Bender RCM420 Series Bulletin technique - Page 2

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BENDER Inc. • 700 Fox Chase, Coatesville PA 19320 • Ph: 800-356-4266 / 610-383-9200 • Fax: 610-383-7100

RCM420 Series

RCM420

Features

• Ground fault monitoring for AC grounded

systems

• True RMS value measurement (AC)

• External measuring current transformer

• Two separately adjustable response values

• Frequency range 42 - 2000 Hz

• 3 seperately adjustable time delays:

startup, response, and release

• Restart function

• LCD screen with real-time value display

• Latching or non-latching operating mode

• CT connection monitoring

• Power On LED, LED Alarm 1 / 2

• TEST / RESET button, internal / external

• Two separate voltage-free SPDT contacts

• Normally energized or de-energized

operation (selectable)

• Password protection

• Device self monitoring

• Sealable transparent cover

• Small form factor

• Conforms to RoHS

Approvals

Description

The RCM420 monitors for ground faults in grounded and high-resistance grounded AC

systems, both single- and three-phase. The RCM420 is specially designed to provide ad-

vanced warning of developing ground faults without the problems associated with high

sensitivity nuisance tripping.

A digital LCD screen displays real-time measurements of the system's ground fault cur-

rent. Two separately adjustable SPDT contacts allow for information transmission (such

as to a PLC) or power interruption (such as through a contactor or shunt trip breaker).

Since the values are measured with measuring current trans formers, the device is nearly

independent of the load current and the nominal voltage of the system.

Applications

• Ground fault detection in single- or three-phase AC systems

• Motor and motor control systems

• Heat tracing systems

• Current monitoring of normally offline single conductors

• Alarm systems, safety devices

• HVAC systems

• Generators, portable and fixed

• Industrial controls

Function

Once the supply voltage U

is applied,the starting delay ("t") activates. Alarms during this

delay will not cause the RCM420 to switch over the contacts.

Measurements of the system's ground fault current are taken via an external current trans-

former. All phases (including the neutral if one exists) are placed through the current trans-

former. The measured value is indicated in real-time on the device's LCD display.

If the measured value exceeds one or both response values, the respective response delays

activate. If the ground fault still exists after the response delays expire, the respec-

on1 / 2

tive contacts switch over and the alarm LEDs activate. If the device is set to non-latching

mode and the ground fault clears, the alarms will clear after the set release time "t

pires. If the device is set to latching mode, the alarms will not clear until the device is re-

set manually or the supply voltage is lost. The TEST function allows for an internal opera-

tion testing of the device. The device's easy-to-use onboard menu manages all settings via

the detailed LCD screen. An optional password protection setting protects unauthorized

users from changing settings.

Connection monitoring

The connections between the device and the external current transformer are continu-

ously monitored. If the device detects a connection error, the CT connection monitoring

alarm will activate, and the contacts will switch over without delay. After the connection

error is cleared, the device will reset based on its latching/non-latching setting.

Restart function

If an alarm is pending after resetting the alarm relay and restarting the system being moni-

tored, this reset process is repeated until the preset number of restart cycles is completed.

As soon as the preset number of restart cycles is completed, the fault memory is set to ON

(latching operation). A manual reset will be required.

Latching capability

The RCM420 has the capability to be set to latch on an alarm and require a manual reset, or

automatically reset when the fault has been cleared. Additionally, the "con" setting allows

for latching, and if a power loss to the RCM420 occurs, it will return to a latched state when

power is restored.

Digital Ground Fault Monitor / Relay

for Grounded AC Systems

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