Motor Control, Solid-State

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Contactors

Current Monitoring Operation

Product Description

The Bulletin 156-B… P or …N Current-Monitoring Solid-State Contactor (SSC) is a single-phase device that is sensitive to variations in load current conditions. This microprocessor-based device can detect a partial load failure and ensure the highest process quality. Current sensing is integrated inside to eliminate the need to install an external current transformer. A membrane TEACH button on the front is used to effect a simple “teach in” of the normal operating current setpoint. Alarm delay time is set by a potentiometer. Typical conditions that can be detected are heater break or open-circuit, blown fuse, semiconductor short-circuit and faulty power connection.
A 13% reduction from normal operation (TEACH current level) triggers a current alarm. SSC over-temperature protection is integrated as a standard feature.
The product is ready to mount on DIN Rail or chassis and comes with integral heatsink. The standard 45 mm housing dimensions enable straightforward replacement of alternative products.

Alarm Operation

Current Setpoint
The current setpoint is the nominal operating current that is expected when all the heater loads are functioning properly. If the heater loads are faulty or the supply voltage is not close to the nominal level, the wrong setpoint will be stored during TEACH.

Initialization
As shipped, no setpoint is stored in the SSC flash memory. Both green and red LEDs will flash intermittently to indicate that a setpoint must be stored using the TEACH procedure. The load will not go on when the control is applied until a TEACH command is successful.

Local Functions
Local functions can be activated by using the TEACH push button on the front of the SSC. While an alarm is being issued by any SSC connected to the common alarm line or a remote command is being issued, no local commands are accepted.

Local TEACH
Press and hold the TEACH button for approximately 3 seconds. The red LED will flash after each second. After the LED flashes 3 times, release the button. If the “teach” command was accepted, the heater loads are automatically switched ON. The red LED will flash quickly 10 times. When the current setpoint has been stored successfully, the red and green LEDs will scroll intermittently to indicate that the TEACH procedure has been completed. The load will now be switched on or off according to the control input’s status.

It is very important to hold the button down for only 3 flashes of the red LED to make a successful TEACH. If the TEACH procedure is not successful, the SSC will automatically reset to factory default (i.e., no setpoint stored).

Local RESET
When an alarm has occurred the device can be locally RESET by pressing the TEACH button for 1 second. The red LED will flash once. This will reset the alarm. If the alarm condition has been cleared the SSC will return to normal operation. If the alarm condition is still active, the SSC will automatically go back to alarm status.

Local TEST
In the absence of a signal on the “control input” terminal, a local TEST can be made by pressing and holding the TEACH button for 5 seconds. After the red LED flashes 5 times, release the button. The SSC will switch ON the load for 1 second. This test detects if there is an undercurrent or heater break alarm condition.

Remote Setup Procedure
Remote functions can be activated with a PLC or any other logic controller by applying timed pulses to the alarm terminal: >10V for Cat. No. 156-B…P and <10V for 156-B…N.

Remote TEACH
Apply a 3-second pulse. The red LED will flash after each second. After the LED flashes 3 times and the remote “teach” command has been accepted, the heater loads (of all SSCs connected to the same alarm line) are automatically switched ON and the red LED will flash quickly 10 times. When the current setpoint has been stored successfully, the red and green LEDs will scroll intermittently to indicate that the TEACH procedure has been completed. The load(s) will now be switched on or off according to the control input’s status

Remote RESET/ UNBLOCK
When an alarm has occurred the SSC can be remotely RESET by applying a 1-second pulse. A 1-second pulse will also unblock local TEACH of all SSCs connected to the same alarm line. The red LED will flash once. This will reset the alarm. If the alarm condition has been cleared the SSC will return to normal operation. If the alarm condition is still active, the SSC will automatically go back to alarm status.

Remote BLOCK
Applying a 5-second pulse will force the SSC to block local TEACH. After this, no local TEACH commands are accepted. To unblock this condition, a remote RESET must be issued. If the 24V supply is removed, local TEACH BLOCK is lost. Another REMOTE BLOCK must be issued.

Alarms

Alarm DELAY
A potentiometer on the front of the SSC allows a time delay on the heater break alarm between 0…40 s.

For heaters having a low cold resistance, the time for the inrush current to decay to a value less than 13% of the current set-point plus an additional 20 ms must be added to the potentiometer alarm delay setting.

For an alarm signal to occur, the alarm condition must persist throughout this time period. The alarm output is enabled only after this time delay has passed. However, if the control input is disabled for a period of time equal to four times the delay setting, the internal alarm delay timer is reset automatically. (See Alarm Operation graphs.)

SSC remains OFF due to Line Voltage Loss or Thyristor Open Circuit Failure (Reaction Time = 85 ms)
The SSC generates one pulse with duration of 7 seconds on the alarm terminal. This alarm is non-latching. The red LED remains ON after this alarm condition until a RESET is issued.

Heater Break
A Heater Break alarm is given if the current measured through the SSC is 13% less than the current setpoint stored in the flash memory for a period of time greater or equal to the alarm delay potentiometer setting. The SSC generates one pulse with duration of 8 seconds on the alarm terminal. The alarm signal is non-latching. The red LED remains ON after this alarm condition until a RESET is made. If the measured current changes to within 10% of the Current Setpoint, before the Alarm DELAY time has elapsed, the Alarm DELAY timer is reset.

Overtemperature or Overcurrent
This alarm occurs if any one of following two conditions is true:
1. The SSC detects an internal over-temperature condition at any time during operation and switches off the output. The red LED flashes intermittently.
2. A current above the nominal SSC rating is measured during current setpoint TEACH. This action erases the current setpoint from flash memory and both red and green LEDs will flash intermittently until a TEACH procedure with an acceptable current is carried out.
In both cases, the SSC generates one pulse with duration of 9 seconds on the alarm terminal. The alarm signal is non-latching.

Thyristor Short-Circuit (Reaction time = 110 ms)
The SSC generates one pulse with duration of 10 seconds on the alarm terminal. The alarm signal is non-latching.
The red LED remains ON after this alarm condition until a RESET is made.

Alarms Connected in Parallel to one PLC Input and one PLC Output
For REMOTE operation, up to 50 SSCs can be connected in parallel to at least one PLC input. This PLC input must also be connected in parallel to the PLC output. The PLC input must be programmed to detect alarms while the PLC output must be programmed to supply the pulses required for REMOTE Setup. When more than one SSC is present, pulses from the PLC output or alarm pulses from any device will cause the red LEDs on all devices in parallel to flash intermittently for a max. of 6.25 seconds. After this time, it is only SSCs with an alarm condition that will have their red LED on.

Example:

Set the alarm delay setting to 2 s (minimum). If the full load current is set at 30 A, then there will be an alarm condition if the current is under 26.1 A for more than 2 s. (Any fluctutation in the load current that is present for <2 s will not be signalled – this is intended to eliminate false alarms due to short duration undervoltage conditions on the supply phase). If the control input goes off within the 2 s, the alarm timer will not be reset provided the control input goes on again within 8 s (4x2 s).

Alarm Operation





Setup and Alarms