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Fourth Lesson Im

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CLIL, blocked rotor test induction moto

CLIL, blocked rotor test induction moto

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  • Transcript

    • 1. CLIL experience Content and Language Integrated Learning 4 th Fourth lesson
    • 2.
      • Another test in order to have motor parameters is blocked rotor test . This test is similar to the short circuit test of transformer.
      • Purpose of this test is to determine load dependant losses and stator & rotor reactance and rotor resistance .
      • The rotor is blocked to prevent rotation and balanced voltages are applied to the stator terminals at rated frequency. Applied voltage is gradually increased till rated current is achieved.
      • Current, voltage and power are measured at the motor input and from this data motor parameters are calculated.
      Three-phase induction motor OBJECT: To perform blocked rotor test of 3-phase Induction M.
    • 3. Theory
      • Under blocked rotor condition the rotor is at rest and, therefore,
      • the slip is unity. The load resistance R 1 (1-S)/S is zero.
      • Thus the equivalent circuit of Fig.
      I A
    • 4. Theory In an induction motor, if full voltage is applied across the stator terminals with the rotor not allowed to rotate, about six to eight times its full-load current will flow in the circuit. Blocked-rotor test is conducted at a reduced voltage V S so that current, I S equals to only the full-load current flow through the circuit. The applied voltage V S under blocked rotor condition is, therefore, about one-sixth to one-eighth of the normal voltage. At this reduced voltage the current I 0S flowing through the parallel branch is very small, and can be neglected. R e ’ and X e ’ are stationary resistence and reactance in series connected across the applied voltage, V S . If W S is the input power under blocked-rotor condition, I S is the current and cos φ S is the power factor, then as a result: 
    • 5.
      • R 1 can be measured by ammeter-voltmeter method by applying DC to
      • the stator winding. To get AC resistance at 50Hz, the value of R 1 so
      • obtained is to be multiplied by a factor, say, 1.5. Thus R 1 and R 2 ’ of
      • R e ’ can be separated as R 2 ’ = R e ’- R 1 . There is no simple way of
      • separating X 1 and X 2 ’ from X e ’ except arbitraly. X 1 may be taken
      • equal to X 2 ’ so that X 1 = X 2 ’ = X e ’ / 2 .
      • Thus the equivalent circuit elements as envisaged in Picture are
      • found out. As mentioned earlier, all calculations regarding the
      • performance of an induction motor can be done using the equivalent
      • circuit with some approximations.
      Theory The impedence And
    • 6. Elaborations otherwise
    • 7. Three-phase induction motor CIRCUIT DIAGRAM APPARATUS 1. Voltmeter 2. Ammeter 3. Two wattmeters 4. Two Auto transformer OBJECT: To perform blocked rotor test of 3-phase Induction M.
      • AIMS
      • load dependant losses
      • stator & rotor reactance
      • rotor resistance
    • 8. Procedure
      • Choose the apparatus and measuring instruments.
      • Choose the connection: star or delta
      • Make the circuit as shown in the picture.
      • Keep rotor of induction motor pressed, so that it cannot
      • rotate even upon energization.
      • start increasing voltage slowly till at the 10% plus of the
      • rated current is achieved.
      • Note down the readings of all instruments connected.
      • Repeat the test with decreasing current until zero.
    • 9. Results
    • 10. Results
      • Diagram
      V S [volt] 0 25 50 75 100 125 150 175 200 225 250 275 0 2 4 6 8 10 12 14 16 18 20 22 24 V S [V] V S V R I R I cc
    • 11. Observation - Results
    • 12. Results W S [watt] 0 50 100 150 200 250 300 350 400 450 500 550 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 W S [watt]
    • 13. Results cosf S 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 cosf S
    • 14. Results V S [volt] 0 10 20 30 40 50 60 70 80 90 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 V S [V]
    • 15. Results
      • Diagram result
      V S [volt] 0 25 50 75 100 125 150 175 200 225 250 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 V S [V] V R V S I R I CC
    • 16. Answer to the following questions
      • How will the power factor vary if the voltage supply decreases?
      • To what test is similar the blocked rotor test?
      • What are the aims of the blocked rotor test?
      • What instrument can the motor speed be measured with?
      • How much is the voltage when the current is rated?
      • Under blocked rotor condition, how is the slip?
      • How much is the percentage on the voltage at blocked rotor test V S compared with rated current I R ?
      • Under blocked rotor condition, how is the load resistance R 1 (1-S)/S ?
      • What is the procedure in order to carry out blocked rotor test of 3-phase induction motor?
      • How much the current will flow in the circuit when the rotor is blocked and rated voltage is applied to the stator terminals ?
    • 17. Fill the gaps
      • Blocked rotor ……. is similar to short circuit test
      • of ………..
      • The …….. is blocked to prevent ………….
      • Applied ………. is gradually increased till rated …………. is achieved
      • From data input of current, voltage and ……… motor parameters are …………..
      • Under ……….. rotor condition the slip is ……. and the load resistance R 1 (1-S)/S is ………..
      • The applied ……….. V S under blocked rotor condition is about ………… to one-eight of the normal ………...
      • Under reduced voltage the ………. I 0S flowing through the parallel branch is very small, and can be ………….