Phone: +38 (044) 406-61-52 (-53, 54), +38 (063) 313-57-17 - Email:

Microprocessor Relay of Protection for Electric Motor 0,4 кV
RDC-01-057-1, RDC-01-057-2, RDC-01-057-3

RDC-01-057-2 - microprocessor relay of protection for electric motor 0,4 кV

The protection relays of motor RDC-01-057-1, RDC-01-057-2, RDC-01-057-3 (with digital control and indication of controlled parameters) are intended for protection of three-phase asynchronous electric motors with voltage of 0,4 kV.

These relays protect from the following situations:

  • Current overload;
  • Loading asymmetry (phases А and С or phases А, В and С);
  • Underrunning (phases А and С or phases А, В and С);
  • Rotor blocking;
  • Single-phase ground short circuit (GSC) for zero sequence current (3 Io);
  • Overvoltage of motor;
  • Reduction of motor supply voltage;
  • Wrong phase rotation;
  • Sticking effect of motor starter.

There are following modifications of the relay:

Modifications Operational power supply of the relay Checking of line supply voltage of the motor Current checking of motor
RDC-01-057-1 Single-phase, AC/DC
100, 110, 220V, 50Hz
no a) for phases А and С, checking of (3I0) at connection of external transformer of zero sequence current;
b) for phases А, С
c) for phases А, В, С
RDC-01-057-2 no 3x110 V, 50 Hz
3x380 V, 50 Hz
RDC-01-057-3 Single-phase, AC/DC
100, 110, 220В, 50Hz

The relay has an opportunity to turn off the action of the following functions:

  • Current cutoff;
  • Protection against maximum voltage (except RDC-01-057-1);
  • Protection against minimum voltage (except RDC-01-057-1);
  • Protection for no-load, dry course;
  • Protection for rotor blocking;
  • Protection for current asymmetry;
  • Protection against ground short circuit;
  • Protection against wrong phase rotation (except RDC-01-057-1).

The relays can work in one of three modes:

  1. Current checking in the phases А and С and 3I0;
  2. Current checking in the phases А,В,С;
  3. Current checking in the phases А and С.

At the same time (except protective functions) the relays have a possibility of monitoring:
     - consumption current for phase (IA, IC), 3I0 или (IA, IB, IC)*;
     - network frequency;
     - motor term of life;
     - line voltage in the network (UAB, UBC, UCA) (modifications with voltage checking).

The relays are manufactured:
     - in climatic modifications for deliveries to areas with a temperate and frigid climate;
     - in climatic modifications for deliveries (export) to areas with tropical climate.

SUZD - the stations of control of electric motors

At the enterprise on the basis of the protection devices of the RDC series the stations of control of electric motors are produced. These stations are intended for work with the three-phase asynchronous motors 550 W – 350 kW of various producers. The stations are made according to various schemes with a possibility of a full complete set of electric equipment and are intended for automatic and manual control, automation, scheduling and also in various systems of water supply where asynchronous motors are used. The stations automatically support the set pressure in the system of water supply or the set level in the tank, provide complex protection of the electric motor against emergency operation. Learn More...

Main technical characteristics of the relay of the RDC-01-057 series

Measuring current circuits of the relay can directly be connected in network with rated current up to 5 A (for networks of 380 V) or via external measuring transformers of current with transformation coefficient in the range (5/5 … 1000/5) and the recommended class of accuracy 0,5. The design of the relay provides the installation by means of projection mounting with front connection connection of wires.

Power supply
Rated (single-phase) operational supply voltage of the relay (direct, alternating), Urated op.
(except RDC-01-057-2)
AC/DC 100, 110, 220 V
Rated frequency 50 Hz
Power consumption, not more than 5 VA
Rated input signals
Rated input alternating current of phases: А and С or А, В, С*, Irated 5 A
Rated current Irated, 3I0 1 A
Rated input (line, three-phase) voltage of the controlled network, Urated 100 V, 300 V
Average main error of voltage measurement 2,5 %
Average main error of motor current measurement ±2,5 % / 5 %
Protection settings for voltage
Setting of rated input line three-phase voltage (Urated), alternating current with frequency 50 Hz 100 V, 380*V, 6 кV, 10 кV
Setting of maximum voltage (Umax)     OFF / (110...125) % Urated
Setting of minimum voltage (Umin)     OFF / (70...95) % Urated
Protection settings for current
Transformer ratio of external current transformer of the phases, Кtf (1...200)
Setting of rated current of the motor Irated (1...990) A
Transformer ratio of external current transformer 3I0, KT, 3I0 (1...100)
Limit of actuation of elements of off-load     OFF / (20...85) % Irated
Loading current asymmetry Iasym     OFF / (20...55) % Ioperated
Rotor blocking for current     OFF / (1,1...6,0) Irated
Current setting GSC (primary values), А     OFF / (0,1...1) Kт 3Io*
(0,02...1) Kт 3Io**
Hysteresis for actuation current 5%
Setting of level of current cutoff, ICC (6...10) Irated
Settings of time parameters
Start-up time of electric motor tstart (1...25) s
Actuation delay of elements of off-load toff-load delay (0,1...30) min
Actuation delay of current element (Iasym, phase disconnection), tАС (1...255) с
Delay at short-circuit to earth tearth (0,1...99,9) s
Delay at rotor blocking tRB (0,1...99,9) s
Actuation delay of voltage element (UMAX, UMIN) (1...999) s
The number of automatic repeated start-ups after current emergency turning off (0...5)
The delays of automatic repeated start-ups (ARS) after current emergency turning off, tARS (0...5)
Output intermediate relays
Intermediate protection relay for the current 1 change-over contact
Intermediate protection relay for the voltage 1 change-over contact
Outside and linkage dimensions of the relay, HхWхD 85 х 140 х 137 mm

Features of operation of output relays

The relays RDC-01-057-1, RDC-01-057-2 and RDC-01-057-3 provide protection and control of the electric motor via the starter, the contactor switch or other devices which are adapted for automatic work and have the disconnecting ability for control of the starter of the high-voltage motor of the protected circuit. Output circuit of the relay are the change-over contact of the executive relay "KI", which is connected consistently with the coil of the starter (contactor) and also the change-over contact of the second executive relay "KU" which can be connected consistently with contacts of the executive relay "KI" for work on shutdown or it is used for a signal at the excess or the decrease of the controlled voltage.

Purpose of output relays

KI - output relay - it actuates for overload current, dry course, current asymmetry.
KU - output relay - it actuates for controlled voltage (excess, decrease).

In case of excess of emergency settings on current the delay timer on shutdown and the blinking indication (red color) of the corresponding light-emitting diode are turned on. If for the determined time controlled parameters (taking into account a hysteresis) don't come back to admissible limits, then the output relay KI actuates (the command for shutdown of the high-voltage switch is given) and the constant luminescence of the corresponding LED indicator takes place.

Purpose of indication elements

LED display RDC-01-057-1 RDC-01-057-2
KI Status indicator of output relay of current protection
KU Status indicator of output relay of voltage protection  
I > Indicator of current overloading
I ≠ Indicator of current asymmetry
I < Off-load indicator / indicator of relay readiness
3I0 Ground short-circuit indicator
U > Indicator of voltage excess  
U < Indicator of voltage decrease  
ABC Indicator of wrong phase rotation of voltage