. Observe the voltmeter: it should briefly rise to the rated voltage (220V/380V), completing the magnetization.

 

4. Stop the machine, organize the wiring, then close the breaker and test under load.

 

Supplement: No separate F terminal (integrated AVR)

 

Directly operate on the excitation plug outside the AVR, also distinguish positive and negative, and touch briefly.

 

II. Brush Generator (with brushes, slip ring type)

 

1. Locate the two brush leads at the rear of the generator; these are the positive and negative excitation leads.

 

2. Run the diesel engine at rated speed, connect the battery positive and negative to the two brush leads correspondingly, and disconnect after 2~5 seconds.

 

3. Once the voltage is established, the operation is complete.

 

III. Two emergency methods (when labels are missing)

 

Method 1: Trial connection (to prevent reverse polarity)

Touch lightly first; if the voltage doesn't change, the polarity is reversed. Swap the two wires and try again.

Reversing polarity generally does not damage components, but the generator will not build voltage; no need to worry.

 

Method 2: Terminal magnetization (for old generator sets)

Find the generator's single-phase 220V output terminal, briefly bridge the battery across the output (only for old models, not recommended for new sets), and disconnect after 2~3 seconds.

 

IV. Common Problems & Remedies

 

1. Magnetization ineffective the first time

Power off for 10 seconds, then repeat the magnetization 2~3 times; check if the speed is too low or the wiring is not making proper contact.

 

2. Magnetization successful, but lost after shutting down and restarting

The winding is severely demagnetized or AVR rectifier elements are deteriorated; AVR and rectifier bridge need servicing.

 

3. Trips breaker/smoke immediately upon magnetization

Stop operation immediately; this indicates a short circuit in the winding or wiring. Do not attempt forced magnetization; arrange for repair.