Universal Motor Protection Unit UBZ-301 (hereinafter referred to as the unit) is designed for continuous monitoring of network voltage parameters and actual phase/line current values of three-phase electrical equipment 380 V / 50 Hz, primarily asynchronous electric motors (EM), with a power range from 2.5 kW to 315 kW, including networks with an isolated neutral.

Three modifications of the device are produced based on current ratings:

• UBZ-301 5-50A;
• UBZ-301 10-100A;
• UBZ-301 63-630A;

    Provides complete and effective protection of electrical equipment by disconnecting from the network and/or blocking its start in the following cases:

• Poor network voltage (unacceptable voltage surges, phase breaks, phase sequence violations, phase sticking, phase/line voltage imbalances);
• Mechanical overloads (symmetrical overloads by phase/line currents) - protection against overload with a dependent time delay;
• Asymmetrical overloads by phase/line currents associated with internal damage to the motor - protection against phase current imbalances with subsequent prohibition of automatic reclosing;
• Phase current asymmetry without overload associated with insulation failure inside the motor and/or the supply cable;
• Loss of torque on the EM shaft ("dry run" - for pumps) - protection by minimum starting and/or operating current;
• Unacceptably low insulation levels to the body - pre-start check with start blocking for poor insulation;
• Ground fault in the stator winding during operation - protection by leakage currents to "ground".

The unit provides protection of electrical equipment by controlling the magnetic starter (contactor) coil.

Performs the following functions:

• Simple and accurate setting of the rated current of the EM using a standard scale of rated currents;
• Setting the operating current of the EM different from standard values, considering permissible long-term overload;
• Operation under overload with a dependent time delay. The current-time characteristic is built for a conditionally cold engine. During operation, the differential equation of the EM thermal balance is solved. This approach allows taking into account the previous state of the EM and most reliably deciding on the presence of thermal overload. This method also allows considering EM heating during starts and limiting (at the request of the customer) their number per unit of time;
• Ability to shift the current-time characteristic along both the current and time axes;
• Setting trip thresholds for minimum/maximum voltage, line voltage imbalance, and phase currents, as well as automatic reclosing time, at the customer's discretion;
• Indication of the type of accident, the presence of network voltage, the current range to which the unit is set, and the load connection;
• Via the BO-01 exchange unit, it allows for information exchange and transmission via the RS-485 protocol (BO-01 is supplied on order).