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Reasons for The Volvo Generators Lack of Excitation

Jul. 23, 2021

To find and deal with the failure of Volvo generator set excitation system, it is to do an open loop characteristic test on Volvo generator set excitation voltage regulator. Before the test, disconnect the Volvo generator set rotor side DC switch and anode switch, connect the 380V power supply to the AC side of the controllable brick rectifier bridge through the auto-coupling voltage regulator, and connect the SCR DC side to the appropriate resistance load RL. Use an oscilloscope to observe the output voltage waveform of the thyristor DC side of Volvo generator set. When the analog terminal voltage changes between 70% and 110% UFN, the DC output voltage is continuously adjustable, the waveform is symmetrical, and every point can run stably. It indicates that the excitation voltage regulator is working normally. The secondary voltage of the Volvo generator set excitation transformer is similar to the voltage measurement input voltage, so one voltage regulator is used, otherwise two auto-voltage regulators must be used.

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After the wiring is completed, the test is performed, switch K is turned on, and the Volvo generator set auto-voltage regulator is boosted. At the same time, a clamp ammeter is used to monitor the primary current of the Volvo generator set regulator. As a result, the voltage regulator is seriously overheated and the normal test cannot be performed. When the Volvo generator set voltage regulator is boosted to 40V, the controllable silicon does not conduct, and the voltage regulator DC circuit does not work. The Volvo generator set voltage regulator only has a three-phase thyristor AC circuit. The primary current is too large, indicating that it can There is a problem with the thyristor AC circuit as the load of the Volvo generator set voltage regulator. Analysis and judgment are likely to be that the common side of the three diodes is grounded, and the rectifier bridge forms a zero-type rectifier, which makes the Volvo generator set voltage regulator load extremely small, resulting in a primary current Increase. The common side of the diode in the rectifier bridge is grounded to form a zero-type rectification, which makes the secondary load of the voltage regulator extremely small, which causes the primary current of the Volvo generator set to increase, the grounding is eliminated, and the loop returns to normal.


The wiring is ready for an open-loop test. Before the test, because there are other Volvo generator sets that need to be adjusted, switch K is turned off. After a while, the voltage regulator is found to be smoke, and the main power switch of the Volvo generator set is quickly turned off. A comprehensive inspection of the auto-voltage regulator revealed that phase A of the regulator was burned out. The power switch K was turned off before the voltage regulator of the Volvo generator set burned out. At this time, it is judged that there may be a problem with the power switch. Clean the dust on the thyristor and diode of the Volvo generator set, reinstall the thyristor and diode, use 500V to shake the meter to insulate the phase A, and the phase A insulation is normal. Replace the power switch K again, and then connect the wiring to test, boost the voltage regulator, and use a clamp ammeter to monitor the primary current of the Volvo generator set. The three-phase current is normal and the three-phase is balanced.


Firstly, it is judged that there is a problem with the diesel generator set automatic voltage given potentiometer RPA. The RPA is driven by a servo motor, and the increase and decrease magnetic buttons are operated. The servo motor rotates to drive the RPA to rotate, thereby changing the output of the Volvo generator set regulator pulse phase to control the The size of the thyristor conduction angle. The output waveform is not adjustable, it is likely that there is a problem with the RPA. Remove the RPA external line for measurement. It is found that the PRA resistance is not adjustable. Replace the potentiometer. Re-test, operate the increase and decrease magnetic buttons, the output waveform is still not adjustable, use the test plug-in board to connect the measurement and comparison amplifier unit board, use a multimeter to measure the voltage of UF, UG, UC, UR transistor VT1 under welding measurement, V15, VT1 are all Normal, re-welding and then observe the output waveform of the Volvo generator set regulator. When the analog machine voltage changes between 70% and 110%, the DC output voltage is continuously adjustable and the waveform is symmetrical.


Starlight Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, welcome send email to sales@dieselgeneratortech.com we will pay highly attention on your question.

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