UBZ-304 is designed for the protection of asynchronous electric motors with power from 2.5 to 315 kW when using external standard current transformers with an output current of 5 A.

UBZ-304 can operate in networks with both isolated and solidly grounded neutrals.

The device is panel-mounted.

UBZ provides continuous monitoring of network voltage parameters, actual values of phase (line) currents of three-phase electrical equipment 380 V 50 Hz, and checking the insulation resistance of electric motors.

UBZ-304 provides protection for motors in the case of:

– Poor network voltage (unacceptable voltage fluctuations, phase loss, phase sequencing and sticking violations, asymmetry of phase/line voltages, decrease in network frequency below the set value and/or increase in network frequency above the set value);

– Mechanical overloads (symmetrical increase in phase/line currents);

– Exceeding the reverse sequence current threshold;

– Asymmetry of phase currents without overload, related to insulation damage inside the motor and/or power cable (comparison of the current asymmetry coefficient of the reverse sequence with the voltage asymmetry coefficient of the reverse sequence);

– Disappearance of torque on the motor shaft (“dry running” – for pumps) – protection against minimum starting and/or operating current;

– Extended motor start or rotor blocking;

– Unacceptably low insulation resistance between the stator and motor body (pre-check before start-up);

– Stator winding “earth” fault during operation – protection against “earth” leakage currents;

– Thermal overload of the motor;

– Winding overheating (determined by winding temperature when using built-in temperature sensors or casing temperature when using external temperature sensors).

Software

UBZ-304/305 Control Panel – download the program