INSTRUCTION MANUAL Basler Electric Highland, Illinois Voltage Regulator Model: kT-38 Part Number: 90 24700 101 Publication Number: 90 24700 991 Date: March 14, 1977 Change 1: November, 1980SECTION 1.0 GENERAL INFORMATION 1a The voltage regulator herein discussed; maintains the output voltage of an ac generator at a constant value by controlling the current through its field. When a brush type exciter is used with the generator, the regulator then controls the current through the exciter field. 112 The regulator is a static control device using a multi-tap sensing transformer silicon semiconductors, capacitors and resistors. All ‘the components are contained in a protective enclosure. The unit is not subject to wear from any moving parts and it is relatively unaffected by temperature, vibration and shock. 1.2 PURPOSE 1.2.1 The voltage regulator is designed for use in an excitation systen for ac generators rated up to 75 KW with a rated armature and field winding of 125 volts. The regulator uses the de armature voltage of the exciter as the source of the regulator power and it is capable of acting as a stepless, infinitely-variable field rheostat. 1.2.2 Cranking exciter applications. 1.2.2.1 The KT-38 voltage regulator can be used for applications using the rotary exciter as a cranking motor during start cycles. 1.2.3 Single phase generators. 1.2.3.1 The voltage regulator can operate properly with single phase generators larger than approximately 1 KVA, and can be operated on reconnectable single or three phase generators and on both two and three wire single phase generators. 1.2.4 Parallel provisions. 1.2.4.1 Standard 25 VA, 5 amperes secondary current transforners (CT's) may be used in conjunction with a Basler APM-300 paralleling module, (three Phase generators) or the APM 301 for single phase generators.1.3 SPECIFICATIONS Input Sensing: (Terminals E1 and £3) Voltage (Vac) Frequency (Hz) Phase Input Power: Output Power: Nominal Voltage Forcing Voltage Current. Current Limiting - Minimum (Cold) Field Resistance Voltage Adjust Range Voltage Regulation - Short Circuit Performance - Reverse Voltage - Anbient Operating Temperature Mounting - Weight Bert 120/208 /240/416/480 50-60 1 The regulator is designed for use in an excitation system for_ac generators rated up to 75 KW with a rated armature and field winding of 125 volts. 125 Vde 180 Vde +04 to 2 amperes The current is limited by armature saturation voltage and series resistance in field current. 34 Ohms, + 10% of nominal Less than + 1% for 100% alternator loading and for + 10% frequency changes. Up to 6 amperes continuous duty capability to the exciter field during short circuits and overloads. The regulator is not damaged when connected to an exciter with reversed residual voltage. -30°C to +60°C (-22°F to +140°F) Unit is designed to operate satisfactorily when mounted on gasoline, diesel or turbine generator installations. 4,5 1b. (2.04 Kg) NetSECTION 2.0 2a PRINCIPLES OF OPERATION 21d The regulator acts as an automatic field rheostat which precisely controls the field current in order to maintain a constant output voltage of the ac generator. Initially current flowing through resistors R12 and R10 causes current to flow in transistors Q2, Q3, Q4, Q5, and 06 (see Figure 1). The ac generator voltage at terminals El and £3 in the sensing circuit is stepped down, rectified and filtered to form a dc sensing signal. A fraction of this signal is compared to the voltage across reference diode VR1 to develop an error signal. When the ac generator voltage becomes too high, the sensing circuit produces a positive error signal which is applied to the base of the transistor Ql. This causes an increase in the collector current of Ql and a corresponding decrease in the current through 02, 03, 04, Q5, and 6. To minimize power loss, the power transistors operate in a switching manner in variable turn-on duty cycles. 2.1.2 When the regulator is used in a system that includes a conventional rotary inverter the power for the field and regulator is taken from the armature of the exciter (see Figure 3). 2.2 INSTALLATION 2.2.1 A free convection flow of cooling air must be allowed to circulate through the unit. The unit should not be mounted near other heat generating equipment or mounted inside totally enclosed switchgears without, ducts to outside cooling air. The regulator can be mounted in any position without affecting its regulating characteristics. The dimensions of the regulator are shown in Figure 2. To obtain maximum cooling, insure the open ends of the regulator are vertical when mounted. 2.2.2 The voltage regulator must be connected to the generator system exactly as indicated in the interconnection diagram (Figure 3). A thorough check and test should be made to determine that all connections are made to all terminals in the manner specified. An electrical test using an ohmmeter is the preferred method of checking for correct connections. Number 18 gauge wire or larger should be used to connect the voltage regulator in order to carry the required currents. Basler Eloctrc ohind osSECTION 3.0 OPERATION 3.1 GENERAL INFORMATION 3.11 The voltage regulator should be operated only at voltages and Frequencies specified for the equipment. The speed of the prime mover should be the normal operating speed corresponding to the normal output frequency of the generator. If operation at reduced speed is required, then place switch SKI in the OFF position in order to prevent possible damage to the regulator and the load equipment. (See Figure 3.) 3.2 FIELD FLASHING 3.2.1 Normally there is a sufficient amount of residual output voltage (3-5 Vdc) for the exciter to initiate a build-up of generator voltage. For new installations or for operation after prolonged shutdowns, it may be necessary to flash the field to obtain build-up. Figure 3 shows the preferred field flashing set up, incorporating a pushbutton switch in addition to the SPDT switch (SW 1), which allows momentary applications of the field flashing voltage when SW1 15 in the OFF position. Switch SW1 should be placed in the ON position immediately after the generator output voltage begins to build up. 3.2.2 Voltage in excess of 120 volts direct current must not be used as a field flashing source. Contact the factory for further information. 3.4 ADJUSTMENT CAUTION DURING THE VOLTAGE ADJUSTMENT, INSURE THAT THE METAL SHANK OF THE SCREWDRIVER DOES NOT TOUCH THE SIDES OF THE OPENING OR ANY OTHER METALLIC OBJECT. 3.4.1 An internal variable resistor (R6) is provided for adjusting the regulated voltage over a range of + 10% of the nominal voltage. The adjustment can be made with a screwdriver inserted through the opening in one side of the unit. A variable resistor can be series connected in either sensing line (terminals £1 and £3) to provide an external voltage adjustment (see Figure 3). 3.5 PARALLEL OPERATION The APM 300 and APH 301 Paralleling Modules are available to provide parallel operation of two or more regulators. 4 aSECTION 4.0 4.1 PREVENTIVE MAINTENANCE 4.1.1 The voltage regulator should give years of trouble-free service with reasonable care. The following preventive maintenance should be performed: a. Dust the unit periodically and keep air screens, vents or ducts free of accumulated dust and other foreign material. Use a soft bristle brush or an air line with a filter and a moisture trap. b. Insure that the air supply 1s not blocked. The unit will overheat if the air flow 1s cut off. 4.2 CORRECTIVE MAINTENANCE 4.2.1 Simple repairs to the unit can be made following the schematic diagram (Figure 1). Because of the complexity of the printed circuit board in the regulator, complicated repairs should be performed only by the manufacturer. It is recomended that a spare unit be stocked to avoid shut-down time in the event the original unit requires repair. Basler Electric Company maintains a supply of the units and components parts in stock at all times. 4.3 TROUBLESHOOTING 4.3.1 Some of the possible malfunctions that could occur during the installations of the voltage regulator and the appropriate corrective procedures are listed on the next page. Bauraz44 TROUBLESHOOTING CHART YPTOR “PROBABLE CAUSE SOLUTION No voltage Residual magnetism too weak or | Flash the field with build-up improper polarity. correct polarity following the pro- cedure of paragraph 4.3, Generator output voltage rises to maximum voltage. Open leads between input terminals £1 and £3 of regulator and generator terminals. Terminals E1 connected to wrong terminals on transformer Tl. Correct open circuit. Make correct connection. Generator voltage constant but below normal. Terminal £1 connected to wrong terminals on transformer Tl. Make correct connection. Generator output erratic. Badly worn dirty or improperly seated brushes. Dirty commutator. Replace, clean or reseat brushes. Clean conmutator. REPLACEMENT PARTS LIST Reference Transformer 1 Printed Circuit Board Assembly -- Transistor 3, 95 Transistor 4, Q6 Diode R3, CRB, CRI Voltage Adjust Rheostat R6 Basler Part Number BE 01315 001 90 24703 101 05249 05250 06721 03483WV¥OVIG DILWW3HDS - | 3INDId zaoVOLTAGE ADJUST 2,594" b6.388) i = os}. ¢f feu ag ES : 4 ee Dimensions are in inches cw and centimeters ( ). FIGURE 2 - OUTLINE DRAWINGWV¥OVId NOILDINNOODYILNI ~ € 3’NDId YOLVINDIY IOVLIOA gen [>> 4 ©) NoLINeHsnd Hsvid aiald *suo}}oeuu0s joucyido AUBLLVE 1 4109419 paysoq ¢ = ONIHsv14 o73id_uaLtoK3 x0 T — anald yo Og - AOBy aq o-== wy 90S - AILY *pepuouuooo. s stom 67 wyo St - Adve #0 Buygos wong wyo YSt - AgOZ wyo 5 - AOZL (12veudo) Isnlpy BEDsIOq uD YE “Yyouims umopinys-a4o1edo ms \7 7313 NoivuaNao 0 avoi ¢ wo vOBasler Electric 12570 State Route 143 Highland IL 62249-1074 USA www.basler.com, info@bastler.com Phone +1 618.654.2341 Fax +1 618.654.2351