Overload Relays 3RB2 Solid-State Overload Relays 3RB22, 3RB23 for high-feature applications Overview The modular, solid-state overload relays with external power supply type 3RB22 (with monostable auxiliary contacts) and type 3RB23 (with bistable auxiliary contacts) up to 630 A (up to 820 A possible with a series transformer) have been designed for inverse-time delayed protection of loads with normal and heavy starting (see "Function") against excessive temperature rises due to overload, phase unbalance or phase failure. An overload, phase unbalance or phase failure result in an increase of the motor current beyond the set rated motor current.
This cur- rent rise is detected by means of a current measuring module and electronically evaluated by a special evaluation module which is connected to it. The evaluation electronics sends a si- gnal to the auxiliary contacts. The auxiliary contacts then switch off the load by means of a contactor. The break time depends on the ratio between the tripping current and current setting I e and is stored in the form of a long-term stable tripping characteristic (see "Characteristic Curves") . The "tripped" status is signaled by means of a continuous red " OVERLOAD " LED.
The LED indicates imminent tripping of the relay due to overload, phase unbalance or phase failure by flickering when the limit current has been violated. This warning can also be issued as a signal through auxiliary contacts. In addition to the described inverse-time delayed protection of loads against excessive temperature rises, the 3RB22/3RB23 solid-state overload relays also allow direct temperature moni- toring of the motor windings (full motor protection) by connection with short-circuit and open-circuit detection of a PTC sensor cir- cuit.
With this temperature-dependent protection, the loads can be protected against overheating caused indirectly by reduced coolant flow, for example, which cannot be detected by means of the current alone. In the event of overheating, the devices switch off the contactor, and thus the load, by means of the aux- iliary contacts. The "tripped" status is signaled by means of a continuously illuminated " THERMISTOR " LED.
To also protect the loads against high-resistance short-circuits due to damage to the insulation, humidity, condensed water, etc., the 3RB22/3RB23 solid-state overload relays offer the pos- sibility of internal ground-fault detection in conjunction with a function expansion module ( for details see Catalog LV 1, "Selection and ordering data"; not possible in conjunction with contactor assembly for wye-delta starting). In the event of a ground fault the 3RB22/3RB23 relays trip. The "tripped" status is signaled by means of a continuous red " GND FAULT " LED. Signal- ing through auxiliary contacts is also possible.
After tripping due to overload, phase unbalance, phase failure, thermistor or ground-fault tripping, the relay is reset manually or automatically after the recovery time has elapsed (see "Function") . In conjunction with a function expansion module the motor cur- rent measured by the microprocessor can be output in the form of an analog signal 4 ... 20 mA DC for operating rotary coil in- struments or for feeding into analog inputs of programmable logic controllers. With an additional AS-Interface analog module the current values can also be transferred over the AS-i bus system.
The devices are manufactured in accordance with environmen- tal guidelines and contain environmentally friendly and reusable materials. They comply with all important worldwide standards and approvals. 1 2 9 3 5 4 6 5 7 8 3RB22/3RB23 evaluation module (1)Green "READY" LED: A continuous green light signals that the device is working correctly. (2)Red "GND FAULT" LED A continuous red light signals a ground-fault tripping. (3)Red "THERMISTOR" LED: A continuous red light signals an active thermistor trip. (4)Red "OVERLOAD" LED: A continuous red light signals an active overload trip; a flickering red light signals an imminent trip (overload warning). (5)Motor current and trip class setting:
Setting the device to the motor current and to the required trip class dependent on the start-up conditions is easy with the two rotary switches. (6)Selector switch for manual/automatic RESET: With this switch you can choose between manual and automatic RESET. (7)TEST/RESET button: Enables testing of all important device components and functions, plus resetting of the device after a trip when manual RESET is selected. (8)Connecting terminals (removable joint block): The generously sized terminals permit connection of two conductors with different cross-sections for the auxiliary, control and sensor cir- cuits.
Connection is possible with screw connection and alternatively with spring-type connection. (9)3RB29 85 function expansion module: Enables more functions to be added, e. g. internal ground-fault detec- tion and/or an analog output with corresponding signals. 3RB29 06 current measuring module 29 Siemens · 2009