The other day I'm helping the boss do a resterunt. runing the wire for the hood vent motor he said we need to make sure it tuns the right way (240v 1 phase). I said I don't think it maters on 1 phase. so I hooked it up it went CC (as your are looking at the shaft)that is good. but me wanting to know more swaped the legs at the braker, still CC. so my question is does it matter on 1 phase? how dose this work in a motor?
motor rotation
- Thread starter wyatt
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growler
Senior Member
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- Atlanta,GA
Re: motor rotation
I would add something. It does matter which direction the motor turns. Whith the new vent hoods one of the fans supply fresh air and the others suck out the smoke and steam. The direction needed is normally marked. The point I wanted to make, Don't trust what is marked on the unit for voltage, check the motor taps yourself and make sure it's tapped for 240. Those are dual voltage motors and they will mark the unit any way they feel like. We had some marked 240 but were tapped 120. Get this, from the switches on the front of the hood to the junction box on top they used all green wires ( factory job ). PS motor rotation is judged from the back of the motor. Clockwise means that it turns clockwise looking at it from the rear.
I would add something. It does matter which direction the motor turns. Whith the new vent hoods one of the fans supply fresh air and the others suck out the smoke and steam. The direction needed is normally marked. The point I wanted to make, Don't trust what is marked on the unit for voltage, check the motor taps yourself and make sure it's tapped for 240. Those are dual voltage motors and they will mark the unit any way they feel like. We had some marked 240 but were tapped 120. Get this, from the switches on the front of the hood to the junction box on top they used all green wires ( factory job ). PS motor rotation is judged from the back of the motor. Clockwise means that it turns clockwise looking at it from the rear.
B
bthielen
Guest
Re: motor rotation
growler,
Is motor rotation as you have defined it and industry standard or your experience as typical? I'm not questioning your integrity, just trying to clear this up for myself because I have struggled with this for years. Especially when it comes to servo motors. The manufacturers will tell you that out of the box the feedback will be positive for clockwise motor rotation but I usually find they don't define clockwise. I assumed that it must be because there is a standard but I have not been able to find any documents to support it.
Bob
growler,
Is motor rotation as you have defined it and industry standard or your experience as typical? I'm not questioning your integrity, just trying to clear this up for myself because I have struggled with this for years. Especially when it comes to servo motors. The manufacturers will tell you that out of the box the feedback will be positive for clockwise motor rotation but I usually find they don't define clockwise. I assumed that it must be because there is a standard but I have not been able to find any documents to support it.
Bob
- Location
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- Semi-Retired Electrical Engineer
Re: motor rotation
The bit about "swapping wires to change rotation" only applies to three-phase motors. It is not easy to explain how or why that works, without a white board. But what happens in a three phase motor is that the current in the stator creates a magnetic field, and causes the field to rotate around the axis. That field, in turn, causes the rotor to turn. If you exchange any two of the wires to the motor, the magnetic field will rotate in the opposite direction. That would, of course, cause the motor to run backwards.
The bit about "swapping wires to change rotation" only applies to three-phase motors. It is not easy to explain how or why that works, without a white board. But what happens in a three phase motor is that the current in the stator creates a magnetic field, and causes the field to rotate around the axis. That field, in turn, causes the rotor to turn. If you exchange any two of the wires to the motor, the magnetic field will rotate in the opposite direction. That would, of course, cause the motor to run backwards.
Re: motor rotation
Two things:
First, I have always determined CW or CCW rotation on a motor as if i sat on the motor like I would a horse; with the head of the horse being the shaft end and the tail being the fan end. Once you visualize that you are sitting on the motor looking at the shaft; you can determine CW or CCW direction. Corny yes, but has not failed me yet if my memory serves me correctly.
Second, when you change direction of a single phase motor by swapping T5 & T8, in effect you are changing the direction of current flow of the Start winding in relation to the Run winding. Swapping both the line leads will not change the relation between them and will not change direction of the motor.
This also applies to DC motors except you are changing the relation between the Armature winding and Field winding to change motor direction. You are not swapping the line leads, but one winding's wires as it relates to the other winding.
Hope this helps
Two things:
First, I have always determined CW or CCW rotation on a motor as if i sat on the motor like I would a horse; with the head of the horse being the shaft end and the tail being the fan end. Once you visualize that you are sitting on the motor looking at the shaft; you can determine CW or CCW direction. Corny yes, but has not failed me yet if my memory serves me correctly.
Second, when you change direction of a single phase motor by swapping T5 & T8, in effect you are changing the direction of current flow of the Start winding in relation to the Run winding. Swapping both the line leads will not change the relation between them and will not change direction of the motor.
This also applies to DC motors except you are changing the relation between the Armature winding and Field winding to change motor direction. You are not swapping the line leads, but one winding's wires as it relates to the other winding.
Hope this helps
Re: motor rotation
Yes it is standard when you talk to any motor head to determine rotation by looking at the ODE, (Opposite drive end). No I've never seen it written anywhere, but every motor tech, rewinder, salesmen, designer I have ever talked to used that.
Single phase motor swap 5 & 8, these are not the line leads, they go to the start windings. Once a single phase motor is running the start winding is dropped out. and things are spinning so fast they keep going that way. Rotation is set up by which way it starts out. I have had many single phase start windings go and the equipment still had to run. Grab the shaft and spin it either way and away it will go.
To add, a single phase motor does not operate exactly the same as a three phase. It does not really set up a rotating field. Once it is running the fields just flop back and forth. Would definitely need a white board to explain how this happens.
[ March 02, 2006, 11:53 AM: Message edited by: 69boss302 ]
Yes it is standard when you talk to any motor head to determine rotation by looking at the ODE, (Opposite drive end). No I've never seen it written anywhere, but every motor tech, rewinder, salesmen, designer I have ever talked to used that.
Single phase motor swap 5 & 8, these are not the line leads, they go to the start windings. Once a single phase motor is running the start winding is dropped out. and things are spinning so fast they keep going that way. Rotation is set up by which way it starts out. I have had many single phase start windings go and the equipment still had to run. Grab the shaft and spin it either way and away it will go.
To add, a single phase motor does not operate exactly the same as a three phase. It does not really set up a rotating field. Once it is running the fields just flop back and forth. Would definitely need a white board to explain how this happens.
[ March 02, 2006, 11:53 AM: Message edited by: 69boss302 ]
growler
Senior Member
- Location
- Atlanta,GA
Re: motor rotation
I stated what I was trying to say wrong but I did mean well. I'm glad 69Boss302 cleared that up. According to NEMA the opposite Drive End is actually the front of the motor ( I forgot that ). I believe that the NEMA standard for motor rotation is from the front and it is a standard. When I called the ODE the rear I was wrong.
I stated what I was trying to say wrong but I did mean well. I'm glad 69Boss302 cleared that up. According to NEMA the opposite Drive End is actually the front of the motor ( I forgot that ). I believe that the NEMA standard for motor rotation is from the front and it is a standard. When I called the ODE the rear I was wrong.
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- PE (Retired) - Power Systems
Re: motor rotation
My copy of the Electrical Engineering Pocket Handbook published by the Electrical Apparatus Service Association (EASA) has a written sentence:
"The direction of shaft rotation can be determined by facing the end of the motor opposite the drive."
My copy of the Electrical Engineering Pocket Handbook published by the Electrical Apparatus Service Association (EASA) has a written sentence:
"The direction of shaft rotation can be determined by facing the end of the motor opposite the drive."
Re: motor rotation
Now here's something that i've been doing for a while that works on 3 phase ac motors only.Exception is on freq. drives because they have phase rotation sensors.If you look at the direction you want the pully to travel and say its clockwise ,and know that your incoming line abc is clockwise, then hook up the line 1-2-3 on the motor as is. if your abc rotation is counter clockwise,then swap any line at the motor before terminating .This puts the 50-50 theory out the door.Have you guy's had the similar results?
Rick
Now here's something that i've been doing for a while that works on 3 phase ac motors only.Exception is on freq. drives because they have phase rotation sensors.If you look at the direction you want the pully to travel and say its clockwise ,and know that your incoming line abc is clockwise, then hook up the line 1-2-3 on the motor as is. if your abc rotation is counter clockwise,then swap any line at the motor before terminating .This puts the 50-50 theory out the door.Have you guy's had the similar results?
Rick
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