What is meant by active and reactive power?
A: In the process of generating, transmitting and using AC electric energy, the part of energy used to convert into non-electrical and magnetic forms is called active power; the part of energy used for the exchange of electric and magnetic fields in the circuit is called reactive power.
Active power is also called average power. The instantaneous power of alternating current is not a constant value, the average value of power in a cycle is called active power, it refers to the power consumed in the resistive part of the circuit, for the motor is its output power, expressed by the letter P, the unit is kilowatt (KW). Reactive power: In a circuit with an inductor (or capacitor), the inductor (or capacitor) turns the energy of the power supply into the energy of the magnetic field (or electric field) in half a cycle of time and stores it, and returns the stored energy of the magnetic field (or electric field) to the power supply in another half a cycle of time. They only exchange energy with the power supply, and do not really consume energy. We call the amplitude value of the energy exchange with the power supply reactive power, expressed by the letter Q, the unit of kilowatt (kvar). Apparent power: In the circuit with resistance and reactance, the product of voltage and current is called apparent power, expressed by the letter S or the symbol P, the unit is kilovolt-ampere (KVA). The relationship between active power, reactive power and apparent power can be expressed by power triangle
What is the parallel engineering of generator sets?
Several generators in parallel is equivalent to a high-power generator to supply power to the load, you can decide how many machines to turn on according to the size of the load (the lowest fuel consumption rate under 75% of the rated load), so as to achieve the purpose of saving diesel fuel and reducing the cost of power generation; to achieve uninterrupted power supply, to protect the normal production of the factory, when the unit is converted to use, the standby unit can be integrated into the operating system, and then the load will all When the unit is switched to use, the standby unit can be integrated into the running system, and then the load can be transferred to the running standby unit, and then the original running unit can be stopped, so that there is no need for power failure in the middle of the process.
What is the reason for the diesel generator oil pump not supplying oil?
According to the exhaust temperature, pressure or smoke color of each cylinder to determine its actual working conditions and the degree of combustion of the diesel engine, so as to determine the cylinder oil supply too much or too little, oil supply time too early or too late, and then adjust. By properly adjusting the amount and time of oil supply to each cylinder, let the injection pump supply oil to each cylinder of the diesel engine in accordance with the principle of distribution according to demand, in order to eliminate the actual differences between the cylinders.
The main reasons for starting the diesel generator oil pump is not on the oil are as follows.
1. poor assembly or reversal of the oil pump.
2. the oil pump shell is not tight and into the air.
3. The oil drawing pipe system is not tight and produces air leakage.
4. The oil suction line is blocked.
5. The stuffing box of the oil pump is not tight.
6. The oil filter is blocked or the oil suction check valve is out of order.
7. The oil tank oil quantity is too low.
Removal methods: 1.
1. Check and repair the oil pump.
2. Clean and repair the oil filter, oil suction valve and oil suction pipeline.
3. Eliminate the tightness to avoid air leakage.
4. Discharge the air in the oil suction pipe and oil pump by filling oil.
5.Maintain a certain oil level in the oil tank.
What is the role of temperature sensor in diesel generator?
To ensure the proper operation of the diesel generator, the coolant temperature and fuel temperature inside the generator set need to be detected during operation, which requires the application of a temperature sensor.
In diesel generators, the coolant temperature sensor is located in the right front side of the cylinder, and its function is to control the fan rotation, adjust the starting fuel supply, control the injection timing and engine protection. A typical diesel generator operates in the range of -40 to 140°C. If the temperature sensor fails it will result in lower engine speed and power drop, difficult starting and the generator will shut down. Most of the coolant temperature sensors in diesel generators use thermistors.
The fuel temperature sensor in diesel generators is mounted on the top of the inner housing of the fuel filter. Its function is to control the fuel heater and protect the diesel generator by the temperature sensor signal. If the sensor fails, it will also affect the performance of the engine.
Why do generators start with excitation power?
Answer: In order to establish the initial voltage of the generator. First, add excitation to the rotor by starting the excitation power supply to form a rotor magnetic field. According to the principle of electromagnetic induction: the movement of a conductor in a magnetic field induces a current. When the rotor rotates, there will be current in the stator, and the motion is relative. If the rotating magnetic field is used as a reference, the stator is the so-called moving conductor! When the generator outlet voltage reaches the normal excitation voltage, the excitation power supply will automatically exit, and the excitation thyristor rectifier will automatically switch!
When there is no exciter but the excitation transformer, the start-up power supply should be used first, because the generator has no power at the beginning, and the excitation transformer has no power at the beginning, so first use the start-up power supply to give a little power and a little excitation. The current, and then after a little, the starter power supply was thrown off. The excitation power supply is very small, as long as you give it a little, the generator can generate electricity, and then the excitation transformer also has electricity, and the cycle starts. If the shutdown time is short, it can be started by residual magnetism, and generally does not need to start the excitation power supply, unless it is necessary for large and small repairs.
What is non-contemporaneous juxtaposition, and what is the harm of non-con temporaneous juxtaposition?
Synchronous generators are paralleled with the system when they do not meet the quasi-synchronous paralleling conditions, and we call them asynchronous paralleling.
Asynchronous juxtaposition is a serious accident in power plants, which is extremely destructive to related equipment such as generators and their series-connected transformers, switches, etc. In severe cases, the generator windings will be burnt and the ends will be seriously deformed. If the equipment is not damaged immediately, it may also cause serious hidden dangers. As far as the entire power system is concerned, if a large unit is paralleled asynchronously, it will have a great impact, possibly causing power oscillation between the generator and the system, seriously disrupting the normal operation of the entire system, and even causing collapse.
After the generator set starts normally, the voltage is high (three-phase 600V) and there is no voltage for about ten seconds?
Q : Is your connection correct?
A : Yes
Q : Is your No. 7 line connected to the zero line of the generator set?
A: Yes
Q : Is your No. 6/8 line connected to the L1 and L2 lines of the generator set?
A : Yes
Q : Then you can adjust the RMS potentiometer a little bit in reverse.
A : Adjust the RMS potentiometer, but the voltage (320V) has no voltage after about ten seconds.
Q: Then you: adjust the OVER V potentiometer (clockwise)
A : Adjust the OVER V potentiometer. If the voltage is high (three-phase 410V), it cannot be adjusted down, but it can be adjusted up.
Q : Does your unit have an adjustable resistor? It would be nice if you didn’t have one
What is the so-called reverse power transmission of the generator? What are the two serious consequences?
Answer: The situation that the self-provided generator sends electricity to the city network is called reverse electricity transmission. There are two serious consequences:
a) If there is no power failure in the city network, the power supply of the city network and the power supply of the self-provided generator will be paralleled asynchronously, which will destroy the unit. If the capacity of the self-provided generator is large, it will also cause shocks in the city network.
b) The city network has been out of power and is being repaired, and its self-provided generator sends electricity backwards. The maintenance personnel of the power supply department will be electrocuted.
What is the meaning of floating charge of generator charger？
Generator charger float charging and cell phone charger float charging principle of work is similar. Floating charge is a kind of battery pack supply (discharge) power work mode, the battery pack and power lines connected in parallel to the load circuit, its voltage is largely constant, only slightly higher than the battery pack break voltage, by the power lines supplied by a small amount of current to compensate for the loss of the battery pack local role, so that it can often be maintained in the charge to meet the state and not overcharge. Therefore, the battery can be charged and discharged with the fluctuation of the power line voltage. When the load is light and the power line voltage is high, the battery pack is charging, when the load is heavy or the power supply accidental interruption, the battery pack is discharging, sharing part or all of the load. In this way, the battery pack plays the role of voltage stabilization, and is in a standby state.
How to check the real useful power of diesel generators?
Answer: The method to determine the real useful power of the unit is: multiply the rated power of the diesel engine for 12 hours by 0.9 to obtain a data (kw). If
the rated power of the generator is less than or equal to the data, the rated power of the generator is determined as the real useful power of the unit. If the rated power of the generator is greater than this data, this data must be used as the real useful power of the unit
What harm does a short circuit do to the generator and system?
Answer: The harm of short circuit to generator:
(1) The end of the stator winding is subjected to a large electromagnetic force, which may break the outer insulation of the wire rod;
(2) The rotor shaft is subjected to a large electromagnetic torque;
(3) cause heating of the stator winding and rotor winding;
The effect of short circuit on the power system:
(1) It may cause damage to electrical equipment.
(2) The stable operation of the system may be destroyed due to low voltage.
What are the advantages and disadvantages of several methods of parallel generators?
Answer : There are two types of generator parallel methods: quasi-synchronization method and self-synchronization method.
1. The advantages of the quasi-contemporaneous method:
(1) The generator has no inrush current when closing;
(2) There is no impact on the power system.
2. Disadvantages of quasi-contemporaneous juxtaposition:
(1) If due to some reason, the inrush current is very large, even twice as large as the three-phase short-circuit current at the machine end;
(2) When manual quasi-synchronization is used, it is not easy for the operator to grasp the advance time of the parallel operation.
3. The advantages of self-concurrent juxtaposition:
(1) The operation method is relatively simple, and the automation of the closing process is also simple.
(2) In the event of an accident, closing quickly.
4. Disadvantages of juxtaposition since the same period:
(1) There is an inrush current, and it has an impact on the system;
(2)The voltage of the system decreases at the moment of closing.
How to diagnose and deal with the difficulty of engine hot start?
1、Diagnostic reasons
Mainly due to serious wear of the injection pump plunger and injector needle valve. When the car is hot to start, due to the high temperature of the injection pump and fuel filter, the fuel viscosity drops, coupled with the low starting speed, most of the diesel fuel leaks from the worn gap, resulting in insufficient starting oil and can not start.
2、 Diagnosis and treatment method
① The method of emergency exclusion is: put the car in gear and start by other cars towing. Use the speed of the car to drive the engine to rotate at high speed, so that the diesel fuel is too late to leak to ensure the starting oil supply (this method is not advocated, because the cylinder pressure of Cummins supercharged engine is relatively large, and the impact of the trailer starting on the connections is large, affecting the service life of the vehicle).
② If the plunger or needle valve is seriously worn, after the injection pump test bench inspection and debugging confirmation, should be replaced with new products.
Can the battery charger use the power from the generator to charge the battery?
Yes, battery chargers generally have automatic float charging and other functions, the generator set users can use the generator to send out the electricity directly to charge, and can ensure that the engine at low speed (idle speed) to work.
What conditions need to be met for the generator to be paralleled?
Answer: The conditions for parallel generators to meet (1) voltage are equal at the same time. (2) The voltage phase is the same. (3) The frequencies are equal. (4) The phase sequence is the same.
1. The voltage is equal means that the voltage of the generator and the system is close (generally the difference does not exceed 10% at most). If the voltage is not equal: the consequence is that after the juxtaposition, there will be a circulating current of reactive power between the generator and the system.
2. Consistent voltage phase means that the generator voltage phase angle is close to the system voltage phase angle (generally the difference is not more than 20 degrees). Of course, if the voltage phase is inconsistent, the consequence is that a large inrush current may be generated, causing the generator to burn out. , or the end is damaged by the action of huge electric power.
3. Equal frequency means that the generator frequency is close to the system frequency (generally the difference does not exceed 0.5HZ). Similarly, if the frequencies are not equal, the consequence is that a beat voltage and a beat current will be generated. The torque generated by the active component of the beat current on the generator shaft will cause the generator to produce mechanical vibration. When the frequency difference is large, even the generator cannot be synchronized after being merged.
4.The generator needs to be connected to the grid through the synchronization device, there are manual quasi-synchronization, and there are automatic quasi-synchronization. The generator voltage and frequency need to be adjusted to meet the grid connection conditions.
What is the reason for the high water temperature of the generator set?
Generator set water temperature is high, the phenomenon is very common, but there are many causes, first of all, look at the unit ventilation conditions up to standard, the second look at the load there is no super, three look at the thermostat return pipe plugged no, to plug, four look at the water tank outside there is no oil blocked, the fan belt is too loose, the most important is the internal blockage of the water tank. Secondly, whether the water pump is good, of course, when the oil nozzle atomization or valve leakage caused by high exhaust temperature, the water temperature is naturally high, but the chances of this is not large.
What is the relationship between the speed drop of the generator governor and the load distribution?
Multiple units in parallel, the transfer rate should be positive, of course, a backbone unit can also be close to zero. If they are all zero, each unit will have to grab the load and cannot operate stably. In fact, due to the existence of speed regulation dead zone of many units, the situation of load grabbing may not necessarily be very bad.
What is the maximum speed of the generator governor can be set?
Answer : The highest setting is: 1800 rpm, the overspeed value is: 1750 rpm, the normal value is: 1475-1575 is the normal range, the shutdown is free to set, and the maximum engine speed is limited by the oil pump . It can fully meet the requirements of high-speed generators.
What is the voltage of four 12V generator chargers connected together
A: It is still 12V (the float voltage is 13.7V), only the charging current has increased. If it is in series, it is U=4*12V=48V.
The engine idle speed is too high, how to diagnose and deal with it?
A : The idle speed of the engine is too high, which means that when the accelerator is lifted, the engine speed is still higher than the specified idle speed.
⑴ Reason
① The throttle lever is not adjusted properly.
② The accelerator return spring is too soft.
③ The idle speed limit stop or adjustment screw is out of balance.
④ The idle spring is too hard or the preload is adjusted too much.
(2) Diagnosis and treatment methods
High engine idle speed is one of the easiest faults to troubleshoot. First, check whether the throttle has returned to the minimum position. If not, check the throttle adjustment and throttle return. Adjust the throttle cable limit screw, if the throttle still cannot be returned, check whether the throttle return spring is too soft. If it is a fuel injection pump that has been repaired and debugged soon, it should be considered whether the idle speed adjustment is correct, and whether the idle speed spring preload adjustment is too large. If the spring has been replaced, check whether the spring is too hard.
What is the working principle of generator float charging?
Float charging principle of operation: when the battery is in a full state, the charger will not stop charging, will still provide a constant float charging voltage with a very small float charging current supply battery, because, once the charger stops charging, the battery will naturally release electrical energy, so the use of float charging to balance this natural discharge, generators or small UPS usually use the float charging mode.
If the generator is only magnetically regulated at 1500 rpm, can it be magnetized at 1200 rpm?
A : It is certainly possible in principle. If it cannot be adjusted by magnetization, it means that the magnetism is insufficient and needs to be magnetized.
Why do generators still need generator chargers to charge?
Before the generator is started, it must first turn up and have a magnetic field in space to generate electricity. When the residual magnetism of the excitation system is not enough, it needs to be charged by a charger. Here charging is to charge the generator battery, which supplies power to the generator excitation system to build up the remanent magnetism.
What conditions need to be met for the generator to be paralleled?
Answer: The conditions for parallel generators to meet (1) voltage are equal at the same time. (2) The voltage phase is the same. (3) The frequencies are equal. (4) The phase sequence is the same.
1. The voltage is equal means that the voltage of the generator and the system is close (generally the difference does not exceed 10% at most). If the voltage is not equal: the consequence is that after the juxtaposition, there will be a circulating current of reactive power between the generator and the system.
2. Consistent voltage phase means that the generator voltage phase angle is close to the system voltage phase angle (generally the difference is not more than 20 degrees). Of course, if the voltage phase is inconsistent, the consequence is that a large inrush current may be generated, causing the generator to burn out. , or the end is damaged by the action of huge electric power.
3. Equal frequency means that the generator frequency is close to the system frequency (generally the difference does not exceed 0.5HZ). Similarly, if the frequencies are not equal, the consequence is that a beat voltage and a beat current will be generated. The torque generated by the active component of the beat current on the generator shaft will cause the generator to produce mechanical vibration. When the frequency difference is large, even the generator cannot be synchronized after being merged.
4. The generator needs to be connected to the grid through the synchronization device, there are manual quasi-synchronization, and there are automatic quasi-synchronization. The generator voltage and frequency need to be adjusted to meet the grid connection conditions.