ABB REM 610 Technical Reference Manual

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ABB REM 610 Technical Reference Manual Manual pdf 125 page image

1MRS 752263-MUM Motor protection RelayTechnical Reference ManualREM 610125If the start value of stage I>> is set to be doubled during motor start up (SGF3/8=1),the start value should be set below the start-up current of the motor, i.e to 75...90%x the start-up current of the motor: I>> = 0.75 x 6.2 ≈ 4.65.5.2.2. Protecting a motor at an ambient temperature other than 40∞CData of the squirrel cage motor stated by the manufacturer:Rated power, Pnm 4500 kWRated voltage, Unm 3300 VRated current, Inm 930 AStart-up current of the motor 6.2 x FLCStart-up time of the motor 11 sSafe stall time 19 sAmbient temperature 20...70∞CCT current ratio 1000/5 A (relay input = 5 A)Setting calculationsThe protected unit scaling factor is calculated as follows:1000A930A---------------- 5A5A-------× 1.075 1.08≈=For a direct-on-line started motor, p = 50%.At an ambient temperature of 40∞C the internal FLC is 1.0 x FLC of the motor. Thus,the start-up current of the motor is 6.2 x the internal FLC. A safe stall time of 30seconds is selected as in the previous application example.If the ambient temperature is lower than 40∞C, the motor can be run at a slightoverload in relation to the specified maximum load at 40∞C. If the ambienttemperature is higher than 40∞C, the continuous load must be lower than thespecified maximum load at 40∞C.At an ambient temperature of 20∞C the internal FLC is 1.09 x FLC of the motor.Thus, the start-up current of the motor is 6.2/1.09 = 5.69 x the internal FLC. If a safestall time setting of 30 seconds is selected, the relay will allow two hot starts insteadof one. If this is unacceptable, however, and only one hot start is to be allowed, asafe stall time setting of 23 seconds is to be selected instead.At an ambient temperature of 65∞C the internal FLC is 0.75 x the FLC of the motor.Thus, the start-up current of the motor is 6.2/0.75 = 8.27 x the internal FLC. If a safestall time setting of 30 seconds and a prior load of 0.75 x the FLC of the motor areselected, the relay will not allow a hot start until the motor has been at standstill forseveral minutes. However, if a hot start is to be allowed, a safe stall time setting ofapproximately 50 seconds is to be selected instead.All other settings are as in the previous application example.