The universal motor protection unit UBZ-302-02 is designed for continuous monitoring of mains voltage parameters, current values of phase/line currents of three-phase electrical equipment 400 V, 50 Hz and checking the insulation resistance of electric motors.

UBZ-302-02 provides protection for asynchronous motors with power from 0.25 kW to 3.3 kW when
when using built-in transformers and up to 315 kW when using external current transformers, including in networks with an insulated neutral.

UBZ provides protection for electric motors in the following cases:

• Low-quality mains voltage (unacceptable voltage surges, phase breaks, violations of.
• Alternating and sticking phases, unbalanced line voltages).
• Mechanical overloads (symmetrical overload by phase/line currents).
• Exceeding the reverse sequence current threshold.
• Asymmetry of phase currents without overloading, associated with insulation failure inside the motor or.
• Insulation inside the motor or supply cable (comparison of the reverse current unbalance factor with the reverse voltage unbalance factor).
• Loss of torque on the motor shaft (‘dry running’ - for pumps) - protection by minimum starting and/or operating current.
• Delayed motor start or rotor blockage.
• Unacceptably low level of insulation between the stator and the motor housing (check before switching on).
• Stator winding short-circuiting to earth during operation - earth leakage current protection.
• Thermal overload of the motor.
• Overheating of the windings (the temperature of the windings is determined when using the built-in.
• Temperature sensors or the temperature of the housing when using external temperature sensors).