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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Shaded pole motor, 2500rpm
Please can anyone help me find one of these? It looks similar to
http://tinyurl.com/3xykj3 but maybe with a deeper stack of stator laminations. Two small complications: * It must be 2500rpm nominal (it's to replace a 1250rpm motor) * The shaft needs to be 0.25in diameter (not 6mm) and about 2in long. These used to be bog-standard items, but they all went to hide when they saw me looking. AIUI there is no way to modify the existing 1250rpm motor, because the speed is determined by the number of 'poles' in the rotor construction. -- Ian White |
#2
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Shaded pole motor, 2500rpm
In message , Ian White
writes Please can anyone help me find one of these? It looks similar to http://tinyurl.com/3xykj3 but maybe with a deeper stack of stator laminations. Two small complications: * It must be 2500rpm nominal (it's to replace a 1250rpm motor) * The shaft needs to be 0.25in diameter (not 6mm) and about 2in long. These used to be bog-standard items, but they all went to hide when they saw me looking. AIUI there is no way to modify the existing 1250rpm motor, because the speed is determined by the number of 'poles' in the rotor construction. Total ******** - more volts - faster rotation the shaded pole is the pair of thick copper wires on the laminations, its there to determine the direction of rotation, it has no effect on the speed as I said, the rotational speed is a function of the applied voltage, you totally misunderstand what is meant by shaded pole I have approaching a thousand, but with 6mm shafts -- geoff |
#3
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Shaded pole motor, 2500rpm
On Tue, 04 Sep 2007 00:10:34 GMT, raden wrote:
Total ******** - more volts - faster rotation the shaded pole is the pair of thick copper wires on the laminations, its there to determine the direction of rotation, it has no effect on the speed Shaded poles motors may be synchronous or non-synchronous, depending on how their rotor is constructed. For the small low-torque models used to drive timers, they're almost universally synchronous. Evenm the non-synchronous ones are pretty insensitive to increased voltage, as they're limited by the magnetic saturation of the core. |
#4
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Shaded pole motor, 2500rpm
In article ,
Ian White wrote: Please can anyone help me find one of these? It looks similar to http://tinyurl.com/3xykj3 but maybe with a deeper stack of stator laminations. * It must be 2500rpm nominal (it's to replace a 1250rpm motor) * The shaft needs to be 0.25in diameter (not 6mm) and about 2in long. 2-pole shaded pole motors are readily available, but only with a 6mm shaft these days. To get a 0.25" shaft might mean looking in old electrical equipment. AIUI there is no way to modify the existing 1250rpm motor, because the speed is determined by the number of 'poles' in the rotor construction. Many (many) years ago there was a way of getting a 2:1 speed switch with 4-pole motors which had a coil on every pole. For 1500 rpm (off load) the coils were energised in a N-S-N-S 4-pole configuration and for 3000 rpm (off load) the coils were switched to a N+N-S+S configuration, to get an effective 2-pole motor. Any chance with your present motor? Notice the 'off load' distinction. These shaded pole motors do run with a large slip on load, and your '1250 rpm' 4-pole motor is really a theoretical 1500 rpm sync speed motor running at 17% slip. -- Tony Williams. |
#5
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Shaded pole motor, 2500rpm
On 4 Sep, 09:55, Tony Williams wrote:
2-pole shaded pole motors are readily available, but only with a 6mm shaft these days. To get a 0.25" shaft might mean looking in old electrical equipment. Router collet shim from a cheap router 8-) Along with grinding the 6mm cutters into trammel points or doorstops, it also helps to reduce the risk of ever using one of these dangerous 6mm cutters in your 1.4" collet. |
#6
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Shaded pole motor, 2500rpm
Hi,
If you can only get 6mm then a couple of layers of ali from a coke can might shim it out OK. cheers, Pete. |
#7
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Shaded pole motor, 2500rpm
In message , Andy Dingley
writes On Tue, 04 Sep 2007 00:10:34 GMT, raden wrote: Total ******** - more volts - faster rotation the shaded pole is the pair of thick copper wires on the laminations, its there to determine the direction of rotation, it has no effect on the speed Shaded poles motors may be synchronous or non-synchronous, depending on how their rotor is constructed. For the small low-torque models used to drive timers, they're almost universally synchronous. You have looked at the photo he linked to, I presume Evenm the non-synchronous ones are pretty insensitive to increased voltage, as they're limited by the magnetic saturation of the core. I should have said "within a range" up to where they approach saturation .... Of the boiler fans which run at two speeds (purge and full), most are voltage controlled - its cheaper than having a second winding -- geoff |
#8
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Shaded pole motor, 2500rpm
On Mon, 3 Sep 2007 15:32:20 +0100, Ian White
wrote: Please can anyone help me find one of these? It looks similar to http://tinyurl.com/3xykj3 but maybe with a deeper stack of stator laminations. I've got a box full of unused 30 year old ones made by ECM Motors of Schaumburgh with 0.25" shafts, however, all have reduction gearboxes giving 200RPM at the end. Perhaps you could transpose the rotor from yours and build one out of the bits you have plus one of them? What are the dimensions of the one you have? -- Peter Parry. http://www.wpp.ltd.uk/ |
#9
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Shaded pole motor, 2500rpm
In message , Peter Parry
writes On Mon, 3 Sep 2007 15:32:20 +0100, Ian White wrote: Please can anyone help me find one of these? It looks similar to http://tinyurl.com/3xykj3 but maybe with a deeper stack of stator laminations. I've got a box full of unused 30 year old ones made by ECM Motors of Schaumburgh with 0.25" shafts, however, all have reduction gearboxes giving 200RPM at the end. Perhaps you could transpose the rotor from yours Or drift the shaft out and replace it with a bit of silver steel -- geoff |
#10
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Shaded pole motor, 2500rpm
raden wrote:
In message , Andy Dingley writes On Tue, 04 Sep 2007 00:10:34 GMT, raden wrote: Total ******** - more volts - faster rotation the shaded pole is the pair of thick copper wires on the laminations, its there to determine the direction of rotation, it has no effect on the speed Shaded poles motors may be synchronous or non-synchronous, depending on how their rotor is constructed. For the small low-torque models used to drive timers, they're almost universally synchronous. You have looked at the photo he linked to, I presume Evenm the non-synchronous ones are pretty insensitive to increased voltage, as they're limited by the magnetic saturation of the core. I should have said "within a range" up to where they approach saturation ... Of the boiler fans which run at two speeds (purge and full), most are voltage controlled - its cheaper than having a second winding Thanks for all the comments. The source of my confusion about numbers of poles was that I have two shaded pole motors, one that runs at about 2500rpm (about 80% of synchronous speed) while the other motor runs at about half the speed. On closer examination it seems that the rotor and stator construction is actually the same in both motors, and the slower speed is due to one of the stators operating at lower magnetic flux. The rotors and stator/winding parts of the 'fast' and 'slow' motors are mechanically interchangeable, so I tested all four combinations at 230V. One stator/winding could make both rotors run at about 2500rpm, while the other made them both run at about half that speed. All four combinations could be slowed down by reducing the voltage, so it looks like the general case is more magnetic flux = faster rotation. Or to put it another way, more magnetic flux = less slippage under load, and a closer approach to synchronous speed. Thanks also for the suggestions about shimming up a 6mm shaft to 0.25in. One layer of PVC tape worked surprisingly well, as the balance at 2500rpm was not as critical as I'd expected. However, the project then hit another snag, as the faster motor is clearly not designed for continuous operation and gets uncomfortably hot after about half an hour. I will grateful to take up Peter Parry's offer, and try to find a better motor (will contact you by e-mail tomorrow with dimensions). -- Ian White |
#11
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Shaded pole motor, 2500rpm
In message , Ian White
writes raden wrote: In message , Andy Dingley writes On Tue, 04 Sep 2007 00:10:34 GMT, raden wrote: Total ******** - more volts - faster rotation the shaded pole is the pair of thick copper wires on the laminations, its there to determine the direction of rotation, it has no effect on the speed Shaded poles motors may be synchronous or non-synchronous, depending on how their rotor is constructed. For the small low-torque models used to drive timers, they're almost universally synchronous. You have looked at the photo he linked to, I presume Evenm the non-synchronous ones are pretty insensitive to increased voltage, as they're limited by the magnetic saturation of the core. I should have said "within a range" up to where they approach saturation ... Of the boiler fans which run at two speeds (purge and full), most are voltage controlled - its cheaper than having a second winding Thanks for all the comments. The source of my confusion about numbers of poles was that I have two shaded pole motors, one that runs at about 2500rpm (about 80% of synchronous speed) while the other motor runs at about half the speed. On closer examination it seems that the rotor and stator construction is actually the same in both motors, and the slower speed is due to one of the stators operating at lower magnetic flux. The rotors and stator/winding parts of the 'fast' and 'slow' motors are mechanically interchangeable, so I tested all four combinations at 230V. One stator/winding could make both rotors run at about 2500rpm, while the other made them both run at about half that speed. All four combinations could be slowed down by reducing the voltage, so it looks like the general case is more magnetic flux = faster rotation. Or to put it another way, more magnetic flux = less slippage under load, and a closer approach to synchronous speed. Thanks also for the suggestions about shimming up a 6mm shaft to 0.25in. One layer of PVC tape worked surprisingly well, as the balance at 2500rpm was not as critical as I'd expected. However, the project then hit another snag, as the faster motor is clearly not designed for continuous operation and gets uncomfortably hot after about half an hour. I will grateful to take up Peter Parry's offer, and try to find a better motor (will contact you by e-mail tomorrow with dimensions). You can buy cooling rotors at some rip off price (several pounds) from your local HRPC or Partcenter. They are 6mm but you could quite easily drill one out to 1/4 inch. You just need to push the shaft through far enough to accept it If you're near Watford, I could prolly do it for you (we're just down the road from Peter) -- geoff |
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