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Marsh Bellofram Diversified Electronics Division CMI Series AC Over Current Monitor

Marsh Bellofram Diversified Electronics Division CMI Series AC Over Current Monitor

Product catalog summary

Overview: The CMI Series Over Current Monitor Relay is designed to operate in a fail-safe mode, ensuring that the relay is energized when the monitored AC current is within normal limits. It de-energizes when the current exceeds a preset trip point or when control voltage is removed.

Operation: Upon initial current application, a time delay is activated to prevent false tripping due to high inrush currents. This delay is adjustable and should be set longer than the motor's inrush time. If the current exceeds the trip point after the delay, the relay de-energizes and locks out until reset. The relay remains energized if the current normalizes before the delay ends.

Applications: Commonly used for detecting conveyor jam-ups, the device can extend its range with an external current transformer (CT).

Specifications:

Control Voltage: 24 or 120 VAC/VDC, 50/60 Hz
Current Trip Points: Adjustable ranges from 0.05 to 20 amps
Output: DPDT, 10 Amps @ 120 VAC, Resistive
Time Delay: Adjustable from 0.2 to 10 seconds
Operating Time: 50 mSEC after initial delay
Current Withstand: 20 times nominal for 1 second
Isolation: 2500 Volts between input and other terminals
Indicator: Glows on normal current
Reset: Manual via button or control voltage interruption
Temperature Rating: Operate 32° to 131°F (0° to +55°C), Storage -49° to 185°F (-45° to +85°C)
Enclosure: Lexan surface mounted with #8-32 screw terminals
Weight: 11 oz.

Figures: Figures 1 and 2 illustrate the fail-safe detection of motor jam-ups.

Catalog excerpts

Marsh Bellofram Diversified Electronics Division CMI Series AC Over Current Monitor-1

800.727.5646 atcdiversified.com Diversified Electronics CMI Series Current Monitors // CMI Series 243 A C Ov e r C ur r e n t M o n i t or The CMI Series Over Current Monitor Relay operates in the fail-safe mode as the relay is energized (pick-up) when the monitored AC current is normal. The relay de-energizes (Drop-out) when the monitored current rises above the preset trip point or the control voltage is removed. When current is initially applied, a time delay begins. This inhibits the over current sensors while high inrush currents are present. The delay is field adjustable and is set so the delay period is slightly longer than the inrush time of the motor. If the monitored current is above the preset trip point when the delay elapses, the relay de-energizes. (Figure 1) If the current drops to the normal run current of the motor prior to the completion of the delay period, the relay remains energized until the current rises above the trip point, which indicates an abnormal condition. At that time the relay de-energizes and remains lockedout until the reset button is pressed or the control voltage is interrupted, and re-applied. (Figure 2) A typical application is for conveyor jam up detection. An External CT may be used to extend the range of the Current Monitor. MODEL NUMBER >>>>>> CMI A S E Control Voltage 24 .25 24 Volts 120 Volts 120 Current Trip Points 0.05 to 0.25 amps. adj. 0.2 to 1 amps. adj. 1 1.0 to 5.0 amps. adj. 5 2.0 to 10 amps. adj. 10 4.0 to 20 amps. adj. 20 \\\WIRING \\\DIMENSIONS (INCHES) \\\OPERATION \\\SPECIFICATIONS CONTROL VOLTAGE 24 or 120 VAC/VDC, 50/60 Hz TRIP POINTS Pick-up See Order Information Drop-out Press Reset Button or Restore Control Voltage OUTPUT DPDT, 10 Amps @ 120 VAC, Resistive TIME DELAY 0.2 to 10 SEC, Adjustable On Motor Starting OPERATING TIME 50 mSEC (After Initial Delay has Timed Out) CURRENT WITHSTAND 20 Times Nominal for 1 Second ISOLATION 2500 Volts Between Input and All Other Terminals INDICATOR Glows on Normal Current RESET Manual, Press Button or Interrupt Control Voltage RESET TIME 100 mSEC After Lock-Out TEMPERATURE RATING Operate 32° to 131°F (0° to +55°C) Storage -49° to 185°F (-45° to +85°C) ENCLOSURE Lexan Surface Mounted; #8-32 Screw Terminals WEIGHT 11 oz. Figure 1 Figure 2 FAIL SAFE DETECTION OF MOTOR JAM UPS

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