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#1
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Horsepower of electric motor V/S Size of motor
I have a 1/2HP electric motor on a power saw, and that motor is fairly
large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... Thanks |
#2
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Horsepower of electric motor V/S Size of motor
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#3
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Horsepower of electric motor V/S Size of motor
wrote in message
... I have a 1/2HP electric motor on a power saw, and that motor is fairly large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... From: http://machinedesign.com/article/gre...nt-motors-0619 Six factors account for most of the energy lost in an ordinary induction motor: iron-core losses, stator resistance, rotor resistance, windage and friction, and stray load losses. NEMA Premium motors minimize these factors in a variety of ways, usually through use of high-grade steel and increased use of active materials. For example, high-grade steel in the rotor lets manufacturers use thicker laminations that take less time to manufacture, but which still reduce ironcore losses caused by circulating currents. Similarly, manufacturers reduce stator resistance by boosting the amount of copper in the stator windings. -- Bobby G. |
#4
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Horsepower of electric motor V/S Size of motor
On Nov 30, 5:03*am, wrote:
I have a 1/2HP electric motor on a power saw, and that motor is fairly large. *I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. *That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? *Is there another factor to take into account besides the HP? *Is it torque, or some other factor? *Somehow I cant see how this small pump motor could power my saw.... Thanks The technology of motor has has improved vastly over the years. Better, more heat resistant/thinner insulation, better magnetic matrials, better design, Smaller clearance between stator and rotor. Result, smaller and cheaper motor. HP equivalent to Watts. HP =speed of motor X torque x a conversion factor Or more exactly:- 2 x pi x N x T divided by 33.000 2 x pi converts to radians N is speed in rpm Tis the torque in pounds feet. As far as I remember in your antique system. An electric motor size is limited only by heat losses and ability to disperse them. |
#5
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Horsepower of electric motor V/S Size of motor
one thing for certain newer motors, ones produced in the last 10 years
are physically smaller..... they are welded or glued together, lack heavy steel cases, and no doubt cant last as long as older ones, no service needed, typical cheap modern design. toss and replace when it has a problem... |
#6
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Horsepower of electric motor V/S Size of motor
On 11/30/2011 3:46 AM, harry wrote:
On Nov 30, 5:03 am, wrote: I have a 1/2HP electric motor on a power saw, and that motor is fairly large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... Thanks The technology of motor has has improved vastly over the years. Better, more heat resistant/thinner insulation, better magnetic matrials, better design, Smaller clearance between stator and rotor. Result, smaller and cheaper motor. Adding to that, motor design was pushed closer to the electrical design edge to make cheaper motors. (Some of that has been reversed in high efficiency motors.) Many years ago the standard 'frame size' was reduced a couple times if I remember right. If the saw has a motor that is quite old it may be larger than an equivalent motor made now. Some motors have a "service factor" rating (maybe 1.15). That means the motor can be operated beyond its rated HP with a somewhat shorter life but not drastically shorter life. I never looked, but motors with a SF rating may be larger. Motors have a nameplate "duty" rating, usually "continuous". Sjouke suggests the pump may have an intermittent rating. Then there is the deliberate misrating of motors, as was done for instance by compressor manufacturers. HP equivalent to Watts. HP =speed of motor X torque x a conversion factor In case that isn't clear, lower RPM motors are likely larger for the same HP. ... An electric motor size is limited only by heat losses and ability to disperse them. There are limits, like saturating the magnetic material. -- bud-- |
#7
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Horsepower of electric motor V/S Size of motor
On Nov 30, 12:59*am, Sjouke Burry s@b wrote:
wrote : I have a 1/2HP electric motor on a power saw, and that motor is fairly large. *I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. *That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? *Is there another factor to take into account besides the HP? *Is it torque, or some other factor? *Somehow I cant see how this small pump motor could power my saw.... Thanks 1. Skimpy design. 2. The waterpump may be cooled a bit by the pumped water. 3. The designer might have counted on short runs with * *enough cooling down in between. All that allowes a smaller motor. I think that the water cooling may be a big part of it. Heat buildup is part of the reason regular continuous-duty electrical motors are so large - for example, an automotive starter motor develops more power than likely anything in your workshop but is relatively small - because it's not designed for continuous usage, so heat buildup is pretty much neglected as a design consideration. But try to use one under load for more than a couple minutes at a time, and see what happens... nate |
#8
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Horsepower of electric motor V/S Size of motor
Ever notice the HP ratings on shop vacuums?
I saw one that said 6 HP yet it had a 16 gauge power cord on it. Since 1 HP = 746 watts, that cord was passing 4476 watts or 37.3 amps. WTF? How could that be? It seems as though someone is stretching the HP rating a bit. Didn't the small gas engine companies get busted for lying about their HP? |
#9
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Horsepower of electric motor V/S Size of motor
In article ,
wrote: I have a 1/2HP electric motor on a power saw, and that motor is fairly large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... Thanks Without even going into considerations of efficiency, torque characteristics, or type of moter (induction, series/universal, etc.) one common way is simply to increase the operating RPM. A 1 HP motor operating at 3600 rpm can be significantly smaller than one operating at 1800 rpm. -- There are no stupid questions, but there are lots of stupid answers. Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org |
#10
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Horsepower of electric motor V/S Size of motor
Moe Gasser wrote:
Didn't the small gas engine companies get busted for lying about their HP? I've got a form to add data to for that sitting on my desk. |
#11
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Horsepower of electric motor V/S Size of motor
On Nov 30, 5:33*pm, Moe Gasser moe.gas...@flatulators-
anonymous.pffft wrote: Ever notice the HP ratings on shop vacuums? I saw one that said 6 HP yet it had a 16 gauge power cord on it. Since 1 HP = 746 watts, that cord was passing 4476 watts or 37.3 amps. WTF? How could that be? It seems as though someone is stretching the HP rating a bit. Didn't the small gas engine companies get busted for lying about their HP? Depends on the voltage. And power factor. Flexible cables are higher rated than fixed cables. |
#12
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Horsepower of electric motor V/S Size of motor
On 11/30/2011 9:01 AM, bud-- wrote:
On 11/30/2011 3:46 AM, harry wrote: On Nov 30, 5:03 am, wrote: I have a 1/2HP electric motor on a power saw, and that motor is fairly large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... Thanks The technology of motor has has improved vastly over the years. Better, more heat resistant/thinner insulation, better magnetic matrials, better design, Smaller clearance between stator and rotor. Result, smaller and cheaper motor. Adding to that, motor design was pushed closer to the electrical design edge to make cheaper motors. (Some of that has been reversed in high efficiency motors.) Many years ago the standard 'frame size' was reduced a couple times if I remember right. If the saw has a motor that is quite old it may be larger than an equivalent motor made now. Some motors have a "service factor" rating (maybe 1.15). That means the motor can be operated beyond its rated HP with a somewhat shorter life but not drastically shorter life. I never looked, but motors with a SF rating may be larger. Motors have a nameplate "duty" rating, usually "continuous". Sjouke suggests the pump may have an intermittent rating. Then there is the deliberate misrating of motors, as was done for instance by compressor manufacturers. HP equivalent to Watts. HP =speed of motor X torque x a conversion factor In case that isn't clear, lower RPM motors are likely larger for the same HP. ... An electric motor size is limited only by heat losses and ability to disperse them. There are limits, like saturating the magnetic material. I go through a lot of electric motors at times and air handlers in some of the older commercial buildings will have these huge 1/2 to 1hp cast iron frame motors that are infinitely rebuildable as long as the casting isn't cracked or wallowed out. The motor rewind shops I deal with usually keep a few already rewound in stock. Some years back, I had to remove for rewinding, a 60hp 444S frame motor from a 60 ton open drive air conditioner compressor and the old 60 horse was the same size as a modern 100hp electric motor. I actually found the guy who had rewound the motor 20 years before, he remembered it and rewound it again. ^_^ TDD |
#13
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Horsepower of electric motor V/S Size of motor
On Dec 1, 11:57*pm, The Daring Dufas
wrote: On 11/30/2011 9:01 AM, bud-- wrote: On 11/30/2011 3:46 AM, harry wrote: On Nov 30, 5:03 am, wrote: I have a 1/2HP electric motor on a power saw, and that motor is fairly large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... Thanks The technology of motor has has improved vastly over the years. Better, more heat resistant/thinner insulation, better magnetic matrials, better design, Smaller clearance between stator and rotor. Result, smaller and cheaper motor. Adding to that, motor design was pushed closer to the electrical design edge to make cheaper motors. (Some of that has been reversed in high efficiency motors.) Many years ago the standard 'frame size' was reduced a couple times if I remember right. If the saw has a motor that is quite old it may be larger than an equivalent motor made now. Some motors have a "service factor" rating (maybe 1.15). That means the motor can be operated beyond its rated HP with a somewhat shorter life but not drastically shorter life. I never looked, but motors with a SF rating may be larger. Motors have a nameplate "duty" rating, usually "continuous". Sjouke suggests the pump may have an intermittent rating. Then there is the deliberate misrating of motors, as was done for instance by compressor manufacturers. HP equivalent to Watts. HP =speed of motor X torque x a conversion factor In case that isn't clear, lower RPM motors are likely larger for the same HP. ... An electric motor size is limited only by heat losses and ability to disperse them. There are limits, like saturating the magnetic material. I go through a lot of electric motors at times and air handlers in some of the older commercial buildings will have these huge 1/2 to 1hp cast iron frame motors that are infinitely rebuildable as long as the casting isn't cracked or wallowed out. The motor rewind shops I deal with usually keep a few already rewound in stock. Some years back, I had to remove for rewinding, a 60hp 444S frame motor from a 60 ton open drive air conditioner compressor and the old 60 horse was the same size as a modern 100hp electric motor. I actually found the guy who had rewound the motor 20 years before, he remembered it and rewound it again. ^_^ TDD- Hide quoted text - - Show quoted text - I think most of the motor rewind places over here have closed down. Cheaper to junk them and replace. A lot of the new ones can't b erewound. |
#14
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Horsepower of electric motor V/S Size of motor
On 12/2/2011 7:02 AM, harry wrote:
On Dec 1, 11:57 pm, The Daring wrote: On 11/30/2011 9:01 AM, bud-- wrote: On 11/30/2011 3:46 AM, harry wrote: On Nov 30, 5:03 am, wrote: I have a 1/2HP electric motor on a power saw, and that motor is fairly large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... Thanks The technology of motor has has improved vastly over the years. Better, more heat resistant/thinner insulation, better magnetic matrials, better design, Smaller clearance between stator and rotor. Result, smaller and cheaper motor. Adding to that, motor design was pushed closer to the electrical design edge to make cheaper motors. (Some of that has been reversed in high efficiency motors.) Many years ago the standard 'frame size' was reduced a couple times if I remember right. If the saw has a motor that is quite old it may be larger than an equivalent motor made now. Some motors have a "service factor" rating (maybe 1.15). That means the motor can be operated beyond its rated HP with a somewhat shorter life but not drastically shorter life. I never looked, but motors with a SF rating may be larger. Motors have a nameplate "duty" rating, usually "continuous". Sjouke suggests the pump may have an intermittent rating. Then there is the deliberate misrating of motors, as was done for instance by compressor manufacturers. HP equivalent to Watts. HP =speed of motor X torque x a conversion factor In case that isn't clear, lower RPM motors are likely larger for the same HP. ... An electric motor size is limited only by heat losses and ability to disperse them. There are limits, like saturating the magnetic material. I go through a lot of electric motors at times and air handlers in some of the older commercial buildings will have these huge 1/2 to 1hp cast iron frame motors that are infinitely rebuildable as long as the casting isn't cracked or wallowed out. The motor rewind shops I deal with usually keep a few already rewound in stock. Some years back, I had to remove for rewinding, a 60hp 444S frame motor from a 60 ton open drive air conditioner compressor and the old 60 horse was the same size as a modern 100hp electric motor. I actually found the guy who had rewound the motor 20 years before, he remembered it and rewound it again. ^_^ TDD- Hide quoted text - - Show quoted text - I think most of the motor rewind places over here have closed down. Cheaper to junk them and replace. A lot of the new ones can't b erewound. My first job out of college was working for an electrical supply company that also had an electric motor repair and rewind shop. The company supplied industry throughout that area of the state. Repair and rewinding of electric motors is still a big business around here. TDD |
#15
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Horsepower of electric motor V/S Size of motor
On Nov 30, 12:03*am, wrote:
How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? *Is there another factor to take into account besides the HP? *Is it torque, or some other factor? *Somehow I cant see how this small pump motor could power my saw.... There is no standard ratings system for tool and appliance motors, and manufacturers use fuzzy math to make their products look more powerful than they really are. Just look at vacuum cleaners. You go to Kmart and pick up some cheap plastic Hoover that boasts "2.5 HP" or some such... Plug it into the WattsUp meter at home and it might draw 7 Amps when it's trying to inhale the fringe throw rug. 7 Amps at 120V is nowhere near 2.5 HP. You couldn't put 2.5 HP worth of power through the 15A electrical circuit you have it plugged into. They rated the motor by how many Amps it is drawing just before it stalls and burns out. |
#16
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Horsepower of electric motor V/S Size of motor
On Dec 2, 1:54*pm, The Daring Dufas
wrote: On 12/2/2011 7:02 AM, harry wrote: On Dec 1, 11:57 pm, The Daring wrote: On 11/30/2011 9:01 AM, bud-- wrote: On 11/30/2011 3:46 AM, harry wrote: On Nov 30, 5:03 am, wrote: I have a 1/2HP electric motor on a power saw, and that motor is fairly large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... Thanks The technology of motor has has improved vastly over the years. Better, more heat resistant/thinner insulation, better magnetic matrials, better design, Smaller clearance between stator and rotor. Result, smaller and cheaper motor. Adding to that, motor design was pushed closer to the electrical design edge to make cheaper motors. (Some of that has been reversed in high efficiency motors.) Many years ago the standard 'frame size' was reduced a couple times if I remember right. If the saw has a motor that is quite old it may be larger than an equivalent motor made now. Some motors have a "service factor" rating (maybe 1.15). That means the motor can be operated beyond its rated HP with a somewhat shorter life but not drastically shorter life. I never looked, but motors with a SF rating may be larger. Motors have a nameplate "duty" rating, usually "continuous". Sjouke suggests the pump may have an intermittent rating. Then there is the deliberate misrating of motors, as was done for instance by compressor manufacturers. HP equivalent to Watts. HP =speed of motor X torque x a conversion factor In case that isn't clear, lower RPM motors are likely larger for the same HP. ... An electric motor size is limited only by heat losses and ability to disperse them. There are limits, like saturating the magnetic material. I go through a lot of electric motors at times and air handlers in some of the older commercial buildings will have these huge 1/2 to 1hp cast iron frame motors that are infinitely rebuildable as long as the casting isn't cracked or wallowed out. The motor rewind shops I deal with usually keep a few already rewound in stock. Some years back, I had to remove for rewinding, a 60hp 444S frame motor from a 60 ton open drive air conditioner compressor and the old 60 horse was the same size as a modern 100hp electric motor. I actually found the guy who had rewound the motor 20 years before, he remembered it and rewound it again. ^_^ TDD- Hide quoted text - - Show quoted text - I think most of the motor rewind places over here have closed down. Cheaper to junk them and replace. A lot of the new ones can't b erewound. My first job out of college was working for an electrical supply company that also had an electric motor repair and rewind shop. The company supplied industry throughout that area of the state. Repair and rewinding of electric motors is still a big business around here. TDD- Hide quoted text - - Show quoted text - Only large motors here are rewound. Just not economical to do the small ones. A lot have the windings set in resin, very difficult to do anything with. They seem to be much more reliable than in days of yore. |
#17
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Horsepower of electric motor V/S Size of motor
On 12/2/2011 2:31 PM, harry wrote:
On Dec 2, 1:54 pm, The Daring wrote: On 12/2/2011 7:02 AM, harry wrote: On Dec 1, 11:57 pm, The Daring wrote: On 11/30/2011 9:01 AM, bud-- wrote: On 11/30/2011 3:46 AM, harry wrote: On Nov 30, 5:03 am, wrote: I have a 1/2HP electric motor on a power saw, and that motor is fairly large. I just bought a portable pump for transferring water from items such as a flooded washing machine, bathtub with clogged drain, etc. That motor is only about 35% of the size of the motor on my power saw, yet the tag says it's a 1/2HP motor. How can one 1/2HP motor less than half the size of another 1/2HP motor produce the same horsepower? Is there another factor to take into account besides the HP? Is it torque, or some other factor? Somehow I cant see how this small pump motor could power my saw.... Thanks The technology of motor has has improved vastly over the years. Better, more heat resistant/thinner insulation, better magnetic matrials, better design, Smaller clearance between stator and rotor. Result, smaller and cheaper motor. Adding to that, motor design was pushed closer to the electrical design edge to make cheaper motors. (Some of that has been reversed in high efficiency motors.) Many years ago the standard 'frame size' was reduced a couple times if I remember right. If the saw has a motor that is quite old it may be larger than an equivalent motor made now. Some motors have a "service factor" rating (maybe 1.15). That means the motor can be operated beyond its rated HP with a somewhat shorter life but not drastically shorter life. I never looked, but motors with a SF rating may be larger. Motors have a nameplate "duty" rating, usually "continuous". Sjouke suggests the pump may have an intermittent rating. Then there is the deliberate misrating of motors, as was done for instance by compressor manufacturers. HP equivalent to Watts. HP =speed of motor X torque x a conversion factor In case that isn't clear, lower RPM motors are likely larger for the same HP. ... An electric motor size is limited only by heat losses and ability to disperse them. There are limits, like saturating the magnetic material. I go through a lot of electric motors at times and air handlers in some of the older commercial buildings will have these huge 1/2 to 1hp cast iron frame motors that are infinitely rebuildable as long as the casting isn't cracked or wallowed out. The motor rewind shops I deal with usually keep a few already rewound in stock. Some years back, I had to remove for rewinding, a 60hp 444S frame motor from a 60 ton open drive air conditioner compressor and the old 60 horse was the same size as a modern 100hp electric motor. I actually found the guy who had rewound the motor 20 years before, he remembered it and rewound it again. ^_^ TDD- Hide quoted text - - Show quoted text - I think most of the motor rewind places over here have closed down. Cheaper to junk them and replace. A lot of the new ones can't b erewound. My first job out of college was working for an electrical supply company that also had an electric motor repair and rewind shop. The company supplied industry throughout that area of the state. Repair and rewinding of electric motors is still a big business around here. TDD- Hide quoted text - - Show quoted text - Only large motors here are rewound. Just not economical to do the small ones. A lot have the windings set in resin, very difficult to do anything with. They seem to be much more reliable than in days of yore. The regular split phase, capacitor start and capacitor run motors in standard sizes and frames aren't usually rewound, they're scrapped but there are a lot of smaller motors that have no direct replacement and those are the ones that are rewound. I often send small DC drive armatures off to be rewound to a place in Tampa, Florida. They're good with the very small DC motors like those in 90 vdc drives. http://www.southernwinding.com/ I have had larger armatures rewound locally but no one around here is as good with the smaller drives. Automotive starters, generators and alternators are also remanufactured and repaired all around here. TDD |
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