S801 vs S811 Soft Starters

Both Eaton S801+ and Eaton S811+ industrial soft starters, products of Eaton’s electrical business are very compact and smart electronic devices to smoothly start three-phase induction motors. Both share many common features and are distinct slightly from each other. This article focuses on some of their major characteristics which could be related to their power or control actions, hardware features, and/or environmental specifications with reference to applications, and outlines all similarities as well as differences.

Size and Retrofitting

Both soft starters S801+ and S811 are very compact so they could be retrofitted in existing wye-delta starters, NEMA (National Electrical Manufacturers Association) and IEC (International Electrotechnical Commission) starters, or other soft starters. As this feature of S801+ and S811+ starters makes replacement of the whole system or structure avoidable, so huge expenses are emitted. This feature makes these soft starters more usable and demanding.

Power Wiring

Eaton Corporation recommends connecting line and motor wiring in accordance with local and national codes when S801+ or S811+ starters are used. Anyhow, there exists a little variation between the wiring of these two soft starters. S801+ starters are designed to be wired in an in-line configuration. On the other hand, S811+ starters can be wired in inside-the-delta or in-line configuration. With the type of operational parameters and rating change.

Users can switch between Inline and Inside the Delta configurations by making an appropriate choice from the Config menu (configuration menu) from the soft start user interface (UI). User must take into consideration that FLA (Full Load Amperes) parameter range changes as the operator changes wiring configuration from Inline to Inside the Delta or vice versa (FLA range is higher for Inside the Delta configuration for all S811+ units than that of Inline configuration units when rest of the system and settings remain same). For S811+ soft starter, ‘0’ configures starter for Inline wiring, and ‘1’ for Inside the Delta wiring. In S811+ units, if the pump start and Inside the Delta options are selected simultaneously then configuration changes can’t be made.

By default, both types of soft starters come in the ABC phase sequence on the input power side and the motor must be connected while considering this phase sequence. And if the motor rotates in the incorrect direction, then any two phases from the output terminals of S801+ or S811+ can be exchanged, or that from the motor terminal box.

Control Wiring

To activate the control block in both S801+ and S811+ soft starters, control block supply connection must be given 24V DC nominally (though, control block performs well in the range of 21.6V to 26.4V) and it is to be done before line voltages are supplied. To make a control circuit, the S801+ soft starter has one RJ45 connector and one 12-pin connector. S811+ soft starter also has one screw terminal connector apart from one RJ45 connector and one 12-position connector like S801+.

For both S801+ and S811+ starters, the A12 position connector of Control Terminal Block is used to get 24VDC power for the controller, auxiliary relay functions, and commands relating to soft starter control functions. To make control wiring, S801+ is connected through one RJ12 connector and one terminal block lying in the front of the unit. But in the case of S811+, one RJ12 connector and two terminal blocks are used which are placed in front of the unit.

Network Connections

A3 position screw connector in S811+ is used from Network Communication Terminal Block so as to make any network connections including ModBus connection. But in the case of the S801+ soft starter, the A3 position screw connector is reserved for factory use only and not for any specific operations that could be selected and adjusted by the user of the machine.

As far as User Interface (UI) Module terminal block is concerned, an RJ12 connection is used for connection to the CIM (Control Interface Module) in S801+. This interface can be used to configure the device or to evaluate fault codes for the purpose of troubleshooting. In 811+ soft starters, an RJ12 connection is made use of for making a connection to CIM (Control Interface Module) or DIM (Digital Interface Module). DIM not only allows configuration of a device, evaluation of fault codes for troubleshooting but also allows users to read and write system parameters which makes this product more user-friendly and more programmable.

Control Module is equipped with some DIP (Dual in-line Package) switches. In S801+ starters, switches S2 and 32-1 are not functional. While this is not the situation in the case of S811+ starters. In S811+ starters, switch S2 is to configure remote Communication port. Upon power-up (by 24VDC), it detects a position of the switch and configures Modbus connection at ON position and QCPort at OFF position.

Standards and Certifications

Both S801+ and S811+ soft starters are designed to comply with a range of standards. Some of the standards and certifications pertaining to their functionality and operation include UL 508, CSA 22.2-14-1995, IEC 60947 – 4 – 2, and CC GB14048. Both starters also conform to many CE (Conformité Européenne) and EMC (Electromagnetic Compatibility) standards relating to Electrostatic discharge, electromagnetic field, fast transient bursts, surges, conducted Radio Frequency (RF), 50Hz magnetic field, voltage dip interrupts, radiated emissions, and conducted emissions.   

Key Technology

The purpose of a soft starter is to smooth start a three-phase motor. Both Eaton’s S801+ and S811+ soft starters are intended for an electrical and mechanical smooth start. The basic electronic circuit of both starters is also the same as they have six SCRs (Silicon Controlled Rectifiers) which are connected in a full-wave bridge configuration manner. Through gate channels, the conduction period of these SCRs is controlled to vary the applied voltage to the motor and, thus, its torque in turn. Once the motor gains its desired speed, SCRs are bypassed upon closure of internal contacts.

Fault Warning

Fault warning refers to a feature associated with electronic devices whereupon detection of a fault, a notification is issued or some indication is made while the device keeps operating if the specified parameter is still in safe operational range. Eaton’s S811+ soft starter can be given configuration and protection parameters and made to issue warnings upon detection of an anomaly in operation. Afterward, a warning is displayed on Digital Interface Module (DIM).

For a large number of faults, S811+ soft starter enlists fault warning alongside fault trip and disable like for firmware incompatibility, Pole Overtemp, etc. But there are some severe faults that do not have fault warning options like internal common fault or SCR overcurrent. On the other hand, this feature of fault warning is not available for S801+ soft starter packaging. These units directly trip for severe or non-severe faults as some parameter goes out of the specified range.

Pump Control Option

Both Eaton’s S801+ and S811+ can be used for industrial applications where pumps or chillers are used but S801+ does not incorporate the smart pump algorithm option. Anyhow, the S811+ soft starter has this unique feature that helps prolong the life of all hardware components including motor, pipes, and valves. This control algorithm keeps the motor from experiencing the water hammer effect which occurs due to sudden backflow of water upon stopping the motor. The pump control option of S811+ resolves this issue by ‘Soft Stopping’ the motor. As mentioned in the previous section that motor bypass contactors get closed after soft starting is achieved and the motor has gained its nominal speed. To achieve complete pump control action at a stoppage, in the same way, bypass contactors are opened again upon stoppage of the motor. This action ensures that the motor would be stopped gradually in a tapered manner, avoiding the backflow of water. S801+ soft starter gives its user liberty to set start and stop ramp times according to one’s application requirements. This specification is also associated with an extended ramp or long ramp functionality which helps machine operators have more control over starting and stopping of the motor.

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