Microprocessor short circuit protection system EZAD-MT

1. Application:

EZAD-MT is a digital device for short circuit protection of the start-up equipment in the electric drives of AC motors 6kV. When any of the predetermined values for the motor current is exceeded, the device turns off the motor with 50 ms time delay. When the device is activated the values of the three linear currents are memorized thus making it easier for the servicing personnel to localize the malfunction. When the EZAD-MT is working it indicates the three linear currents thus providing motor’s loading visualization. For the full protection it is referred to use the EZAD-MT in combination with the base protection module EZAD-M1.

2. Protective functions:

EZAD-MT supplies protection of the start-up equipment, the powering circuit and the transformer when short circuit occurs.

3. Light and digital indications:

The EZAD-MT monitoring and displays the following parameters:

• the current of the three linear conductors in As with the help of 7 segments with light emitting indicators;
• the current line’s current shown on the display(Ir, Is, It);
• condition of the operating relay (READY) indicated with a green light emitting diode: when there is a operational circuit is lid when the circuit is opened – is not lid;
• - the connection of power disconnector is indicated by two diodes – ON (green) when turned on and OFF (red) when turned off or lack of power in the circuit;
• - the control and adjustment parameters.
4. Control and adjustment parameters:

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 motor is stopped. Then the 000 indication of the current is written on the display. The UP and DOWN buttons are together activated. The display is turned off after pushing the buttons the KXX sign is written on it. The K index codes the adjustment variable and XX numbers show the entered adjustment parameter. The following variables are sequently chosen through the MODE button:

• / /- nominal primary current of the motor In. The adjustment range is – 1-100 A;
• / /- transformation coefficient of the current transformers Ktr. The adjustment range is – 1-20;
• / /- short circuit multiplicity coefficient Ki=Ikc/In. The adjustment range is – 8-12.
After the consecutive activation of the MODE button the protection system starts the “WORK MODE”. When engine is stopped (Ready and Off are lid) the display reads 000. The diodes “It”, “Is”, “Ir” are not lid. After engine start-up “On” is lid and “Off” – not lid. The yellow diode “It” is also lid, which shows that on the display is shown the present value in “T” phase. The current choice in the different phases is done with the MODE, UP and DOWN buttons.
5. Protection system status in a post-emergency mode. Current shortage account and reset:

The ON and READY diodes are not lid after emergency shutdown of the engine and the OFF diode is the only one left lid. The screen shows only the zero value of the current – engine shutdown. The shortage values check up is done by a consequent push of the MODE button while the yellow diodes show the controlled phase.
After eliminating the malfunction causes, the protection system is put into a stand by mode by pushing the "RESET" button. The "READY" diode is lid. The nullifying of the registries accounted for the emergency values of the current is done by a compulsory entering a "SET UP" mode.

6. Mounting:

The connection of the protective device is done only by an applied mounting scheme granted by the manufacturer. Only use current transformers purposed for protection (saturation coefficient > 12).

NOTA BENE IT IS VERY IMPORTANT TO USE 3 CURRENT TRANSFORMERS PURPOSED FOR PROTECTION - ONE IN EVERY PROTECTED PHASE!

The mounting is to be done on a DIN-strip.