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Operating Instructions
Thermistor Motor Protection Relay
7UG0881-1BU20
7UG0
IEC 60947-5-1
IEC 60947-8 A
Please read and understand these instructions before installing,
operating, or maintaining the equipment.
DANGER
Hazardous voltage can cause death or serious injury.
Disconnect power before working on equipment.
CAUTION
Reliable functioning of the equipment is only ensured
with certied components.
Overvoltage category II
(Refer IEC 60947-1)
NOTICE
This product has been designed for environment A. Use of this product
in environment B may cause unwanted electromagnetic disturbances in
which case the user may require to take adequate mitigation measures.
Technical Data
Designation 7UG0881-1BU20
Type Thermistor Motor Protection Relay
Control Supply (Uc) 110 - 240V AC/DC
Tolerance on Control supply 0.85x Uc… 1.1x Uc
Frequency 50/60Hz
Operating temperature 0 to 50°C , 95%RH (non-condensing)
Sensor operating mode
(all values in ohms)
Sensor Short : ≤ 40
Sensor Healthy : ≥ 44 (±3) to < 3.8K (±150)
Sensor Trip : ≥ 3.8K (±150) to < 5.5K (±150)
Sensor Open : ≥ 5.5K (±150) & Above
Sensor Recovery/ Cut-in / Reset : ≤ 1.5K (±60)
Trip Time Instantaneous
Initialization time 3 sec
Relay modes Failsafe and Non-Failsafe mode (Selectable)
Device Operating mode Auto / Manual (Selectable)
Rated output relay current 5A (AC12)
Power consumption (@ 230V) 3 VA
Terminal connections
Thermistor motor protection relay is used to monitor the winding temperature of motors / generators using PTC sensors and to protect them from
abnormal overheating in accordance to the product standard IEC 60947-8, control units for built-in thermal protection (PTC) for rotating electrical
machines.
PTC resistor sensors which are built-in into the motor windings, measures the motor heating. With increase of the temperature in the motor, the
resistance of the PTC sensors will increase.
Operating modes :
1. Sensor Short : Sensor is short / damaged.
2. Sensor Healthy : The motor is running safely.
3. Sensor Trip : When the motor exceeds its temperature beyond its safety limit, it is in trip condition. It stays in trip condition until the motor cools
down and reaches Cut-in.
4. Sensor Open : Sensor is open / break.
5. Sensor Recovery / Cut-in / Reset : After the motor cools down, it reaches Cut-in condition. The relay switches automatically, in Auto mode.
Whereas in Manual mode, the user has to manually reset (PRG Key or Remote reset R1-S1) when in Cut-in condition.
7UG0881 - 1BU20
0.5 Nm
Solid
1 x (0.75 to 2.5) mm2
2 x 0.5 to 2 x 1.5 mm2
Stranded with end sleeve
1 x (0.5 to 2.5) mm2
2 x (0.5 to 1.5) mm2
Note: 1. Compatible with both single and triple PTCs.
2. At ambient, when PTC sensors connected in series, total resistance value
should not exceed more than 1.5kΩ i.e. (R1+R2+R3+...+Rn)Amb ≤ 1.5kΩ.
