DEESYS DFR-021D Phase Failure Relay Product Description

Overview

DEESYS DFR-021D is a 3-phase current-type phase failure & unbalance relay (47I) from DEESYS, designed to detect open-phase and three-phase current unbalance for motors and three-phase loads. This DFR-021D works with dedicated current transformer MCT-A31 for current sampling, widely used in motor control centers, pump/fan control cabinets and compressor protection circuits for new construction, retrofit and spare‑part replacement of DEESYS phase protection relays.

Features

DEESYS DFR-021D adopts current-sensing detection principle, can identify open phase and abnormal current unbalance even when the mains voltage is normal. This relay supports adjustable reference current, unbalance threshold, start-lock delay and alarm delay. DFR-021D has LCD display for real-time three-phase average current and unbalance percentage reading. It supports auto-reset / manual-reset selection and pulse / latch alarm output mode. The start-lock timer avoids false alarm during motor startup inrush period. It uses isolated CT sampling and provides relay contact output to trip contactor or send alarm signal to PLC/HMI. Compact DIN rail mounting housing fits standard control cabinet layout.

Specs

• Brand: DEESYS

• Model: DFR-021D

• Type: Phase failure / current unbalance relay (47I)

• Control power: AC/DC 100–240 V, 50/60 Hz, <3 VA

• Primary monitoring current range: 1–160 A (matched with MCT-A31)

• Reference current setting: 1.0–10.0 A, step 0.1 A

• Unbalance setting: 10–90%, step 1%

• Start-lock time: 1.0–60.0 s, step 0.5 s

• Alarm delay time: 1.0–60.0 s, step 0.5 s

• Output mode: Pulse (0.1–10 s adjustable) / Latch

• Reset mode: Auto / Manual

• Accuracy: ±10%

• Mounting: DIN rail

• Required accessory: MCT-A31 current converter

Principle

DEESYS DFR-021D receives secondary current signals from MCT-A31. The internal MCU calculates three-phase current magnitude and unbalance ratio. If any phase is lost or unbalance percentage exceeds set threshold after the start-lock period, the relay triggers alarm contact action. The start-lock timer masks the startup transient to prevent misoperation. After fault disappears, the relay can automatically reset or stay latched until manual reset.

Applications

DEESYS DFR-021D is deployed on large AC motors, water pumps, fans, blowers, compressors and material handling drives. This current-type phase relay protects equipment from overheating and burnout caused by single-phase operation. DFR-021D fits motor protection loop overhaul and spare replacement of DEESYS phase failure relays.

Installation & Maintenance Notes

Follow official DEESYS DFR-021D manual during installation of DFR-021D. Correctly wire MCT-A31 CT secondary; avoid CT open circuit hazard. Set reference current matching motor FLA and set unbalance ratio reasonably. Back up parameter settings before replacement. After replacement, verify start-lock time and alarm output mode. Confirm exact part number DFR-021D; this model must use MCT-A31, cannot work with other CT types directly.