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| Subject - HI! I have a question? | |
| tinyspicygirl |
I'm trying to look for a web site that can show me parts of a 3 phase motor and single phase and i can't find it,i have a test on monday and i need this info please help me thank you, good bye
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| Scott Vickrey | Here's a link two a three phase motor. Three phase motor disassembled and labeled Here's a link to a single phase motor. Single phase motor disassembled and labeled Notice how fat the windings are for the single phase motor? This is because on a single phase motor there are actually two sets of windings. The start windings and the run windings. The are controlled by a centrifugal switch. Unfortunately this switch is not shown in the single phase image because you would have to see it from the other direction. |
| tinyspicygirl | Hi Scott and thank you for your response it was really helpful. |
| tinyspicygirl | Do you have any suggestions of a web page about troubleshooting motors? |
| Scott Vickrey | I was unable to find this information. I have started a new topic dedicated to filling this void. Check it out. Troubleshooting Alternating Current Motors and Their Control Circuits |
| avani | can anybuddy answer why the airgap in IM is smaller compered to DCmotor? |
| avani | why the tranformer is rated in KVA? |
| avani | why a 3 phase IM will not start on 2 phase.....while it can run on 2 phase during run operation.....please answer me i have to submit it on monday......good day |
| JimmyDee | quote: All motors need to have a rotating magnetic field if they are to be self starting. I think you meant to say, single phase and not 2 phase but a single field winding by it self does not produce a rotating magnetic field. If you start the motor by some other means, the magnetism that is now produced or induced in the rotor will now induce a magnetic field in the other two windings (or poles) that are not energized. They do not have as strong a magnetic strength as the one that is being energized, so the motor lacks power. This condition is called single phasing and will destroy the motor if there is any load on it at all. Jim |
| JimmyDee | quote: I will assume you mean by IM, an induction motor. I am not 100% sure but will take a try at it. Because an induction motor has no power applied to its rotor, the magnetic field it produces to enable it to rotate, needs to be produced by induction. The strength of the rotors magnetic field will be greatly increased by being closer to the magnetic pole that is inducing the power to create the rotor's magnetic field. A DC motor has power applied to both the rotor and field. So although not as important for efficency and power production, it is still is a very close gap. Jim |
| avani | thanks jimmydee for reply....but still one cofusion......the ouestion is "a 3 phase induction motor is designed for 3 phase.....and is running.....now suddenly one phase goes off then also it keeps running.......at the same way..when it is at steady state......and only 2 phase available....then 3 phase ind.motor....will not start...."why? please reply |
| JimmyDee | quote: I thought I covered that. First of all when you have one of the phases (lets not call them phases let us call them wires) goes off, you will only have one phase available, not two. Adding the third wire allows for 3 phases and only having two wires (what you are calling phases) will only give you single phase. If a wire is dropped off the motor, yes it will run but at higher amperage and less power. The additional power to the 2 other sets of poles it needs to keep it running, is generated from within because the rotor is magnetized and that magnetism is creating everything needed in the 2 sets of stator windings to keep the motor running, although not efficiently. Because the motor is not rotating when we try to start, we loose the generator effect from the rotor and it will not move. With all wires hooked up, we have a rotating magnetic field produced by the sets of stator winding and that is ample magnetic movement to create the needed rotor magnetism to start the motor. Hope this helps. Sorry I can't be there to draw the answer on a chalk board while explaining. Jim |