DEESYS DTR-57 Digital Thermal Relay Product Description

Overview

DEESYS DTR-57 is a digital thermal overload relay (49) from DEESYS, matching the same series family as DFR-021D phase loss relay. This DTR-57 uses external CT for current sampling, providing electronic thermal overload protection for three-phase AC motors, supporting thermal memory, motor temperature PTC input and fault latch function. It is widely used in MCC, pump, fan and compressor control circuits for new construction, retrofit and spare‑part replacement of DEESYS motor protection relays.

Features

DEESYS DTR-57 adopts electronic thermal simulation algorithm, simulating the heating curve of motor winding, with adjustable trip class (5/10/10A/20/30). This relay supports PTC thermistor input for direct winding overtemperature protection. DTR-57 has LCD display for real-time three-phase current, thermal capacity percentage and fault code reading. It supports auto-reset / manual-reset selection, separate overload alarm and trip relay output. Thermal memory function retains accumulated heat value after temporary power failure, avoiding premature restart of hot motor. It works with MCT series current transformer for wide current range coverage, and supports start-lock delay to skip motor starting inrush. Compact DIN rail mounting design fits standard control cabinet layout.

Specs

• Brand: DEESYS

• Model: DTR-57

• Type: Digital thermal overload relay (49 motor thermal protection)

• Control supply: AC/DC 100–240 V, 50/60 Hz

• Sampling: Matched with DEESYS MCT series CT

• Trip class: Adjustable 5, 10, 10A, 20, 30

• Input: PTC motor temperature sensor

• Output: 2 relay contacts (alarm + trip)

• Reset mode: Auto / Manual latch

• Display: LCD, current & thermal load percentage

• Mounting: DIN rail

• Standard: IEC 60947-4-1

Principle

DEESYS DTR-57 receives secondary current signal from MCT CT. The MCU calculates the motor thermal capacity by integrating current over time according to selected trip class. When thermal accumulation exceeds the threshold, the trip relay acts to cut the motor control loop. PTC input directly monitors winding temperature and triggers independent overtemperature protection. Thermal memory keeps heat value during power-off; after cooling down, the relay can reset automatically or manually. Relay status signals are sent to contactor control circuit and PLC alarm system.

Applications

DEESYS DTR-57 is deployed on water pumps, cooling fans, blowers, compressors and general manufacturing AC motors. This digital thermal relay prevents motor burnout caused by continuous overload and blocked rotor. DTR-57 fits motor protection loop overhaul and spare replacement of DEESYS digital thermal relays.

Installation & Maintenance Notes

Follow official DEESYS DTR-57 manual during installation of DTR-57. Handle CT wiring carefully to avoid CT secondary open circuit hazard. Set rated current and trip class matching motor nameplate. Back up parameters before replacement. After replacement, verify PTC wiring, reset mode and thermal memory setting. Confirm exact part number DTR-57; it must use matched MCT CT and cannot be substituted by DFR-021D phase unbalance relay.