Best 3 Phase Overload Relay Solutions for Industrial Motors
Yes—3 phase overload relays protect three-phase motors by detecting overload current, phase loss, and unbalance. This guide highlights five solid options across solid-state, thermal, and multifunction relays, helping buyers match the right device to motor size, control equipment, and installation constraints. Suitable buyers include panel integrators, maintenance technicians, and plant engineers seeking reliable overload protection with adjustable settings and clear reset options. Below is a quick summary table of the chosen products to compare at a glance.
| Product | Best For | Key Feature |
|---|---|---|
| Siemens 3UB81234EW2 Solid State Overload Relay | Medium-sized 3-phase motors, DIN-rail panels | Adjustable trip classes (5/10/20/30) via DIP-switches |
| JR28-25 5.5-8A Thermal Overload Relay | Directly under contactors, compact DIN-rail systems | Rugged thermal element with phase failure protection |
| Schneider Electric DPER07 Easy TeSys | HVAC, pumps, and compact control panels | Compact modular design; 0-4000 Hz network frequency use |
| Siemens 3UB81334GW2 Solid State Overload Relay | Higher current 3-phase motors, robust protection | Adjustable trip classes and solid-state protection |
| SymCom MotorSaver Plus 3-Phase (777-P2) | Industrial conveyors, HVAC, large motors | Fully programmable electronic overload with external CTs |
Siemens 3UB81234EW2 Solid State Overload Relay
Best for mid-size 3-phase motors used in panel-mounted control schemes. This relay uses solid-state electronics to manage overload without heater elements, reducing maintenance needs. It supports selectable trip classes 5, 10, 20, or 30 via DIP-switches, enabling precise protection aligned to motor FLA. Manual or automatic reset options help with controlled testing and startup sequences. Caution: verify DIP settings match motor full-load current to avoid nuisance trips.
JR28-25 5.5-8A Thermal Overload Relay
Better for tight spaces under standard contactors in 3-phase motor starters. This thermal relay offers an adjustable current setting from 5.5 to 8A, suitable for motors within that range, and includes 1NO/1NC auxiliary contacts for basic control circuits. It features manual or automatic reset and a test/stop interface for commissioning. Best for applications where space and a straightforward thermal mechanism matter; avoid if motor current exceeds the 8A range or if frequent reconfiguration is needed.
Schneider Electric DPER07 Easy TeSys Thermal Relay
Best for HVAC and climate-control equipment where space is at a premium. This relay combines modularity with a compact footprint and supports 0-4000 Hz network compatibility, plus a 600V UL/690V IEC insulation rating. It is designed to protect three-phase motors, compressors, and pumps against overloads, phase failures, and unbalances. Caution: ensure mounting location and wiring fit the module’s dimensions and included terminations.
Siemens 3UB81334GW2 Solid State Overload Relay
Best for higher-current 3-phase motors requiring more robust protection. This unit offers adjustable trip classes (5/10/20/30) via DIP-switches and a solid-state design that eliminates the need for heaters, reducing maintenance and replacement parts. Best for panel builders needing a reliable, configurable protection device in a DIN-rail assembly. Caution: verify that the motor current stays within the relay’s adjustable range to prevent misprotection.
SymCom MotorSaver Plus 3-Phase Power Monitor/Overload Relay
Best for complex or critical systems with variable loads, conveyors, and HVAC equipment. The 777-P2 is a fully programmable electronic overload relay designed for 200-480V 3-phase motors, supporting external CTs for larger current ranges (2-800 A). It provides advanced protection for overload, phase unbalance, and related faults, suitable for users who need flexible protection and integration with existing control wiring. Limitation: external current transformers are required for higher current measurements.
Buying Guide: Key Purchase Considerations
What motor current range do you need to protect? Match the relay’s adjustable range to the motor’s full-load current (FLC) to avoid nuisance trips or underprotection.
What type of protection do you require? Thermal relays react to heat at overload, while solid-state relays provide fast, heater-free protection and can be more compact.
How will the device be mounted? DIN-rail compatibility and panel space influence your choice between compact or modular designs.
Do you need monitoring or remote integration? Some units offer programmable logic, abnormal condition indication, or compatibility with external CTs for larger systems.
Reset behavior and accessibility? Manual versus automatic reset affects startup sequencing and maintenance workflow. Choose according to the preferred control scheme.
Frequently Asked Questions
- What is a 3 phase overload relay? A device that protects three-phase motors from overload, phase loss, and unbalance by triggering a protective trip based on current and/or thermal elements.
- When should I choose a solid-state versus a thermal overload relay? Solid-state relays are compact and maintenance-light, while thermal relays are simple, robust, and widely compatible with older panels.
- How do I select the correct current setting? Set the relay to a current slightly above the motor’s full-load current (FLC) to avoid nuisance trips while protecting the winding.
- Do I need auxiliary contacts? Some models include them for control circuit signaling; consider your PLC or starter wiring needs.
- Can I use these with any 3-phase motor? Compatibility depends on voltage, current range, and mounting compatibility; verify with the motor and contactor assembly.
- What maintenance is required? Regular inspection of wiring, reset mechanisms, and indicators helps ensure continued protection and proper operation.