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When you receive your Micro-Pack III, all sensitivity levels will be factory set for you. Each microprocessor is functionally tested in the factory for proper operation. During testing, the microprocessor is sparked using a T/R-set load. During the spark testing, the spark sensitivity level is adjusted to respond to sparking. It is possible that the sparking levels encountered at your location may be slightly different. If this is true, fine tuning upon start-up may be required.
The following details the procedures for field adjusting the microprocessor's spark and arc sensitivity levels. THE ADJUSTMENTS EXPLAINED SHOULD BE PERFORMED ONLY BY QUALIFIED PERSONNEL. Please read all applicable instructions before attempting to make any adjustments.
The following are tools that will be required for making adjustments to your microprocessor controller.
1. Oscilloscope - This device will be used for looking at wave forms and voltage levels. A storage scope is preferable for analyzing the various waveforms.
2. Screw Driver - A small screw driver is required for making the adjustments.
3. Drawings - Make sure you have all of the drawings and layouts required.
You can tell if the controller is properly adjusted for spark/arc detection by connecting a storage oscilloscope across the secondary current feedback signal. The secondary current feedback should appear as a full-wave rectified waveform.
Sparks are defined as any electrical discharge in the precipitator that will extinguish themselves without removal of power to the T/R set. Sparks generally appear as high frequency current transients on the secondary current waveform. Whenever a spark occurs, the controller should sense it and reduce the output to the setback point, then continue to slow ramp back up to the original sparking level. Quenching should not occur when a spark occurs.
The spark sense level is adjusted by potentiometer R15 on the I/O board, which is next to test point TP6*. The voltage level of R15 is read at TP6*. It is proportional to the T/R set load current. As the secondary current level increases, so will the spark sensitivity level. The factory preset level, for the spark sensitivity adjustment, is approximately .7 VDC on TP6* as read by an oscilloscope when the high-voltage is off.
This preset level may not be correct for all installations. To properly adjust this level, first remove the high-voltage to the T/R. Next, connect one probe of the oscilloscope to TP6*, and connect the other probe of the oscilloscope to the secondary current feedback test point. This test point will be labeled either TP5 or MA.
WARNING: EVEN THOUGH THE T/R HAS BEEN DEENERGIZED, HIGH-VOLTAGE IS STILL PRESENT IN THE CABINET AND 120 VAC IS PRESENT ON THE I/O BOARD. EXTREME CAUTION MUST BE TAKEN.
If necessary, adjust the voltage at TP6* to .7 VDC, then reapply the high-voltage to the T/R.
WARNING: HIGH-VOLTAGE IS PRESENT IN THE CABINET AND 120 VAC IS PRESENT ON THE I/O BOARD. EXTREME CAUTION MUST BE TAKEN.
Monitor the meters and the oscilloscope to determine if the controller is properly responding to sparks. If the controller is not responding to sparks that are occurring, the circuit is not sensitive enough. With the high-voltage still on, adjust the Spark Adjust Potentiometer, R15, clock-wise to lower the voltage on test-point TP6*. Use the oscilloscope to verify that the spark sensitivity voltage level is decreasing as the potentiometer is being turned.
If the controller is responding to sparks that are not really occurring, the circuit is too sensitive. Adjust the Spark Adjust Potentiometer, R15, counter-clock-wise to increase the voltage on test-point TP6*. Use the oscilloscope to verify that the spark sensitivity voltage level is increasing as the potentiometer is being turned.
*On some I/O boards, this test-point is labeled SPK.
Arcs, on the other hand, are defined as any electrical discharge in the precipitator that will not extinguish themselves unless the primary voltage to the T/R set is momentarily removed. Arcs generally appear to start off looking like a high frequency spark, but they have an increase in the base current level for the rest of the half-cycle. Whenever an arc occurs, the controller should sense it and initiate a quench period.
The arc sense level is adjusted by potentiometer R22 on the I/O board, which is next to either test point TP7 or ARC (depending on the revision level of the board). The voltage level of R22 is read at U10 pin 6. For new style boards, a test point, labeled ARC, has been supplied which is the same point as U10 pin 6. This voltage level is proportional to the T/R set load current. As the secondary current level increases, so will the arc sensitivity level. The factory preset level, for the arc sensitivity adjustment, is approximately 2.4 VDC on U10 pin 6 as read by an oscilloscope when the high-voltage is off.
This preset level may not be correct for all installations. To properly adjust this level, first remove the high-voltage to the T/R. Next, connect one probe of the oscilloscope to U10 pin 6,
and connect the other probe of the oscilloscope to the secondary current feedback test point. This test point will be labeled either TP5 or MA.
WARNING: EVEN THOUGH THE T/R HAS BEEN DEENERGIZED, HIGH-VOLTAGE IS STILL PRESENT IN THE CABINET AND 120 VAC IS PRESENT ON THE I/O BOARD. EXTREME CAUTION MUST BE TAKEN.
If needed, adjust the voltage at U10 pin 6 to 2.4 VDC, and then reapply the high-voltage to the T/R.
WARNING: HIGH-VOLTAGE IS PRESENT IN THE CABINET AND 120 VAC IS PRESENT ON THE I/O BOARD. EXTREME CAUTION MUST BE TAKEN.
Monitor the meters and the oscilloscope to determine if the controller is properly responding to arcs. If the controller is not responding to arcs that are occurring, the circuit is not sensitive enough. With the high-voltage still on, adjust the ARC Adjust Potentiometer, R22, clock-wise (counter-clock-wise if the board uses a multi-turn potentiometer rather than a thumbwheel) to lower the voltage on U10 pin 6. Use the oscilloscope to verify that the arc sensitivity voltage level is decreasing as the potentiometer is being turned.
If the controller is responding to arcs that are not really occurring, the circuit is too sensitive. Adjust the ARC Adjust Potentiometer, R22, counter-clock-wise (clock-wise if the board uses a multi-turn potentiometer rather than a thumbwheel) to increase the voltage on U10 pin 6. Use the oscilloscope to verify that the arc sensitivity voltage level is increasing as the potentiometer is being turned.
