Microprocessor protection system EZAD – M1

1. Applications:

EZAD-M1 is a digital device for protection and work mode control of AC motors 380 V from the whole variety of powers – 0,5 – 300 kW in the electric drives of pumps ventilators, centrifuges, transport conveyors etc. that work during long or short periods of time. EZAD-M1 realizes an exact thermal model during heating and cooling of the electric motors, which is based on standardized thermal limit curves. There is an LCD display a powerful PIC processor with an in-built ADC and standard interface RS 232 allowing connection to other processing devices.

2. Protective functions

EZAD-M1 provides protection to the electric motor and to the production mechanism when:

• overload in an symmetric mode due to not following the technological requirements or due to faults in the electric network. Turning off in this emergency mode can be performed 38 protective curves depending on the heat inertia of the motor and the turning on conditions (class 2 – 40 fig. 1);

• loss of circuit phase with time delay of 2 sec. Three current sensors are needed to realize this emergency mode;
• inadmissible asymmetry in the current system. The coefficient of the admissible asymmetry can be adjusted. Time delay when turning-off is 20 sec.;
• “locked rotor” work mode. Time delay when turning-off is adjustable in the 1-12 sec diapason;
• “underload” work mode. Time delay is adjustable in the 1-600 sec. diapason;

1. Control, warning and communication functions:

EZAD-M1 displays in working mode the following parameters:

• current load Ki = I/In in % or in As for each phase;
• thermal status in graphics; horizontal quadruple segments from 1 to 10 correspond to the calculated engine temperature according to the input thermal mode;
After emergency shutdown the protection unit records and displays failures in Cyrillic:
• "прегряване" - turning off after overloading in symmetry mode;
• "Отп. фаза" - lost of phase;
• "асиметрия" - inadmissible asymmetry in the current system;
• "Мин. Товар" - underload;
• "Заст. ротор" - locked rotor.
When needed the warning function for overloading can be activated after 100 % load of the engine. The operating relay status is controlled through light emitting diode indication (green constantly led diode). There is an interface channel allowing connection with other processing devices and with the rest of the protection system modules.
2. Timer

There is an in-built timer in EZAD-M1 that provides time-delay when starting in automated mode (without a starter) of the electric drive. Time-delay is within the 1 – 600 sec. diapason.

3. Control and parameter adjustment means:

The microprocessor protection system is supplied with 4 control buttons: MODE – choosing variable and mode; UP – increase of the selected variable; DOWN – decrease of the selected variable; RESET – hardware processor reset.
There are two possible work modes: "WORK MODE" and "PROGRAMMING MODE". Selecting "PROGRAMMING MODE" is possible when the engine is stopped. The "UP" and "DOWN"buttons are together activated."SETUP MODE"message is displayed on the display. The following adjustment parameters are sequently selected with the MODE button:

• Inom - nominal primary engine current. Adjustment range:1- 600 A.
• Ktr - current transformers transformation coefficient. Adjustment range: 1-120.
• Class - protection class. Adjustment range: 2 - 40.
• Kimin - adjustment of underloading in % of the predetermined nominal current. Adjustment range: 1-99 %.
• Tmin - time delay in underloading. Adjustment range: 1-600 sec.
• Kasm - adjustment of asymmetry current system. Ajustment range: 5-30%.
• Tn -initial timer time-delay. Adjustment range: 1-600 sec.
• Tsc - time-delay in stall condition mode. Adjustment range: 1-12 sec.
• Com port - interface connection status – active, inactive.
• Amperes - ampermeters status - active, passive. When active status – during work the three phases primary current is indicated in As instead of symmetrical current load in %.
4. Protection reset:

After an emergency shutdown the system can be restarted only if the temperature status is fewer than 50 %. The MODE and RESET buttons are sequently pushed until initial timer is on. After powering voltage is down in the network the emergency status is memorized which allows the servicing personnel to localize the malfunction more easily.

5. Mounting and connection schemes:

The connection of the protective device can be done through the help of 3 current transformers Ix/5A/5W or through current sensors developed by the manufacturer.
Mounting is done on DIN strip according to the manufacturer’s mounting schemes.