Experiment 8 Series DC Motor (II)

Transcription

1 Ojectives To control the speed of loded series dc motor y chnging rmture voltge. To control the speed of loded series dc motor y dding resistnce in prllel with the rmture circuit. To control the speed of loded series dc motor y dding resistnce in prllel with the field circuit. Introduction During the previous experiment, it ws mentioned tht there is two wys of controlling the speed of series dc motor. One of them is to chnge the terminl voltge. The other one is to insert resistnce in series with rmture circuit. Both methods will e pplied during this experiment with little edition to the second method. Insted of dding the resistnce in series with rmture circuit, it will e once dded in prllel with rmture circuit nd once in prllel with field circuit. You re expected to e le to understnd the reson of the chnge y the end of the experiment. Altering the Terminl Voltge Procedure CAUTION: AT NO TIME ALLOW THE LOAD TO GO TO ZERO ON A SERIES MOTOR! Using the l equipments shown in Figure 8. (where the nmeplte of the series motor is shown in Figure 8.2), do the proper wiring for the following prts.. Connect the circuit shown in Figure Connect the electromgnetic rek to the dc power supply, nd turn it on until the rek current reches.5 A (this is the point t which the lod torque is out 2 N.m, which is needed to mke sure tht the motor will not turn t high speeds tht will destroy it).. Set the inserted rmture resistor to its mximum vlue. 4. Turn on the dc power supply connected to the motor nd increse its voltge till it reches 22 V. 5. Slowly turn off the inserted rmture resistnce. 6. Increse the lod till you reches full lod (lod t which I m is 7.A) nd mke sure it stys t tht vlue. 7. Complete Tle : Electricl Mchines for Mechtronics Lortory 8

2 Figure 8.: Rel photo of equipments used. 4544: Electricl Mchines for Mechtronics Lortory 8 2

3 Figure 8.2: Series motor tg. -4V-5A -4V-5A 22V-8A -24V-8A 22V-A -24V-A -225V-A % KY DL M2 L L2 L N L L2 L L L2 L L+ L- L+ L- Figure 8.: Wiring digrm needed to control the speed using lternting terminl voltge. 4544: Electricl Mchines for Mechtronics Lortory 8

4 V t [V] I m [A] P in [w] n [rpm] τ [N.m] P out [W] η Tle 8.: Speed control y ltering the terminl voltge Inserting Resistor in Prllel with the Armture Circuit In this method the torque ws decresed, ecuse dividing the mster (line) current etween the rmture circuit nd the prllel resistor, cuses the rmture current to drop ut τ = ki A I (8.) f In this method, I f equls the line current ( I m ), ut I A is less thn it, which mens tht to rech sme old vlue of the induced torque, higher line current will e needed. But wht if we re deling with the rted current? Then it is no longer possile to rech the rted lod reched using the previous speed control method. Procedures CAUTION: AT NO TIME ALLOW THE LOAD TO GO TO ZERO ON A SERIES MOTOR! Using the l equipments shown in Figure 8. (where the nmeplte of the series motor is shown in Figure 8.2), do the proper wiring for the following prts.. Connect the circuit shown in Figure Connect the electromgnetic rek to the dc power supply, nd turn it on until the rek current reches.5 A (this is the point t which the lod torque is out 2 N.m, which is needed to mke sure tht the motor will not turn t high speeds tht will destroy it).. Set the inserted rmture resistor to its mximum vlue. 4. Set the prllel resistnce to its mximum vlue. 5. Turn on the dc power supply connected to the motor nd increse its voltge till it reches 22 V. 6. Slowly turn off the inserted rmture resistnce. 7. Decrese the lod to N.m. 8. Decrese the prllel resistor vlue to decrese the speed with steps of rpm till motor reches its rted current. 9. Complete Tle : Electricl Mchines for Mechtronics Lortory 8 4

5 -4V-5A -4V-5A 22V-8A -24V-8A 22V-A -24V-A -225V-A % KY DL M2 L L2 L N L L2 L L L2 L L+ L- L+ L- Figure 8.4: Wiring digrm needed to control the speed using prllel resistnce with rmture circuit. 4544: Electricl Mchines for Mechtronics Lortory 8 5

6 I = I m - I L I L [A] I m [A] I [A] Pin[W] n[rpm] τ[n.m] Pout[W] η Tle 8.2: Speed control y inserting resistor in prllel with the rmture. Inserting Resistor in Prllel with the Field Circuit In this method the torque ws decresed, ecuse dividing the mster (line) current etween the field circuit nd the prllel resistor, cuses the field current to drop ut τ = ki I A (eqution 8.). In this method, I A equls the line current ( I m ), ut I f is less thn it, which mens tht to rech sme old vlue of the induced torque, higher line current will e needed. But wht if we re deling with the rted current? Then it is no longer possile to rech the rted lod reched using the previous speed control method. But you should note tht using this method, higher torques ws used ecuse if less torques is pplied, the speed of the motor will increse dngerously. Procedures CAUTION: AT NO TIME ALLOW THE LOAD TO GO TO ZERO ON A SERIES MOTOR! Using the l equipments shown in Figure 8. (where the nmeplte of the series motor is shown in Figure 8.2), do the proper wiring for the following prts.. Connect the circuit shown in Figure Connect the electromgnetic rek to the dc power supply, nd turn it on until the rek current reches.5 A (this is the point t which the lod torque is out 2 N.m, which is needed to mke sure tht the motor will not turn t high speeds tht will destroy it).. Set the inserted rmture resistor to its mximum vlue. 4. Set the prllel resistnce to its mximum vlue. 5. Turn on the dc power supply connected to the motor nd increse its voltge till it reches 22 V. 6. Slowly turn off the inserted rmture resistnce. 7. Increse the lod to N.m. 8. Decrese the prllel resistor vlue to decrese the speed with steps of rpm till motor reches its rted current. 9. Complete Tle 8.. f 4544: Electricl Mchines for Mechtronics Lortory 8 6

7 -4V-5A -4V-5A 22V-8A -24V-8A 22V-A -24V-A -225V-A % KY DL M2 L L2 L N L L2 L L L2 L L+ L- L+ L- Resistive Lod Figure 8.5: Wiring digrm needed to control the speed using prllel resistnce with field circuit. 4544: Electricl Mchines for Mechtronics Lortory 8 7

8 I f = I m - I L I L [A] I m [A] I f [A] Pin [W] n [rpm] τ [N.m] Pout [W] η Tle 8.: Speed control y inserting prllel with the field coil 4544: Electricl Mchines for Mechtronics Lortory 8 8