Motor protection
Protection relay dedicated to be used in protection systems of motors. It fulfills protection against faults, overloads and current unbalance. The device integrates protection, measuring, control and registry functions.

Manuals, diagrams, technical details


Product description

Protection set

50/51 instantenoues/definite-time, two-stages, three-phase overcurrent protection
50N/51N ground overcurrent, definite-time, two-stages protection (ver. A)
49M thermal overload, inverse-time current protection
51LR overcurrent, against motor stall
51LR overcurrent, against locked rotor
38 temperature-based (PTC-sensors) (ver. B
37 undercurrent, against motor idle
48/66 motor start-up supervision
46 current unbalance protection (negative-sequence overcurrent)
59/27 under-/overvoltage, definite-time, two-stages (ver. C)
62 external protection

Main features

  • 4 measuring inputs
  • measurment of analog input values
  • real time clock
  • event recorder with capacity up to 500 records
  • last disturbance parameters recorder
  • samples or magnitudes of disturbance and logic states recorder
  • Tripped currents counter
  • Two binary inputs for cooperation with external protection purposes, possibility to be used as blocking inputs
  • Trip impulse
  • alphanumeric LCD display (2×16) and six buttons enabling operation of the relay
  • visual indication (by LED diodes) of pick-ups and trips, exceeding of counters or proper operation of relay
  • 7 programmable relay outputs (S1-S7)
  • RS-485 port for communication with PC computer or supervision and control system (MODBUS-RTU protocol)
  • self-test system of proper operation of relay control
  • enclosure construction enables three types of mounting: 35 mm rail, surface mount or flush mount

On the basis of three measured phase currents, the negative-sequence of current is calculated which is the value of current unbalance. Exceeding of any set threshold value causes the reaction of the relay according to the configuration. Communication interface provides measured and calculated electrical values, binary inputs and outputs states and saved records. The manufacturer provides PC software allowing to set the relay, confirm signals, graphical display of measured values and browse records.


Rated measuring current In 1A or 5A
Rated measuring voltage Un 100V
Rated frequency 50Hz
Auxilliary voltage 24V DC, od 48V do 60V DC,
110V DC/AC, 230V DC/AC
Control voltage acc. to aux voltage
Setting ranges of current threshold values
– 50/51 protection functions  (0,2÷30) In
– 50N/51N def.time protection functions  (5÷500)mA or (5 ÷ 5000)mA
– 46 protection function (0,1÷1) In
Base current Ib setting range:
– 51LR (locked rotor) function (0,1÷2,5) In
– 49M, 51LR (motor stall), 48/66 protection functions (0,2÷1,2) In
Setting range of temperature threshold value  ϑ =(40 ÷ 200)°C
Setting range of voltage threshold value (0,05 ÷ 1,20) Un
Setting range of operating time
– definite-time operating characteristics  (0÷99,9)s

– according to 49M protection function characteristic,

defined by EN-60255-8 standard

Relay response time for 50/51 protection functions ≤40ms
Accuracy of current inputs (if I=In) 2,5%
Accuracy of voltage inputs (if U=Un) 1%
Accuracy of time measuring 1% ± 10ms
Burden in measuring inputs ≤0,5VA/input
Burden of supply module ≤5W
Continous measured current 4In
Thermal withstand (1s) 80In
Dynamic withstand 200In
Relay outputs data:
Max. breaking capacity by 250V DC
– resistive load 0,3A
– inductive load of L/R ≤40ms 0,1A
Max. breaking capacity by 250V, 50Hz
– inductive load, cosϕ=0,4 3A
Continuous contact carry 6A
Ambient temperature (253÷328)K/(-20÷55)°C
relative humidity ≤80%
Ingress Protection degree IP40
Weight ~0,7kg
Dimensions (height x width x depth) 75 x 100 x 120 mm
Electromagnetic compatibility acc. to PN-EN 60255-26
Insulation according to PN-EN 60255-5

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