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Microprocessor Motor Protection Relays of 0,4 kV
in the Networks with Isolated Neutral
RDC-01-053, RDC-01-203

RDC-01-053, RDC-01-203 - microprocessor motor protection relays

Microprocessor relays of the RDC-01-053, RDC-01-203 series (with digital control and indication of controlled parameters) are intended for protection of electric motors of 0,4 kV in the networks with isolated neutral.

The relays RDC-01-053, RDC-01-203 are intended for protection of three-phase asynchronous electric motors, including submersible pumps, 3x127/220 V or 3x220/380 V (phase/linear) from undesirable consequences:

  • overload;
  • asymmetry of loading;
  • underrunning;
  • supply overvoltage;
  • reduction of supply voltage;
  • wrong phase rotation;
  • reduction of insulation resistance of motor coils before start-up and switching of electric circuits at achieving of the one of the controlled parameters of previously programmed level.

At the same time except protective functions the relay has a number of important service functions:

  • possibility of monitoring of the following parameters:
       - consumption current for each phase (IA, IB, IC);
       - network voltages for each phase (UA, UB, UC);
       - network frequency;
       - counter of motor term of life;
       - anomalies in network and the reasons of the taken place critical conditions;
  • the controlled number of automatic start-ups after emergency shutdown (up to five start-ups with time interval between repeated start-ups 15 s);
  • protection of the controlled parameters against unauthorized access (password);
  • possibility of cleaning of the kept parameters about accident without shutdown of the device.

Memory of settings is non-volatile and can keep values during all term of operation.
Settings and parameters are used individually for each electric motor, and it provides its reliable protection and increases operation term.
Service conditions: for modification of U3: –40…+55 °С; for modification of T3: –10…+55 °С.
At current overloading shutdown delay time depends on time of starting of the electric motor and value of current overloading.
Relay outside dimension: 140х70х137 mm.

SUZD - the stations of control of electric motors
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 relays RDC-01-053, RDC-01-203

Characteristics of the devices RDC-01-053 RDC-01-203
Rated current, A 1-500 1-20
Switching-off at the current overloading of the electric motor + +
Switching-off at the electric motor operation with underrunning ("dry course") + +
Switching-off at the electric motor operation with prohibitive current asymmetry + +
Switching-off at excess of the supply voltage +/off +/off
Switching-off at decrease of the supply voltage +/off +/off
Prohibition of the switching-on at wrong phase rotation - -
Prohibition of the switching-on at insulation fault of electric motor - -
Prohibition of the switching-on at sticking effect of starter/contactor (or at the leakage current via starter/contactor) + +
Restriction of the number of repeated start-ups of the electric motor + +
Service functions    
Digital indication of operating modes + +
Counter of motor age limit with step 1 min 1 min
Measurement of effective current values for each phase + +
Measurement of effective voltage values for each phase + +
Indication of frequency of supply power network + +
Cleaning + +
Password + +

Main parameters and technical characteristics

Modifications of RDC-01... 053 203
Rated supply voltage Urated of single-phase current, 50 Hz 220 V
380 V
220 V
380 V
Permissible deviations of supply voltage 30%...+25% Urated 30%...+25% Urated
Rated input current of internal current transformers for each phase 5 А 20 А
Average main error of voltage/current measurement 2,5 % 2 %
Error of frequency measurement 0,1 Hz 0,1 Hz
Number of decimal places of the indicator 4
(1 decimal place - mode, 3 decimal places - value)
Number of LED indicators:/td> 6 6
      - status indicator of output relay + +
      - indicator of overloading + +
      - indicator of voltage decrease + +
      - off-load indicator + +
      - indicator of current asymmetry + +
     - indicator of voltage excess + +
Setting of limits for voltage:
      - Setting of rated supply voltage of motor Urated

220, 380 V

220, 380 V
      - Setting of maximum voltage Umax (110…125)% Urated
      - Setting of minimum voltage Umin (70…95)% Urated
Hysteresis for actuation voltage 5 %
Discretization of settings for voltage 1 V
Setting of limits for current:
      - Setting of transformation ratio of external current transformer КТ


      - Setting of motor rated current Irated 1...500 А 1...20 А
Hysteresis for actuation current 5 %
Setting of actuation limit of current overload: (1,1...2,0) Irated, discretization 0,1
      - actuation limit for underrunning (off-load) (20...85)% Irated
      - setting of asymmetry of the loading current Iasym (20...55)% Irated
Setting of the time parameters:
      - setting of start-up time of electric motor tstart-up

(1...25) sec
      - setting of actuation delay for underrunning (off-load) tdelay (0...255) sec (1...255) sec
      - setting of actuation delay for voltage (Umax, Umin) and for current (Iasym, phase break), tdelay (1...255) sec
      - setting of a number of automatic repeated start-ups after emergency shutdown for current (0...5) in (15±3) sec
Switching capacity in the circuits of alternating current АС-22, VА about 250 VА
Weight of the relay, kg not more than 0,5 kg
Mechanical durability and electrical endurance of the relay, cycles not less 500 000 cycles
Limit of actuation at decrease of insulation resistance of the motor coils 500±100 кОм
Type and a number of the relay contacts 1 make contact
Effective age of the relay not less 8 years
Power consumption in the range of the supply voltages, VА not more than 5 VA

The relay shouldn't have false operations (actuations of the make contact) at short-term voltages dips and surges of voltage during the time not more than 50 ms.

At the request of the customer the RDC-01-053 device can be presented with current transformers of the following ranges:

Range of current transformers, А

Outside and linkage dimensions of the relay RDC-01

Outside and linkage dimensions of the relay RDC-01