Each device in the unit is mounted on an appropriate heat sink and is protected

Each device in the unit is mounted on an appropriate

This preview shows page 50 - 52 out of 69 pages.

converter, and also single phase AC voltage controller power circuits. Each device in the unit is mounted on an appropriate heat sink and is protected by snubber circuit. Short circuit protection is achieved using glass fuses. A circuit breaker is provided in series with the input supply for over load protection and to switch ON/OFF the supply to the power circuit. The Gate and Cathode of each SCR’s brought out on the front panel for firing pulse connection. A digital voltmeter and an ammeter is mounted on the front panel to measure the armature voltage and current. All devices schematic is printed on the front panel. Specifications: Input : 10V to 230V single phase SCR : (V) rrm 1200V, (I) av : 10 amps, 25TTS12 International rectifier make. Power diodes & Free Wheeling diode : (V) rrm : 1200V, (I) 16 amps, 12KLR 16DS Fuses : 6 Amps Glass fuses MCB : Two pole 6 amps / 230V Heat Sink : PI-46, 50mm Snubber : R-250 Ohms / 5 Watts c-0.1 Microfarad / 1000V Front Panel Details: AC Input : Terminals to connect 1-phase AC input from single phase isolation transformer. Output : Terminals after the MCB to be connected to power circuit Digital voltmeter : 3 ½ digit voltmeter to measure output voltage Digital ammeter : 3 ½ digital ammeter to measure output voltage Circuit Breaker : 6 Amps, AC power ON/OFF to the circuit and for protection T 1 , T 2 : Trigger pulse connections from the firing circuit D 2 , D 4 : Power diodes
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51 D m : Free wheeling diode Field (+and-) : Field supply for DC motor for motor control experiments. (With indicator) Back Panel Details: 3 pin mains socket for AC mains supply to field supply bridge rectifier Glass fuse holders for 6 fuses in series with each SCR’s. Procedure: Switch ON the mains supply to the single phase converter firing circuit. Observe the test points and trigger outputs. Verify the trigger outputs and their phase sequence. Vary the firing angle potentiometer and observe the trigger outputs. The pulse train width will increase as we decrease the firing angle from 180 o to 0 o . It is 0 o to 180 o and 50% at 90 o soft start and stop feature is provided for trigger outputs. When we press of ON/OFF switch the trigger outputs will start at 180 o and slowly increased to the firing angle set by firing angle potentiometer. The acceleration time is set in the factor (10 seconds). When we release the ON/OFF switch the trigger outputs will slowly decreased to 180 o from the set firing angle. The deceleration time is set in the factory.(-2 seconds) The deceleration time is very short compared to acceleration time. Make sure that all the trigger outputs are proper before connecting to the power circuits. Make the connections in the power circuit as given in the circuit through isolation transformer. Initially keep the input supply at low voltage say 30 volts. Connect the trigger outputs from firing circuit to the corresponding SCR’s Gate and Cathode. Initially connect a Rheostat of 50 Ohms / 5amps. Switch ON the trigger outputs observe the voltage waveforms across load by varying the firing angle potentiometer. Compare with the expected waveforms, if the unit is working properly switch OFF the trigger outputs and switch OFF the MCB. Connect field terminals of DC motor to the field supply points in the power circuit.
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  • Winter '20
  • Combustion, Rectifier, single phase, SCRs

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