Are you facing any issues with your generators? Here are some Methods to troubleshoot the power failure in the generator.
A generator is a device that converts mechanical energy into electrical energy for use in an external circuit. At present, generators are widely used in offshore oil and gas, construction, events, telecoms, manufacturing industry, agriculture, national defense, science & technology, etc.
How does a generator work?
A generator works by moving electrical conductors through a magnetic field. If your generator doesn’t have magnets, it won’t produce electricity. The magnetic field is created by taking some of the generator output voltage and converting it to DC and feeding it to a coil to make an electromagnet.
Nowadays, the generator degree of automation is high, the control circuit is also complex, thus, some faults may occur when the generator set is at work, which directly affects the normal power supply operation of the unit. So, during the normal operation of the Genset, except for monitoring and analyzing the data on the system instrument, it is also necessary to observe whether the parameters of the generator on each instrument are within the normal range or not.
Why won’t a generator produce electricity?
This is a hot topic that many users care about, I will analyze the reasons for you.
After the unit is running, the generator rotational speed reaches the rated speed, the AC exciter stator excitation circuit switch is closed, the voltage regulator is raised to the maximum direction, at this time, the generator has no output voltage, or the voltage is very low. That’s why a generator fails to produce electricity.
Why does such failure occur?
1. The residual magnetism of the generator core is disappeared or is too weak.
The residual magnetism can be lost naturally when the Genset is placed too long, or it can also happen from running a generator with no load for too long. However, for the new Genset, the residual magnetism can be lost due to a long-distance transportation vibration.
Thus, it will cause the remanence voltage of the generator is disappeared or be less than the normal remanence voltage value, namely, the remanence line voltage is less than 10V, the remanence phase voltage is less than 6V. Because the stator of synchronous generator, rotor, as well as AC exciter stator, and rotor core are usually folded by adopting 1~1.5mm thick silicon steel sheet.
After excitation vibration, the residual magnetism is easy to disappear or weaken. When the residual magnetism is lost, the generator will produce no power at the start-up.
2. Excitation circuit wiring error
The polarity of the excitation winding is reversed. After electrifying, the magnetic field produced by the field winding current is counteracted with the residual magnetism, resulting in the disappearance of the remanence. In addition, when measuring the DC resistance of the excitation winding or testing the automatic voltage regulator AVR, without paying attention to the polarity, which will also cause the core remanence to disappear.
3. Excitation circuit is blocked
In the generator excitation circuit, the electrical contact is bad, or the wiring head of each electrical component is loose, the lead wire is broken, causing the circuit to be interrupted, and the generator excitation winding has no excitation current.
4. Circuit for DC side of rotary rectifier is interrupted
Due to the interruption of a circuit for the DC side of the rotary rectifier, therefore, after the AC exciter is rectified by the rotary rectifier, the excitation current supplied to the excitation winding cannot be sent into the excitation winding, resulting in AC synchronous generator cannot generate electricity.
5. AC exciter fault, no output voltage
The generator can’t produce electricity due to AC exciter failure so the excitation winding of the AC synchronous generator has no excitation current.
6. Generator excitation winding is broken or grounded
Generator excitation winding is broken or grounded, resulting in the generator having no excitation current or the excitation current being minimal.
How to solve it?
1. When the residual magnetism of the generator core disappears, magnetizing treatment shall be carried out.
The magnetizing method for the self-excited generator, usually using an extra battery or dry battery, uses its positive and negative poles to supply electricity for a short time towards the leading-out terminal of the excitation winding.
However, be sure to recognize the polarity of DC power supply and excitation winding clearly, namely, the positive pole of the DC power supply is connected to the positive pole of the excitation winding, and the negative pole of the DC power supply is connected to the negative pole of the excitation winding.
If the control panel of the diesel generator set is equipped with a magnetizing circuit, the toggle switch should be turned to a “magnetizing” position, which can magnetize the AC exciter.
2. Excitation circuit wiring error, correct it after searching.
3. Use a multi-meter ohm block to find the excitation winding broken line and connect it.
For the failure caused by poor contact, polish the surface oxide layer with fine sand cloth, the loose connection bolt and nut shall be firm.
4. Ground and broken line fault of excitation winding
Use 500V ohmmeter to check the ground insulation of the excitation winding, find out the ground point, use a multi-meter to find out the broken line, and restore it.
Hope the above methods can help you restore your generator output power. If it still fails. you need to replace the automatic voltage regulator as it may be damaged.