Electronic Overload Relays Block 3RB12

The following functions are available :-
1. Terminals for the control supply voltage
2. Green “Ready” LED
3. Red “Ground Fault” LED
4. Red “Overload” LED
5. Combined test/reset button with function test
6. 1 NO contact/1 NC contact for overload/ thermistor tripping or NO contact/1 NC contact for overload/ thermistor or ground fault tripping
7. Terminals for thermistor input
8. Terminals for external summation current transformer
9. Terminals for remote or automatic reset
10. Rotary dial for current setting
11. Rotary dial for the trip class
12. 1 NO contact/1 NC contact for ground fault tripping or 1 NO contact/1 NC contact for overload warning
13. Analog output 4 mA … 20 mA

This Electronic Overload Relays Block is easily insert in your schematic diagram and connect as you like way.

The 3RB12 electronic overload relays are designed for the protection of 3- phase and single phase AC loads. If single-phase AC motors are to be protected with the 3RB12 electronic overload relay, the microprocessor only monitors one phase conductor. The main circuits must therefore be connected to the current transformer in accordance with the operating instructions for the 3RB12 electronic overload relay. The 3RB12 electronic overload relays from 0.25 A to 820 A with external power supply are suitable for normal starting and heavy starting with the adjustable setting of the variable tripping classes CLASS 5 to CLASS 30. In addition to the adjustable variable tripping classes, the 3RB12 electronic overload relay offers a large number of additional built-in features and protection functions: overload warning, thermistor-motor protection-function, ground fault detection, self-monitoring, status indicator by means of LEDs, and analog output. More detailed information about the built-in features and functions in section 4.3 “Application and areas of use”. In addition to current dependent protection of loads against non-permissible overheating, the 3RB12 electronic overload relay also offers the possibility for temperature monitoring of the motor windings by use of a Thermistor- (PTC-) sensor circuit. The load can also be protected against excess temperature
that, for example, could appear indirectly due to blocked coolant flow and therefore could not be measured by current dependent means. Further more the 3RB12 electronic overload relay offers the possibility to protect the installation against the results of a ground fault with its internal/ external ground fault monitoring.