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 devices are constructed with complete insulation and can be mounted directly on SIRIUS motor starter protectors, overload relays and current monitoring devices, resulting in a very simple integration into motor feeders.

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.

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
• Wide voltage range for AC control supply voltage

Switching functions

The solid-state contactors for switching motors are "Instantaneous switching", because this method is particularly suited for inductive loads. By distributing the ON point over the entire sine curve of the mains voltage, disturbances are reduced to a minimum.

Connection method

You can choose between the following connection methods for the solid-state contactors for switching motors:

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 mm² can be connected in just one terminal.

Spring-type connection

This innovative technology manages without any screw terminal. This means that very high vibration resistance is achieved. Two conductors of up to 2.5 mm² can be connected to each terminal.

Motor feeders

The devices can use a link module to directly connect to a motor starter protector. Mounting of a 3RB electronic overload relay (see "Protection Equipment") or a 3RR2 current monitoring relay (see "Monitoring and Control Devices") is also supported using a connection adapter. The simultaneous mounting of a circuit breaker and an overload or current monitoring relay is not recommended due to space and temperature rises.

Rapid-switching fuseless and fuse motor feeders can thereby be implemented in a time-saving manner.

Selecting solid-state contactors

The solid-state contactors are selected on the basis of details of the network, the load and the ambient conditions.

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 of the maximum permissible switching frequency based on the characteristic curves (see "More Information" > "Product Information"). 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 frequency, it is possible to achieve an increase by overdimensioning the motor!

Alternatively, the tool for "Selection of solid-state contactors for switching motors" can be used. The correct device size can be determined by entering the network and motor data along with the application and ambient conditions. See https://www.siemens.com/solid-state-switching-devices.

Short-circuit protection

Despite the rugged power semiconductors that are used, solid-state switching devices respond more sensitively to short-circuits in the load feeder. Consequently, special precautions have to be taken against destruction, depending on the type of design.

Siemens generally recommends using SITOR semiconductor fuses. These fuses also provide protection against destruction in the event of a short circuit even when the solid-state contactors and solid-state relays are fully utilized.

Alternatively, if there is lower loading, protection can also be provided by standard fuses or miniature circuit breakers. This protection is achieved by overdimensioning the solid-state switching devices accordingly.

More information

For more information, see

• System Manual "SIRIUS – System Overview", https://support.industry.siemens.com/cs/ww/en/view/60311318
• Manual "SIRIUS – 3RF34 Solid-State Switching Devices", https://support.industry.siemens.com/cs/ww/en/view/60298187

Product information and technical specifications

For product data sheets with detailed technical specifications, dimensional drawings and characteristic curves, see https://support.industry.siemens.com/cs/ww/en/ps/16237.

For additional information, please enter the article number of the required device under the tab "Product List".

Article No. scheme

Note:

The Article No. scheme shows an overview of product versions for better understanding of the logic behind the article numbers.

For your orders please use the article numbers quoted in the selection and ordering data.