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

Intended to protect the device sensitive to operating current and voltage values from faults that can caused by:

• overcurrent overload (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)

Digital overcurrent overload relay TRM-30F with the display allows showing the current in each phase and protects the motor or consumer from overcurrent, overvoltage, undervoltage, phase loss, and phase sequence changes phase. These digital protective relays are designed to prevent motor/load damage by high currents, while allowing control current flowing in each phase on the display. They can also monitor phase-to-phase voltage values.

Thanks to two output relays (1x NO, 1x NC) it is can also control or disconnect the load when the set overcurrent value is reached, or activate the signal contact in the control system. TRM-xx digital relays have built-in current transformers and a 3x3-digit display for showing current.

Usage and operating principle

1. Connect the device according to the wiring diagram. Incorrect connection may damage the device.
2. Set the device overcurrent value using the controls ">A" according to the operating load current you will monitor.
3. After power-on, during the first seconds on the top display show the set overcurrent value and on on the middle display the error waiting time.
4. Current phase currents are displayed after one second of operation, the indicator LED will light up.
5. By pressing the "V/A/RESET" button display the values of the phase-to-phase voltage.

Controls

• "A>" – setting the allowed overload; the value is displayed on the top display.
• "sec." – setting the error waiting time overcurrent; the value is displayed on the middle display.

Contact status

• NO 95-96, NC 97-98:

• Device without power or in error state: NO open, NC closed.
• Device powered and without faults: NO closed, NC open.

Indicator LEDs

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

Button functions "V/A/RESET"

• Reset: press 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.

Protections and operating principle

1. Overcurrent protection (0.5–30 A):

• Entering fault state: at exceeding set overload current waits set time. Phase display blinks, LED "A" lights, NO open, NC closed, LED NOR off.
• Exit fault state: current below set value, press reset 3 seconds.

2. Current asymmetry protection:

• Entry: current difference between phases >50 %, waits 3 seconds, display blinks, LED "A" lights.
• Exit: difference <50 %, press reset 3 seconds.

3. Overvoltage protection (U>440 V):

• Entry: voltage >440 V, waits 3 seconds, display blinks, LED "V" lights.
• Exit: voltage <435 V for 3 seconds.

4. Undervoltage protection (U<265 V):

• Entry: voltage <265 V, waits 3 seconds, display blinks, LED "V" lights.
• Exit: voltage >270 V for 3 seconds.

5. Voltage asymmetry protection:

• Entry: voltage difference >30 %, waits 3 seconds, display blinks, LED "V" lights.
• Exit: difference <30 % for 3 seconds.

6. Phase sequence protection:

• Incorrect phase sequence lights LED "XI".

Current asymmetry calculation

The device calculates asymmetry according to the formula:

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

Technical specifications

• Power supply: measured voltage 3f 3x400 VAC
• Operating voltage (Un): 3x380 V AC 50/60 Hz, Own consumption <10 VA
• Adjustable overload current: 0.5–30 A
• Fault delay time (t): 0–20 s
• Display: 3x3 digits, height 9 mm, 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 load for measurement)
• Weight: max. 380 g
• Mounting: on DIN rail
• Operating temperature: -20°C … +55°C
• Operating altitude: <2000 m