CHAPTER 3: INSTALLATION WIRINGC70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL 3-1533.3.6 Contact inputs and outputsEvery contact input/output module has 24 terminal connections. They are arranged as three terminals per row, with eightrows in total. A given row of three terminals can be used for the outputs of one relay. For example, for form-C relay outputs,the terminals connect to the normally open (NO), normally closed (NC), and common contacts of the relay. For a form-Aoutput, there are options of using current or voltage detection for feature supervision, depending on the module ordered.The terminal configuration for contact inputs is different for the two applications.The contact inputs are grouped with a common return. The input/output modules have two versions of grouping: fourinputs per common return and two inputs per common return. When a contact input/output module is ordered, four inputsper common is used. If the inputs must be isolated per row, then two inputs per common return are selected (4D module).The tables and diagrams on the following pages illustrate the module types (6A and so on) and contact arrangements thatcan be ordered for the relay. Since an entire row is used for a single contact output, the name is assigned using the moduleslot position and row number. However, since there are two contact inputs per row, these names are assigned by moduleslot position, row number, and column position.Some form-A / solid-state relay outputs include circuits to monitor the DC voltage across the output contact when it isopen, and the DC current through the output contact when it is closed. Each of the monitors contains a level detectorwhose output is set to logic “On = 1” when the current in the circuit is above the threshold setting. The voltage monitor isset to “On = 1” when there is a voltage across open contact (the detector allows a current of about 1 to 2.5 mA), and thecurrent monitor is set to “On = 1” when the current flowing through the closed contact exceeds about 80 to 100 mA. Thevoltage monitor is intended to check the health of the overall trip circuit, and the current monitor can be used to seal-inthe output contact until an external contact has interrupted current flow. If enabled, the current monitoring can be used asa seal-in signal to ensure that the form-A contact does not attempt to break the energized inductive coil circuit and weldthe output contacts.Block diagrams are shown as follows for form-A and solid-state relay outputs with optional voltage monitor, optionalcurrent monitor, and with no monitoring. The actual values shown for contact output 1 are the same for all contactoutputs. Form-A contact output with or without a current or voltage monitoring option is not polarity sensitive. The polarityshown in the figure is required for solid-state contact output connection.Figure 3-13: Form-A and solid-state contact outputs with voltage and current monitoring
