Universal electric motor protection unit UBZ-301
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The universal motor protection unit UBZ-301 10100A (hereafter the unit) is designed to supervise the mains voltage parameters and RMS phase/line currents of three-phase electrical equipment 380V/50Hz, first and foremost of asynchronous electromotors (EM) having power range within 5kWt -- 50 kWt, isolated neutral systems included.
The UBZ-301 provides full and effective protection of electrical equipment due to its stop and/or its start disabling in cases as follows:
when the mains voltage is of poor quality (abnormal voltage jumps, phase failure, phase sequence and phase coincidence faults, phase/line voltage imbalance) ;
when mechanical overloads (symmetrical phase/line current overload) occur - the unit provides protection against overload with a dependent time delay;
when phase/line current asymmetrical overloads induced by faults inside motor occur - the unit protects against phase current imbalance and further disables an automatic reset;
when phase current asymmetry without overloads occurs due to insulation fault inside motor and/or service cable;
when motor load is lost ("dry stroke" for pumps) - the unit provides protection against the minimum start current and/or the minimum operating current;
when insulation level to frame is abnormally low - the unit performs test for the poor insulated condition prior to start and if that's the case it disables start;
when stator winding ground-to-fault occurs during operation - the unit provides current protection against ground leakage.
The unit provides electrical equipment protection by magnetic starter (contactor) coil control. The unit offering the following services permits:
to set electromotor nominal current simply and precisely by using nominal current standard scale (see tab. No1) ;
to set electromotor operating current which is other than standard values considering sustained maximum safe overloads;
to trip for overload with a dependent time delay.
This method also permits to take into account an electromotor start heating and to restrict (at the customer's option) amount of starts per unit time;
to shift current-time characteristic curve not only along the current-axis (potentiometers NoNo 1,2) but also along time-axis (potentiometers No 3 - double overload trip delay) ;
to set trip thresholds for the minimum/the maximum voltage, line voltage imbalance and phase current imbalance, and also for reset delay at the customer's discretion on his own;
to indicate type of failure, the mains voltage presence, current range the unit is adjusted to, and load energization;
to exchange and to transfer information according to the RS-485 record through the exchange unit BO-01 (BO-01 is supplied on order) .