Numerical Motor Protection Relay UBZ-304

(1 customer review)


Display: 4 line backlit LCD, Power (Watts or HP): 2.5 – 315 kW (4 – 500 HP), Motor Rated Current: 5A – 630A AC, Motor Voltage: 380 – 415 V AC, Output relay: Power – DPDT (2NO + 2NC) & Programmable – SPDT (1NO + 1NC), Application: Three phase LT motor protection, Communication: RS485 Modbus/ASCII & RS232. Country of Origin: India

18 in stock

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UBZ-304 Three Phase numeric electric motor protection device is designed for protection of asynchronous LT motors having power of 2.5 to 315 kW (5A – 630A), with use of external standard current transformers having output current of 5 amperes (secondary), works in power mains with isolated neural or with solidly grounded neutral terminals.

The device provides continuous monitoring of the mains voltage parameters and RMS phase/line currents of the three-phase electric equipment of 380V-415V 50Hz, as well as for the motor insulation resistance test. More than 90 parameters can be programmed/customized depending on application & usage with variable trip delay and auto-reset delays. Four line full function backlit LCD display provides all information and eases programming from front panel. Built In RS-232 & RS-485 Modbus communication for DCS/ SCADA integration, real time monitoring, programming and remote control. Device comes with free PC software for real time monitoring & programming. Universally accepted flush mounted 96 x 96 x 78.3mm overall dimensions.

UBZ performs the following protection types for electric motors:

  • over-current protection in phases;
  • ground fault protection (zero-sequence current);
  • phase current asymmetry (negative-sequence current);
  • for exceeding negative-sequence current factor to negative-sequence voltage factor;
  • thermal overload;
  • undercurrent protection in phases (dry-run);
  • delayed starting (rotor blocking);
  • overheating of windings (RTD inputs);
  • minimum line voltage;
  • maximum line voltage;
  • line voltage imbalance (negative sequence voltage protection);
  • improper phase sequence;
  • decreasing of mains frequency lower that setting;
  • for increasing of mains frequency higher that setting;
  • minimum insulation resistance of the motor winding;
  • motor phase loss (protection is operated when the motor current is disabled in one (two) phase).

For each type of protection, it is possible to permit and prohibit the load automatic reset. The unit provides for electric equipment protection by means of a magnetic starter (contactor) coil control.

The unit determines load currents when the load relay is open with the open load and programmable relays in the star-delta mode). In this case, the unit shall indicate the fault of an external contactor, which is starting the motor until unit deactivation.


  • control and parameters transfer via RS-485 interface according to MODBUS/ASCII protocol
  • control and parameters transfer via RS-232 interface

Additional Information:


Additional information

Weight 0.350 kg
Dimensions 9.6 × 9.6 × 7.8 cm




Country of Origin


1 review for Numerical Motor Protection Relay UBZ-304

  1. Debasish Ghosh

    It’s the best value motor protection solution for LT motors. I have not seen anything better in this price range.

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