Digital overcurrent relay with voltage protection and 3×3-digit LED display TRM-30F

Overcurrent monitoring relay TRM-30F with display, 3-phase up to 25A

It is designed to protect equipment sensitive to operating current and voltage values from faults that may occur due to:

• current overloads (adjustable current value 0.5 ... 30 A)
• current asymmetry (50%, fixed value)
• voltage asymmetry (30%, fixed value)
• overvoltage and undervoltage (Umin: 265 V, Umax: 440 V, fixed value)

The digital overcurrent relay TRM-30F with display allows monitoring the current in each phase and protects the motor or device against overcurrent, overvoltage, undervoltage, phase failure, and phase reversal. These digital overload relays are designed to prevent damage to the motor/load due to high currents while allowing current verification flowing in each phase on the display. They can also check cumulative voltage values between phases.

With two output relays (1x NO, 1x NC), it is also possible to control or disconnect the load when the overcurrent reaches the set value, or to activate a signaling contact for the monitoring system. The digital TRM-xx relays have built-in current transformers and a 3x3-digit display for current indication.

Usage and operating principle

1. Connect the device according to the wiring diagram. Incorrect connections can damage the device.
2. Use the ">A" controller to set the device's overcurrent according to the operating load current you will check.
3. When power is connected, the set overcurrent value is displayed on the top screen and the fault delay time on the middle screen during the first second.
4. After one second of operation, the actual current values from the phases will be displayed and the indicator LED will light up.
5. When you press the "V/A/RESET" button, the combined voltage values between phases are displayed.

Drivers

• "A>" - setting the allowed overload; the value is shown on the top display.
• "sec." (sec.) - setting the delay time for overcurrent fault; the value is shown on the middle display.

Contact status

• NO 95-96, NC 97-98:

• Device de-energized or in fault condition: NO open, NC closed.
• Device energized and without fault: NO open, NC open.

Indicator LED diode

• LED "V" - lights up in case of overvoltage/undervoltage or voltage asymmetry fault.
• LED "A" - lights on high current or current asymmetry fault.
• LED "XI" - lights on incorrect phase sequence.
• LED "NOR" - lights when device is powered and system is fault-free.

Function of button "V/A/RESET"

• Reset: press for 3 seconds clears fault, LED "A" goes off, NO contact closes, NC contact opens.
• V/A: short press switches display between current and voltage values.

Protection and operating principle

1. Overcurrent protection (0.5-30 A):

• Transition to fault state: when set overcurrent is exceeded, wait set time. Phase display flashes, LED "A" lights, NO open, NC closed, LED NOR off.
• Exit fault state: current is below set value, press reset for 3 seconds.

2. Current asymmetry protection:

• Input: current difference between phases >50 %, wait 3 seconds, display flashes, LED "A" lights.
• Output: difference <50 %, press reset for 3 seconds.

3. Overvoltage protection (U>440 V):

• Input: voltage >440 V, wait 3 seconds, display flashes, LED "V" lights.
• Output: voltage <435 V, wait 3 seconds.

4. Undervoltage protection (U<265 V):

• Input: voltage <265 V, wait 3 seconds, display flashes, LED "V" lights.
• Output: voltage >270 V for 3 seconds.

5. Voltage asymmetry protection:

• Input: voltage difference >30 %, waits 3 seconds, display flashes, LED "V" lights.
• Output: difference <30 % for 3 seconds.

6. Phase sequence protection:

• Incorrect phase connection lights LED "XI".

Current asymmetry calculation

Instrument calculates asymmetry according to the formula:

Example: ((25 - 15) / 25) × 100 = 40 % current asymmetry.

Technical specification

• Supply voltage: measured voltage 3f 3x400 VAC
• Operating voltage (Un): 3x380 VAC 50/60 Hz, own power <10 VA
• Adjustable overcurrent (overload): 0.5-30 A
• Fault delay time (t): 0-20 s
• Display: 3x3 digits, 9 mm height, 7 indicator LEDs
• Overvoltage: 440 V (L-L)
• Undervoltage: 265 V (L-L)
• Voltage asymmetry: 30%
• Current asymmetry: 50
• Asymmetry fault delay time: 3 s
• 2x output relays (1x NO, 1x NC): 3 A / 250 V AC (resistive load)
• Connection type: screw terminals
• Cable cross-section: 2.5 mm² (relay contacts) / 6 mm² (input and output loads for measurement)
• Weight: up to 380 g
• Mounting: on DIN rail
• Operating temperature: -20 °C ... +55 °C
• Operating altitude: <2000 m