Shift Controls was approached to design and fabricate a full featured, skid mounted control panel to monitor and control an automated process. The system was complete with a PLC, I/O interfacing, pneumatic solenoid manifold, power monitoring, variable motor drives, power distribution and current protection, touchscreen, slide-out keyboard, and stacklight.
Electrical Requirements
Since the panel was to be skid mounted, it was important to design the power distribution system to have a single power feed for ease of installation and operation. The panel contains all the power distribution, current protection, transformers, and control needed for each load.
The panel is protected by a main circuit breaker with an external disconnect handle. The 3-phase feed voltage and current was measured by a Modbus TCP DIN mount power monitor and reported to the PLC for monitoring, logging, and alarming.
Power is distributed to current limiting fuses and UL489 breakers for the variable speed drives, an in-panel 120 VAC power transformer, control power supply, and an external heater control panel. Breakers with integral ground fault protection were specified for the 120 VAC loads that were to be located in the washdown area to protect the operators and equipment.
Environmental Requirements
The panel was to be installed in a washdown area that would be exposed to high pressure water sprays and cleaners. This required the panel to be made of stainless steel and all external components and connectors to be rated Nema/Type 4X.
To be able to dissipate the large amount of heat produced by the VFDs and other internal components, heat calculations were performed and a large fan, vent, and washdown hoods were specified to ensure the panel's internal temperature did not exceed 50°C and maintained the Nema/Type 4X rating.
The system monitors and controls a large number of networkable field I/O, interlocks, and power components. In order for these systems to be installed and commissioned easily, M12 interfacing connections with color coded labels located on the bottom of the panel were used for all instrumentation and field I/O. The connectors maintained the washdown rating of the panel and allowed all of the field connections to be easily made with industrial standard cabling solutions.
Control Requirements
To start the design process, the client provided a functional specification document for Shift Controls to implement. The document detailed each required component with a tag, manufacturer, model number, communication standard, and power requirements. From this information we were able to design the power distribution, internal networking, bus communications, and specify the M12 connector pin outs. The PLC controlled and monitored the VFDs, power monitor, stacklight, pneumatic solenoid manifold, external I/O and devices though digital communication (TCP Modbus and I/O link). The operator interfaced the PLC with the local door mounted touchscreen and a door mounted slide-out keyboard tray.
The panel also featured a full safety E-Stop system which included a door mounted E-Stop button, external E-Stop dry contact/PNP inputs that would shutdown the system. The system also included external E-Stop alarm dry contacts so other equipment modules would be shutdown in case of an E-Stop condition. All of the E-Stop inputs and outputs were wired to a safety relay module with force guided relay output contacts. The E-Stop safety relay controlled a main E-Stop contactor which would de-energize external power devices in the case of an E-Stop.
Custom Designs
Shift Controls has extensive experience in designing and fabricating custom panels to meet the most difficult design and environmental requirements. Like this project, we provide full design of temperature control, motor control, and PLC/DCS interfacing into our panels. We have extensive experience in industrial controls and process control and can provide turn-key solutions to meet your most challenging design requirements. As always, feel free to contact us regarding your project or if you have any questions.
