ELBOW 2P7737 - Caterpillar

Illustration 1 g00481725
Functional Block Diagram Of AC Voltage Display in EMCP II
Table 1
AC Voltage Range Selection    
GSC P20 Setpoint    External Potential Transformer    AC Transformer Box (ATB) Input Voltage Range    GSC Internal Multiplier    Jumper    
700     None     0 - 700     5     Required    
150     None     0 - 150     1     None    
300     2:1     0 - 150     2     None    
500     3.33:1     0 - 150     3.33     None    
600     4:1     0 - 150     4     None    
750     5:1     0 - 150     5     None    
3000     20:1     0 - 150     20     None    
4500     30:1     0 - 150     30     None    
5250     35:1     0 - 150     35     None    
9000     60:1     0 - 150     60     None    
15000     100:1     0 - 150     100     None    
18000     120:1     0 - 150     120     None    
30000     200:1     0 - 150     200     None    The AC voltage and/or current values are inaccurate.Note: For related information, see Testing And Adjusting, "AC Voltage Range - Adjust"The P20 setpoint determines the proper AC voltage range and the internal multiplier that are used by the GSC for calculating AC voltage. The GSC uses the internal multiplier to compensate for the turns ratio of the external potential transformers (if present). The turns ratio of the external potential transformer must match the internal multiplier in order to ensure an accurate AC voltage calculation by the GSC.The jumper block is located in the relay module. The jumper block connects a "divide-by-five circuit" to the AC voltage input of the GSC. The "divide-by-five circuit" reduces the AC voltage input to a controllable level for the GSC when P20 is 700. When setpoint P20 is 700, a multiplier of five is needed to compensate for the presence of the "divide-by-five circuit". This is done even though no external potential transformer is present.Note: In order to prevent an inaccurate voltage calculation by the GSC, the jumper block should NOT be installed when P20 is programmed to a value that is different from 700. The other values (150 through 30 000) are used with an external potential transformer. The values result in input voltages from 0 to 150 ACV at the AC Transformer Box (ATB). No further reduction of the input voltage is required.Do the following procedure to determine the cause of inaccurate AC voltage and/or current values on the GSC.
Check setpoints P20 (full scale voltage) and P21 (full scale current). In order for the GSC to operate correctly, the current transformers (CT) must have 5 amp secondaries. See Testing And Adjusting, "Engine/Generator Setpoint Viewing OP2" and Testing And Adjusting, "Engine/Generator Programming OP5". Typical factory setpoints are as follows: 700 V for P20 and 600 A for P21. The