Problem Outline for Automatic Voltage Regulators
    Add a header to begin generating the table of contents

    What is AVR? What does AVR do?

    AVR, which stands for Automatic Voltage Regulator, is a device used to adjust the voltage. It is typically used in excitation generators to regulate the generator’s output voltage and control the internal excitation voltage. Essentially, it is a feedback circuit. When the generator load increases, the voltage above the generator coil drops. This signal is transmitted to the AVR, which automatically increases the upper limit of the output voltage, causing the generator’s output voltage to increase. The excitation current output from the carbon brush is also regulated by the AVR before being output to the carbon brush.

    The excitation regulator continuously adjusts the excitation current with the change of the electric load to make the generator voltage stable at the set value. It does this by measuring the generator voltage and comparing it with the given value.

    The electronic voltage regulator excites the motor and obtains the voltage through the generator’s sampling winding. It changes the output voltage by adjusting the excitation current to the rotor to be larger or smaller.

    The main function of the generator voltage regulator

    The main functions of the generator voltage regulator include maintaining the generator voltage at a specific level, adjusting the differential function, and enhancing power system stability.

    Firstly, the voltage regulator ensures that the generator voltage remains stable despite changes in load current, which can otherwise cause various issues for the power system and equipment.

    Secondly, the voltage regulator facilitates the reasonable distribution of load among parallel generator sets, preventing overloading of some generators. This function is also referred to as the regulator’s adjustment function.

    Finally, the voltage regulator helps improve the stability of the power system.

    The relationship between generator excitation regulator and governor?

    The speed regulation of a generator is primarily determined by the diesel engine or other power source, while the excitation system of the generator is regulated based on the output voltage. Typically, there are two scenarios to consider.

    Firstly, for grid-connected generator sets, the speed of the engine is relatively constant, and the generator excitation regulator adjusts the excitation current based on the output voltage. If the voltage is high, the excitation current is reduced, and if the voltage is low, the excitation current is increased.

    Secondly, for a single generator or a small generator system with variable speed loads, the control of the generator set is more complex. In this case, the generator output is required to maintain a constant voltage to frequency ratio output. This requires an additional control cycle for constant voltage to frequency ratio regulation in addition to the two aforementioned control cycles for speed regulation and excitation regulation. Therefore, when the load requires a lower speed, the engine speed needs to be controlled to decrease to the required range, and vice versa.

    What should I pay attention to when connecting the generator set voltage regulator?

    Attention should be paid to the following matters when connecting the voltage regulator for the generator set:

    1. The connection line for the voltage regulator must be connected correctly. The signal and power in and out of the generator tap line are located at the head 2 and 3, respectively. The voltage is 200V and should not be connected to 400V or higher, as it may cause burnout.

    2. Before shutting down the generator set, the reasons for any issues, such as fuses, wiring, or remanent voltage, should be checked. Do not blindly adjust the voltage regulator adjustable potentiometer and magnetization 8. Also, do not adjust the voltage regulator and magnetization while the diesel engine is idle.

    3. When the two external potentiometer appearing head 1, 2 are not connected to the potentiometer, they cannot be disconnected. When connected to the potentiometer, the potentiometer cannot be open circuit, otherwise, it may cause damage.

    4. A 12V battery must be used for magnetic field sprint, and the magnetizing unit must be in a static state. Using a 24V battery may cause high point smoke damage to the regulator.

    5. When using 50HZ or 60HZ, attention should be paid to the correct wiring to avoid affecting the normal use of the regulator.

    How to deal with the voltage instability of diesel generator sets?

    Causes and Solutions for Voltage Instability in Diesel Generator Sets:

    1. Loose wiring connections: Check all connections in the diesel generator set and repair any loose wiring.

    2. Failure of voltage-current selection switch in the control panel: Replace the switch in the diesel generator set.

    3. Failure of voltage adjustment resistor in the control panel: Replace the voltage regulator resistor.

    4. Voltage meter failure resulting in unstable display: Replace the voltage meter with a new one.

    5. Malfunctioning or improperly adjusted voltage regulator: Carefully inspect the voltage regulator and replace or adjust it as needed.

    6. Excessive vibration during operation of the diesel generator set: Check for damage to the generator set’s shock pads or any imbalance in the unit.

    7. Unstable engine speed causing voltage instability: Adjust or replace diesel fuel system parts to stabilize the engine speed.

    Explanation of generator over-excitation, under-excitation, late-phase operation, and advanced-phase operation?

    Adjusting the excitation current of a generator can cause changes in E, stator current, and power factor. Here are some possible outcomes:

    1. Normal excitation: When the stator current is kept at a minimum and cosφ=1, this is known as normal excitation. In this case, the generator only emits active power.

    2. Over-excitation: Increasing the generator excitation current beyond normal excitation (E2>E1) causes over-excitation. In this case, the stator current I lags behind the terminal voltage U, and the generator sends inductive reactive power to the grid in addition to active power.

    3. Under-excitation: Reducing the generator excitation current below normal excitation (E3<E1) causes under-excitation. In this case, the stator current I leads the terminal voltage U, and the generator sends capacitive reactive power to the grid in addition to active power. It can also absorb inductive reactive power from the grid.

    4. Phase operation: During late-phase operation, the generator supplies active power and inductive reactive power to the system, with both the active power meter and reactive power meter showing positive values. During in-phase operation, the generator supplies active power and capacitive reactive power to the system, with the active power meter indicating a positive value and the reactive power meter indicating a negative value.

    Brushless generator AVR fault judgment skills?

    When a brushless generator fails to produce electricity, it can be difficult to determine if the issue is caused by an AVR fault and where to begin troubleshooting. The following are some tips for diagnosing an AVR fault in a brushless generator:

    1. Remove the shield covering the brushless generator AVR and disconnect the F1 and F2 plug-ins from the AVR.

    2. Connect two power cables, each about 1 square in size, to the positive and negative terminals of a 12V starter battery. Connect one end of each cable to the excitation coils F1 and F2, respectively. Note that the positive terminal of the battery should be connected to F1 and the negative terminal to F2.

    3. Turn on the starter power switch and start the diesel generator, running it at 1500 rpm while observing the voltage and frequency output.

    4. When using this method, it is important to prioritize electrical safety and avoid misconnections, short circuits, and accidents.

    5. If the diesel generator speed increases and the voltage rises, with the generator voltage reaching 400V at 50HZ, it is likely that the brushless generator AVR is damaged and needs to be replaced. Conversely, if the diesel generator speed changes but the voltage and frequency remain the same, the generator is likely not producing electricity due to a cause other than an AVR fault, and other paths of troubleshooting and repair should be pursued.

    What are the reasons for the unbalanced three-phase current of the stator during the operation of the generator? How to deal with it?

    The primary causes are:

    1. Internal faults within the generator, such as stator winding inter-turn short circuit or winding disconnection.
    2. Three-phase unbalance in the system load, such as when the system has asymmetric loads like single-phase electric furnace and electric locomotive.
    3. Asymmetric faults in the system occur and the protection mechanism fails to act.
    4. The main circuit breaker of the generator is not functioning in all phases.

    Methods of treatment:

    1. Determine if the dispatch is caused by the system. If so, adjust the active and reactive loads of the generator to control the difference between the three-phase current imbalance within 8%Ie, and ensure that the maximum phase does not exceed the rated value.
    2. Address the non-full-phase fault of the main circuit breaker of the generator.
    3. If the dispatch is not caused by system failure or the main circuit breaker, conduct a comprehensive inspection of the generator, transformer outlet, etc. and carry out a power failure inspection if necessary.
    4. During three-phase current unbalanced operation, closely monitor the rotor temperature of the generator and ensure that the temperature does not exceed the allowable value.

    The role of ship generator AVR

    The marine generator AVR has the following functions:

    (1) To ensure that the terminal voltage of the generator remains constant during normal operation of the ship’s power system.

    (2) To maintain the stability of parallel operation between multiple generating sets and distribute reactive power effectively among them.

    (3) To enhance the stability of parallel operation and improve the reliability of other relay protection measures in case of a short-circuit fault in the ship’s power system by enabling the excitation system to be excited forcibly.

    What is the role of generator excitation voltage regulator (AVR)?

    The excitation voltage regulating panel is an essential component of the excitation system. Its primary function is to limit, control, and protect all necessary functions of a generator operating within its capacity. Typically, it includes a differential adjustment that samples the machine terminal voltage to adjust the excitation current and stabilize the machine terminal voltage. The principle is to regulate the output voltage, reactive power, or power factor of the synchronous generator by controlling the DC excitation level of the exciter magnetic field output to the generator. The generator set comprises the generator, steam turbine, and excitation system.

    Some generator voltage regulators require charging and magnetization. What is the reason?

    A: Firstly, check the output voltage when it is not magnetized. If it is greater than 5VAC, it is because the AVR requires a relatively high magnetizing voltage. If it is less than 4.5VAC, it is because the remanence is too low and requires magnetization.

    Is the GAVR-8A generator voltage regulator plate current limiting type or loss type?

    All of our generator automatic voltage regulators (AVRs) are of the current-limiting type, with the majority utilizing thyristor phase modulation mode and a few utilizing pulse width modulation (PWM) mode. The GAVR-8A generator voltage regulator board boasts several features, including voltage regulation accuracy of less than ±1%, compatibility with 220/380VAC brushless generators, a large 5A DC output current, the ability to select between 50/60 Hz by connecting copper sheets, a compact and lightweight design with strong weather resistance, low frequency protection and slow voltage build-up function, EMI suppression circuit, and high breaking capacity fuse protection.

    Problems with the contacts or contacts of the generator voltage regulator

    During normal operation, the current passing through the generator voltage regulator contact or contact should not cause any damage due to heat. However, when the contact is cut off, extra attention should be paid to prevent the contact surface from burning due to sparking. In some cases, the generator automatic voltage regulator may even partially melt the contact curve. The size of the spark when cutting off the current is not only related to the supply voltage, but also to the type of load.

    Inductive loads produce inductive potential when the power is cut off, which can often exceed the supply voltage. Therefore, the relay manual specifies different current values for different types of loads.

    Note that connecting multiple contacts in series or parallel does not necessarily increase the cut-off capacity exponentially. Each contact on the same relay cannot be connected and disconnected simultaneously. When connected in parallel or in series with the first disconnected contact, there is a risk of destruction.

    To increase the cut-off capacity, intermediate relays or larger relays can be used, or a spark elimination circuit can be used to eliminate smaller sparks (commonly used in automatic voltage regulator relays). Alternatively, interrupter Qin, interrupter grid, and other devices can be used to eliminate larger arcs (commonly used on the SE350 contactor).

    In AC circuits, the arc is easily extinguished at the moment of crossing zero, so the value of the current allowed to be cut off is larger than that of DC circuits.

    How to deal with the black smoke from Cummins generator voltage regulator plate?

    Firstly, it is important to check for any potential blockages in the air filter, exhaust back pressure, oil nozzle, and the tightening force of the Cummins actuator cylinder. These factors could be the root cause of the issue.

    There are several potential causes of the problem, including a severely blocked air filter, poor fuel quality, excessive exhaust back pressure, fuel injection pump failure, faulty oil nozzle atomization, and insufficient tightening force of the Cummins actuator cylinder.

    To address the issue, the following steps should be taken:

    1. Check the air filter for any blockages
    2. Verify the quality of the fuel being used
    3. Adjust the fuel supply by the pump as needed
    4. Inspect the oil nozzle for proper atomization
    5. Ensure that the cylinder tightening force is within normal range.

    How to adjust the generator to replace the automatic voltage regulator (AVR) before it can be connected to the grid?

    When replacing the automatic voltage regulator (AVR) of a generator, it is not possible to manually connect to the grid. The synchronization of frequency, voltage, and phase sequence is a prerequisite for grid connection. This requires the installation of a special diesel generator grid connection controller to monitor the state of the grid and the diesel generator in real-time and adjust the voltage and frequency of the diesel generator to match the grid. Additionally, for safety reasons, intelligent circuit breakers should be installed to trip and provide protection in the event of an abnormal situation.

    Before connecting to the grid, it is necessary to synchronize the phase sequence and adjust the voltage and frequency to ensure consistency between the two units. The power distribution and reverse power should also be adjusted as needed. If there is an out-of-step situation or reverse power, adjustments must be made accordingly. Finally, the parallel load switch should be adjusted to ensure that the parallel loop current is zero. Once these requirements are met, grid paralleling can be achieved.

    How to judge the quality of the voltage regulating plate (AVR)?

    To determine the functionality of the regulator board (AVR) after confirming the normalcy of the winding coils, locate the F1.F2 excitation power line and use a battery as the power source for magnetization. Connect the positive pole to F1 and the negative pole to F2 (to be connected). When the starter unit reaches the rated speed, connect F2 to the negative pole of the battery. The following conditions may occur:

    1. If a voltage of ≥ 400V (determined by the battery voltage) is established, use a multimeter to check for AC190-220V on P2.P3.P4AVR detection voltage. If present, the detection line is normal. Next, check for DC40-90V voltage output on F1 and F2 of the AVR. If present, the regulator (AVR) is intact. If there is no DC voltage output or the output is very low, it proves that the AVR is faulty.

    2. If no voltage is established or the DC voltage is ≤ 30V, it is likely that the winding is normal and the exciter rectifier secondary tube or surge elimination tube is damaged. In this case, the AVR fault should be excluded and focus should be placed on checking the rectifier diode.

    Shopping Cart
    Scroll to Top