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In single operation, the alternator voltage is held constant irrespective of power, frequency and temperature. When operated in parallel with the mains or with other alternators, a stable reactive power is produced. Stable reactive power thanks to current-voltage vector measuring system droop.
A load-relieved current transformer is required in alternator phase V. Internal and external alternator voltage set-point adjustment. PID control amplifier with large adjustment range.
Disproportionate drop in desired value when alternator operates at underfrequency. Permanent monitoring of the actuator and time limit on the max. Internal protection devices trip whenever a fault occurs, thus separating the excitation field from its energy source.
Compact construction with interchangeable power stage. Fully potted in to protect it from environmental effects. Long life thanks to high-quality components. Brief summary 2. To allow the trend of the control property following a change in the P or I parameter to be evaluated, the load connected must be reproducible. The factor with the greatest general significance in achieving an optimum regulating system is an overshoot amplitude xm which is as small as possible.
The essential criterion in the evaluation of the regulating process with respect to time is the settling time taus. It is not necessary to adjust the D parameter in order to optimise the control properties. It is generally determined just once, in accordance with the size of the alternator. To decide whether the D parameter should be increased beyond this, it is necessary to take specific measurements of the alternator voltage and at the output of the regulator. Satisfactory optimisation of the regulator will normally be achieved by the free adjustment of the P and I parameters.
To follow the trend of the control property, use an oscilloscope to monitor the manipulated variable. The D parameter can be switched over in two stages using code switch S2.
Figure 4 Characteristic quantities of the regulating system Figure 5 Trend of the control property 6. Functional description 3. The nominal power should be at least VA. Caution: If the auxiliary excitation voltage is taken from a constant "external" power source e. When switching off the alternator, the supply should be switched off before the machine comes to a halt see External power supply. To measure higher voltages, corresponding voltage transformers must be connected in series.
Signal input N allows intervention into the internal formation of the actual value. The secondary AC measurement voltage of the measuring transformer is converted into a DC voltage, smoothed, conditioned and output as an actual value to the regulator circuit. The measured value which is produced corresponds to the arithmetic mean of the rectified three-phase AC measurement voltage. Three-phase measurement allows for asymmetric loads. Note: For non-linear loads static thyristor converter or rectifier , additional module TF RC low-pass filter is recommended as a measuring adapter.
High non-linear loads may require overdimensioning of the alternator. The signal input n allows intervention in the internal formation of the desired value. In parallel operation of the alternator, the reference voltage is influenced by the droop-measuring system see 3. The ES additional module allows the adjustment range of the external set-point potentiometer to be extended from remanence to the nominal voltage.
This must be decided on a case by case basis, depending on the application and the excitation system used auxiliary excitation windings or auxiliary excitation machine? To stabilise the alternator reactive current it is therefore necessary to have a measured variable which is dependent on the reactive current and incorporates the magnitude of the current and the reactive power inductive or capacitive.
This measured variable is introduced at the addition point comparison point of the desired value and the actual value of the control amplifier circuit. This produces a static droop control characteristic, which represents the relationship between: the change in the alternator voltage in relation to the nominal voltage and the change in the alternator reactive current in relation to the nominal current. The droop is represented by the slope of the characteristic curve produced i. In parallel operation, regulation of the synchronous alternator is made possible by the droop sensing signal.
For stand-alone operation, adjustment is performed on the test rig using a reactive load. In AvK synchronous machines, the corresponding current transformer is located in phase V.
The K side of the transformers points towards the alternator s main winding see Figure 6 Block diagram. Internally load-relieved bushing-type transformers are used. The wire marked in white is the secondary-side k point. In the case of alternators for parallel and stand-alone operation, the measuring input k I can be short-circuited by means of a switch for stand-alone operation. This gives better voltage stability see 8.
Diagrams of connections, If the direction of rotation is reversed, measuring leads U and W should be interchanged.
The parameter of the I section can be varied in steps from 1 to F using switch S 1. During this process, the integration time constant increases. The parameter of the P section can be varied by means of potentiometer R 1. During this process, the adjustment range shown in Figure 8 should not be exceeded. Above the kink point, voltage regulation is constant. The voltage reduction is delayed by about 2 seconds to eliminate the effect of transient drops in the speed of the drive machine.
In exceptional circumstances, the underspeed protection function can be deactivated by means of code switch S2.
Code switch S2. For other nominal frequencies, the UF module should be used or the alternator should be deexcited when being shut down. Figure 8 P adjustment range Further adjustment in the clockwise direction leads to hunting, while further adjustment in the anticlockwise direction leads to control errors.
The D parameter can be changed by switching code switch S2. The D parameter can furthermore be varied at the D-Opt. At the specified polarity, a capacitor can additionally be soldered in. Figure 9 Underspeed protection Protective functions The auxiliary exciter windings see 3. If the actuator is faulty, the high short-circuit power involved may cause severe damage. The reduction for underspeed is indicated by H1. If this state is allowed to continue, the exciter system will be damaged. However, the fully-on state only occurs in the case of compensating processes or short circuits at the main terminals of the alternator.
After this, the protection circuit isolates the exciter field from the source of excitation energy by tripping the protection fuses. Checking the direction of action of the control amplifier and the actuator This feature monitors the positioning transistor for short circuits. Short-circuiting of the positioning transistor leads to maximum excitation.
The control amplifier tries to counteract this but has no effect on the faulty actuator. The actuator and the control amplifier act in opposite directions and the fuses trip immediately. The excitation energy is taken from the rectified supply voltage, the rectifier circuit being located in the power stage. It allows the rectification of two single-phase or three-phase supply voltages see 3.
There is a short-circuit thyristor in the DC circuit. Caution: Fuse: 10 A super quick-acting 32 mm x 6. The power stage may suffer permanent damage if the wrong type of fuse is used. The power stage is located on a profiled heat sink. To ensure adequate cooling for the power semi-conductors in the power stage, you must follow the instructions in Chapter Extreme overloading of the alternator short circuit if this has not been switched off after 8 to 10 seconds.
Note: Additional module ER1 can be used to limit the excitation current when the alternator is operated in parallel. Special functions and additional equipment 5. The alternator is regulated by one of these regulators main regulator.
If this regulator is defective, it is possible to switch to the second stand-by regulator. Stand-by circuits are available in either manual or automatic form. Manual stand-by circuit SB1 In the event of a malfunction, a changeover switch permits the stand-by regulator to be selected. The changeover switch switches over all the signals apart from the sensing voltage and supply connections UH2 VH1 and WH2.
Automatic stand-by circuit SB2 The stand-by circuit monitors the main regulator. Common operating variables with respect to the response of the regulator allow fault detection and switchover to the stand-by regulator. The stand-by regulator operates in simulated control mode and is likewise monitored. The switch between the two regulators can take place during the operation of the alternator and can be performed manually, by means of a test function or, in the case of a malfunction, automatically.
Switch contacts should be connected to the double terminals to de-excite the alternator when they open see Figure 34 De-excitation circuit. These de-excitation contacts must meet the following specification: Current carrying capacity AAC Voltage carrying capacity V AC The switch elements used must have dust-protected contact chambers. Ensure that contact resistance is low the contacts must be sensitive to low-level signals.
Note: One of the factors which determines the build-up of excitation is the quality of these contacts. Rotary coil or moving-iron instruments are recommended.
Description and adjustment instructions COSIMAT N+ voltage regulator for DSG and DIG alternators
In single operation, the alternator voltage is held constant irrespective of power, frequency and temperature. When operated in parallel with the mains or with other alternators, a stable reactive power is produced. Stable reactive power thanks to current-voltage vector measuring system droop. A load-relieved current transformer is required in alternator phase V. Internal and external alternator voltage set-point adjustment. PID control amplifier with large adjustment range. Disproportionate drop in desired value when alternator operates at underfrequency.
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