Solid-State Switching Devices for Switching Motors Solid-State Contactors General data ■ Overview ■ Design Load feeders There is no typical design of a load feeder with solid-state relays or solid-state contactors; instead, the great variety of connection methods and control voltages offers universal application oppor- tunities. SIRIUS solid-state relays and solid-state contactors can be installed in fuseless or fused feeders, as required. There are special versions with which it is even possible to achieve short- circuit strength in a fuseless design. Mounting regulations >70 (2,75) >20 (0,8) >20 (0,8) >20 (0,8) 3RF24.. 3RF24..
Solid-state contactors for switching motors The solid-state contactors for switching motors are intended for frequently switching on and off three-phase current operating mechanisms up to 7.5 kW and reversing up to 3.0 kW. The de- vices are constructed with complete insulation and can be mounted directly on circuit breakers and SIRIUS overload relays, resulting in a very simple integration into motor feeders. >50 (2) NSB0_01814 These three-phase solid-state contactors are equipped with a two-phase control which is particularly suitable for typical motor current circuits without connecting to the neutral conductor. Clearances for stand-alone installation Connection methods Important features:
• Insulated enclosure with integrated heat sink • Degree of protection IP20 • Integrated mounting foot to snap on a standard mounting rail or for assembly onto a support plate • Variety of connection methods • Plug-in control connection • Display via LEDs All SIRIUS solid-state switching devices are characterized by the great variance of connection methods. You can choose between the following connection methods: Screw connection The screw connection system is the standard among industrial controls. Open terminals and a plus-minus screw are just two features of this technology. Two conductors of up to 6 mmІ can be connected in just one terminal.
As a result, loads of up to 50 A can be connected. Spring-type terminals Selecting solid-state contactors The solid-state contactors are selected on the basis of details of the network, the load and the ambient conditions. As the solid- state contactors are already equipped with an optimally mat- ched heat sink, the selection process is considerably simpler than that for solid-state relays. This innovative technology manages without any screw connec- tion. This means that very high vibration resistance is achieved. Two conductors of up to 2.5 mmІ can be connected to each ter- minal. As a result, loads of up to 20 A can be dealt with. The following procedure is recommended:
• Determine the rated current of the load and the mains voltage • Select a solid-state contactor with the same or higher rated current than the load • Testing the maximum permissible switching frequency based on the characteristic curves (see pages 58 and 64) . To do this, the starting current, the starting time and the motor loaded in in the operating phase must be known. • If the permissible switching frequency is under the desired fre- quency, it is possible to achieve an increase by overdimensio- ning the motor! 53 Siemens · 2009