The UBZ-301 universal electromotor protection unit belongs to the new generation of electromotor protection devices. Application of modern microprocessor-based technology allows to provide the necessary unit operation logic that no protection devices of domestic and foreign production can support. The UBZ is a conceptually new reasonably-priced device that provides full and effective multi-fault protection (protection from all faults in the mains, motor performance-induced faults and internal fault conditions of motor) for 3-Phase AC motors by a magnetic starter (contactor) coil control. The unit is designed for the continuous monitoring of the mains voltage parameters and for RMS phase/line currents of 3-Phase AC 380V/50Hz electrical equipment monitoring, primarily, of induction motors that develop power from 2.5kWT up to 315 kWt, isolated neutral system included. It offers a solution for an electric motor heat balance equation.
There are three separate modifications of the UBZ that cover three nominal current ranges:
UBZ-301 5-50A;
UBZ-301 10-100A;
UBZ-301 63-630A.
The unit isolates electrical equipment from the running system and/or disables its start:
- when the mains voltage is of poor quality (unallowable voltage jumps, phase loss, incorrect phase sequence and phase «coincidence», phase/line voltage imbalance);
- when mechanical overloads (symmetrical phase/line current overload) take place. The unit performs overload protection with a dependent time delay;
- when phase/line current asymmetrical overloads induced by faults inside the motor occur. The unit performs protection from phase current imbalance and further disables an automatic reset;
- when phase current asymmetry without overload occurs that is induced by the insulation fault inside the motor and/or the power cable;
- when motor load is lost ( « dry stroke » for pumps). The unit provides the minimum start and/or operating current protection;
- when insulation level to frame is abnormally low. The unit performs insulation level test before start and if the insulation is poor the start is disabled.
- when stator winding ground-to-fault occurs during operation. The unit performs the ground leakage current protection.
THE UBZ-301 PROVIDES:
- a simple and accurate electromotor nominal current setting by nominal current standard scale;
- the electromotor operating current setting that differs from standard values;
- overload tripping with a dependent time delay (the current-time characteristic curve is plotted for a conventionally cold motor). The motor heat balance differential equation is being solved in the operation process. This approach enables to take account of the preceding electromotor status and to make a decision on heat overload presence with the maximum validity. This method also permits to allow for a motor start heating and to restrict (at the customer’s option) amount of starts per unit time;
- shift of current-time characteristic curve along the current-axis and along time-axis as well;
- setting of trip thresholds for the minimum/the maximum voltage, line voltage & phase current imbalance, and also for automatic reset delay at the personal customer’s discretion;
- fault type indication, the mains voltage presence indication, current range indication the unit is adjusted to, and load energization indication;
- the data exchange and transfer to the local computer network according to the RS-485 MODBUS record through the BO-01 exchange unit (BO-01 is supplied on order).
FEATURES
- the unit is a microprocessor-based digital device;
- a high degree of reliability and accuracy is provided;
- the unit doesn’t need any auxiliary supply because it retrieves it's energy demand out of the measurement signal: it’s self-powered by the voltage to be monitored;
- simultaneous isolated independent monitoring for the mains voltage and phase currents permits to detect the type of occurring fault and to provide a different decision-making logic for each fault type;
- when the mains voltage faults occur the unit performs automatic load reset on return voltage parameters to normal operating conditions;
- if a fault is induced by abnormal condition inside the motor (phase current imbalance at the symmetrical power line voltage, leakage current presence etc.) restart is disabled;
- when the unit trips, the load is de-energized by a break in the magnetic starter coil power circuit;
- nominal parameters and trip thresholds are set by front-panel screwdriver potentiometers;
- the unit provides an insulation level monitoring;
- when phase current imbalance (in %) is twice exceeds voltage imbalance the automatic reset is forbidden and the unit is disabled;
- nominal currents setting is to be performed correcting for load connections (Wye/Delta), ‘cause currents are measured by toroidal current transducers which are put on the load power leads. When the load connection is Wye, the currents correspond to the load phase currents. When load connection is Delta, the load phase currents are 1.73 times less than the currents that flow through power leads;
- the motor is protected from the heat overload; after the load has been de-energized owing to the heat overload it will automatically be energized again:
- according to heat hysteresis if time delay Ton=0, i. e. the motor must cool down 30% of the stored up heat;
- according time delay Ton if Ton>0;
- by suitable selection of different Ton values, heat hysteresis considered, one can reduce number of starts per time unit because in the intermittent cycle the unit stores heat quantity released at the start of the motor;
- the unit produced is completely ready for operation and needs no special pre-starting procedure measures;
- owing to digital technology all the unit settings are aligned quite accurate, so no control devices are needed to adjust them.
