What Causes a Generator Under Voltage

A generator is a mechanical device that converts other forms of energy into electrical energy. It is driven by a water turbine, a steam turbine, a diesel engine or other power machinery, and converts the energy generated by water flow, airflow, fuel combustion or nuclear fission into mechanical energy and transmits it to the generator. Converted to electricity by a generator. Generators are widely used in industrial and agricultural production, national defense, science and technology and daily life.

There are many forms of generators, but their working principles are based on the law of electromagnetic induction and the law of electromagnetic force. Therefore, the general principle of its construction is: use appropriate magnetic and conductive materials to form magnetic circuits and circuits that conduct electromagnetic induction with each other to generate electromagnetic power and achieve the purpose of energy conversion.

What causes the generator under voltage?

(1) The speed of the prime mover is too low.

(2) The resistance of the excitation circuit is too large

(3) The exciter brush is not at the neutral position, or the spring pressure is too small.

(4) Some rectifier diodes are broken down.

(5) There is a short circuit or ground fault in the stator winding or the excitation winding.

(6) The contact surface of the brush is too small, the pressure is insufficient, and the contact is poor. If it is caused by the surface of the commutator, you can polish the surface of the commutator with emery cloth at low speed, or adjust the spring pressure.

For the above reasons, how to increase the generator voltage?

1. Adjust the speed of the prime mover to the rated value.

2. Reduce the resistance of the magnetic field rheostat to increase the excitation current. For semiconductor excitation generators, check whether the additional winding joints are disconnected or wrongly connected.

3. Adjust the brush to the correct position, replace the brush, adjust the spring pressure.

4. Check and replace the breakdown diode.

5. Check the fault and remove it.

Other ways to increase generator voltage:

Increase the excitation weight of the generator;

increase the speed of the generator;

Reduce the resistance of the circuit in the generator;

Lightening of the load or the amount of excitation increases as the load increases.

How to keep the generator terminal voltage unchanged

When the load current of the generator changes, according to the external characteristic curve, the terminal voltage of the generator will change with it.

In order to keep the terminal voltage of the generator constant, the excitation current of the generator must be adjusted accordingly.

Under the condition of keeping the speed, load power factor and terminal voltage unchanged, the relationship between the excitation current IL and the load ls is called the regulation characteristic of the generator.

For purely resistive and inductive loads, as the load current increases, the terminal voltage of the generator will gradually decrease. In order to keep the terminal voltage unchanged, the excitation current must be increased accordingly to compensate for the demagnetization and leakage reactance of the armature reaction. pressure drop.

For capacitive loads, since the terminal voltage of the generator will increase with the increase of the load current, the excitation current must be reduced to offset the excitation effect of the armature reaction and the boosting effect of the leakage reactance, so as to maintain the terminal voltage. constant.

Problems that should be paid attention to when paralleling a no-load generator with the power grid: at the moment of switching on and closing, the generator should not have harmful inrush current, and the rotating shaft should not be subjected to sudden shock.

After closing, the rotor should be able to be pulled into synchronization quickly (that is, the rotor speed is equal to the rated speed). For this reason, the synchronous generator must meet the following conditions:

1. The effective value of the generator voltage should be equal to the effective value of the grid voltage.

2. The phase of the generator voltage and the phase of the grid voltage should be the same.

3. The frequency of the generator is equal to the frequency of the grid.

4. The phase sequence of the generator voltage is consistent with the phase sequence of the grid voltage.

5. It is strictly forbidden to send electricity back to the power grid.