MCC Panels

Soft Starters in Custom Engineered Panel

Soft Starters selection, integration, and best practices for Custom Engineered Panel assemblies compliant with IEC 61439.

Soft Starters in Custom Engineered Panel

Overview

Soft starters in a custom engineered panel are used to reduce motor inrush current, limit starting torque, and minimize mechanical stress on pumps, fans, compressors, conveyors, and process mixers. In IEC 61439-2 assemblies, the soft starter is not selected in isolation; it must be coordinated with the busbar system, incoming protective device, enclosure thermal performance, and the load profile of the driven motor. Typical implementations use a 3-phase soft starter with integrated or external bypass contactor, motor rating from a few kilowatts up to several hundred kilowatts, and operational current from 9 A to more than 1000 A depending on frame size and duty class. In custom engineered panels, this is especially important when multiple motor feeders, PLC I/O, VFDs, MCCBs, ACB incomers, and protection relays share the same enclosure. Component selection begins with motor full-load current, starting frequency, acceleration time, load inertia, and allowable voltage dip. For demanding applications, engineers should verify the soft starter’s current rating, overload class, and starting duty cycle against the motor service factor and ambient conditions. Coordination with upstream protection devices such as MCCBs or ACBs must comply with IEC 60947-2 and IEC 60947-4-2, while the complete assembly must satisfy IEC 61439-1 and IEC 61439-2 verification requirements for temperature rise, dielectric strength, short-circuit withstand, and protective circuit integrity. Where the panel interfaces with field equipment, communications via Modbus RTU, Modbus TCP, Profibus, or Ethernet/IP may be included for SCADA or BMS integration. Thermal management is a critical design issue. Soft starters dissipate heat during acceleration and, depending on design, during continuous operation if bypass is not used. Panel builders often specify forced ventilation, filtered fans, thermostats, heat exchangers, or increased enclosure size to maintain internal temperature within component limits. This is particularly relevant in compact wall-mounted enclosures or free-standing custom engineered panels with high packing density. If the panel is installed in hazardous areas or near combustible atmospheres, relevant protections and certifications may also need consideration under IEC 60079, while arc fault and internal fault mitigation may require design attention in line with IEC/TR 61641. Form of separation, cable routing, and segregation between power and control circuits also influence reliability and maintainability. In custom engineered panels, soft starters may be arranged in IEC 61439 Forms 1 to 4 depending on access, service continuity, and maintenance strategy. Bypass contactors, motor protection relays, surge suppressors, and terminal groups are selected to match the application and to support safe commissioning and troubleshooting. Patrion, based in Turkey, designs and manufactures these assemblies for OEM machinery, water treatment, HVAC, oil and gas skids, and industrial utility systems where controlled motor starting and robust panel integration are required. The result is a compact, standards-compliant solution with predictable starting performance, reduced mechanical wear, and reliable long-term operation.

Key Features

  • Soft Starters rated for Custom Engineered Panel operating conditions
  • IEC 61439 compliant integration and coordination
  • Thermal management within panel enclosure limits
  • Communication-ready for SCADA/BMS integration
  • Coordination with upstream and downstream protection devices

Specifications

PropertyValue
Panel TypeCustom Engineered Panel
ComponentSoft Starters
StandardIEC 61439-2
IntegrationType-tested coordination

Other Components for Custom Engineered Panel

Air Circuit Breakers (ACB)

Main incoming/outgoing protection, 630A–6300A, draw-out mounting

Moulded Case Circuit Breakers (MCCB)

Branch protection 16A–1600A, thermal-magnetic or electronic trip

Variable Frequency Drives (VFD)

Motor speed control, energy savings, 0.37kW–500kW+

PLCs & I/O Modules

Programmable logic controllers, remote I/O, fieldbus communication

Contactors & Motor Starters

DOL/star-delta/reversing starters, overload relays, Type 2 coordination

Capacitor Banks & Reactors

Power factor correction, detuned reactors, thyristor switching

Metering & Power Analyzers

Energy meters, power quality analyzers, CT/VT, communication gateways

Surge Protection Devices (SPD)

Type 1/2/3 surge arresters, coordination, monitoring

Busbar Systems

Copper/aluminum busbars, busbar supports, tap-off units

HMI & SCADA Systems

Touch panels, visualization, remote monitoring, data logging

Protection Relays

Overcurrent, earth fault, differential, generator protection relays

Other Panels Using Soft Starters

Motor Control Center (MCC)

Centralized motor control with starters, contactors, overloads, and VFDs in standardized withdrawable/fixed functional units.

Soft Starter Panel

Enclosed soft starter assemblies for reduced voltage motor starting with torque control, ramp-up/down profiles, and bypass contactor options.

Frequently Asked Questions

Sizing starts with the motor full-load current, starting torque requirement, and number of starts per hour. The soft starter must be rated for the motor current at the installation ambient and enclosure temperature, not just the nameplate rating. For high-inertia loads, select a device with sufficient overload class and thermal capacity, and verify that the duty cycle does not exceed the manufacturer’s limits. In an IEC 61439-2 panel, the selected unit must also fit the assembly’s temperature-rise budget and short-circuit coordination scheme with upstream MCCBs or ACBs to IEC 60947-2.
A bypass contactor is strongly recommended for most fixed-speed motor applications because it reduces heat dissipation after acceleration and improves efficiency. In a custom engineered panel, the bypass contactor is typically coordinated with the soft starter’s internal control logic or external control terminals, and selected per IEC 60947-4-1/4-2 duties. If the motor runs frequently or continuously, bypass also helps preserve the panel’s thermal margin, especially in compact IEC 61439 assemblies with multiple feeders, PLC power supplies, and communication modules.
The panel assembly itself is designed and verified to IEC 61439-1 and IEC 61439-2, covering temperature rise, dielectric properties, clearances, creepage, and short-circuit withstand. The soft starter and associated switching/protection devices are commonly evaluated under IEC 60947-4-2 and IEC 60947-2 for coordination with MCCBs or ACBs. If the panel is used in a hazardous location, IEC 60079 may apply. For internal fault containment expectations, IEC/TR 61641 is often considered during design of larger low-voltage switchboard and motor control center style assemblies.
Yes. Many modern soft starters provide communication options such as Modbus RTU, Modbus TCP, Profibus, or Ethernet-based protocols for status, fault codes, current, torque, and start/stop commands. In a custom engineered panel, this allows integration into SCADA or BMS systems for remote monitoring, energy management, and predictive maintenance. The panel designer must still ensure proper segregation of power and control wiring, EMC-friendly cable routing, and suitable 24 VDC control power architecture. Communication does not replace hardwired safety functions or proper motor protection coordination.
Heat management is one of the main design checks. Soft starters generate losses during ramp-up and, in some configurations, during steady operation. Panel builders calculate total internal heat load from the soft starter, PLCs, power supplies, relays, terminal blocks, and other feeder devices, then select ventilation or cooling accordingly. Common solutions include filtered fans, louvres, roof extractors, heat exchangers, or simply a larger enclosure. The design must keep component temperatures within manufacturer limits and satisfy IEC 61439 temperature-rise verification for the complete assembly.
At minimum, coordinate the soft starter with an upstream MCCB or fuse, motor overload or electronic motor protection relay, and the bypass contactor if used. For larger systems, an ACB may serve as the incomer, with downstream feeder MCCBs providing branch protection. The goal is selectivity and protection of the semiconductor stack against short circuits while allowing normal starting currents. Coordination should follow the soft starter manufacturer’s approved combinations and the requirements of IEC 60947 series devices within the IEC 61439 panel.
In custom engineered panels, soft starter feeders are often arranged in Form 2 or Form 3 segregation, while higher-maintenance or higher-continuity designs may use Form 4 separation. The choice depends on whether the goal is simple segregation of busbars from functional units, isolation of outgoing terminals, or improved maintainability without shutting down adjacent circuits. Under IEC 61439, the form of separation must be clearly defined and matched to the required service continuity, access safety, and wiring space for power and control conductors.
They are widely used in water and wastewater pumps, HVAC fans and chilled water systems, conveyors, crushers, mixers, compressors, and process skids. Any application with high starting current, belt-driven loads, or sensitivity to mechanical shock benefits from soft starting. In a custom engineered panel, the soft starter is often chosen instead of a VFD when speed control is not required but reduced starting stress and simpler operation are desired. This makes it a practical, standards-compliant solution for OEM machinery and industrial utility systems.

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