Nidec 800-84132 Series Instruction Manual
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1SECTION 1INTRODUCTION ANDTHEORY OF OPERATIONINTRODUCTIONThe magnetic amplifier voltage regulator is designedto operate with brushless synchronous 400 Hzgenerators. The voltage regulator controls generatorvoltage by regulating the amount of current it suppliesthe exciter field.SPECIFICATIONSInput Power: single phase, 400 Hz, 120 VacSensing: three phase, 400 Hz, 120-139, or 208-240VacOutput: continuous maximum: 55 Vdc, 4 amperesTest Circuit: 50 Vdc (optional)THEORY OF OPERATIONNote: Refer to drawingsA. SensingA sample of the generator output voltage is applied toregulator sensing terminals E1, E2 and E3. Tapsetting H2 for 120 or 208 Vac and H3 for 139 or 240Vac. This voltage is applied to sensing transformer T1and T2, which proportionally reduces the voltage.Regulators equipped for parallel operation alsoinclude transformer T4. This circuit does not affectvoltage regulator operation in single unit operation ifthe CT leads are shorted. (See B below.)The reduced AC voltage is then fed to a rectifierconsisting of diodes D1 through D6. The rectifieroutput, which is proportional to the sensing voltage, isfiltered by capacitor C1. It is then impressed across avoltage divider circuit consisting of resistors R2 andR4, voltage range set adjust potentiometer R3, andthe externally mounted voltage adjust rheostat. Aportion of this voltage is applied to the base oftransistor Q1 in the error detector circuit.B. Sensing Circuit During Parallel GeneratorOperation in Parallel Cross-Current Compensa-tion ModeParallel cross-current compensation allows two ormore parallel generators to share reactive loads andmaintain constant system output voltage. The reac-tive error signal developed in the external parallelingcircuit is added vectorially to the sensing voltage bytransformer T4. The circuit is phased such that agenerator with excessive excitation will decreaseexcitation and an under-excited generator will in-crease excitation. At balance, each generator willcarry its share of reactive load.C. Error DetectorThe error detector is a differential amplifier. ResistorsR11 and R14 in the emitter circuit of transistors Q1and Q2 are of equal value. Therefore, when the basevoltage of Q1 is equal to the base voltage at transistorQ2, Q1 and Q2 conduction will be equal. TransistorQ2 is the reference voltage side of the error detector.Its base voltage is kept constant by zener diode Z1.The base voltage of Q1 is proportional to the sensingvoltage and the setting of the voltage adjust rheostat.Q1 base voltage will therefore increase and decreasein direct proportion to any increase or decrease in thesensing voltage or change in the setting of the voltageadjust rheostat. Operation of the error detector (Q1,Q2), second stage differential amplifier (Q3, Q4), andamplifier Q5, Q6 is as follows.An increase of Q1 base voltage will decrease Q1¶scollector voltage and increase Q2¶s collector voltage.The differential collector voltage is directly connectedto the bases of Q3 and Q4. This voltage increasesQ3¶s collector current and decreases Q2¶s collectorcurrent. The increase in Q3¶s collector current is alsoan increase in base drive to the control currentamplifier transistors Q5 and Q6. The collector currentof Q5 and Q6 and the magnetic amplifier controlcurrent increases, resulting in decreased magneticamplifier output. Conversely, a decrease in sensingvoltage results in lower conduction of transistors Q1,Q3, Q5, and Q6, a decrease in control current and anincrease in magnetic amplifier output.D. Power StageThe output power stage of the voltage regulatorrectifies 400 Hz power and feeds a regulated amountof dc power to the exciter field. The power outputstage consists of an electromagnetic filter (RFI), twofull-wave rectifiers (BR1 AND BR2) and two toroidmagnetic amplifiers (MA-1 and MA-2). The magneticamplifiers contain two windings wound about aferromagnetic core. The windings are: a power or³gate´ winding and a control winding C1 and C2. Fieldexcitation is controlled by operation of the magneticamplifiers as described in the paragraphs that followThe single phase, 400 Hz, 120 Vac power applied toregulator terminals L1 and L2 magnetizes the mag-netic amplifier core. During the time the core is being |
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