Why is it harder to turn a motor/generator with shorted terminals?24V H-Bridge DC motor, why voltage drop to 3v if motor connecteddriving a synchronous motor as a generatorDriving BLDC motor directly from GeneratorRotate BLDC motor with Clark and Park transformWhy does the stator field rotate at the same speed as the rotor field in a synchronous generator?How to allow a motor to free spin?Torque control of a BLDC motor acting as a generatorgear motor can be used as generatorDc motor as torque transducer for BLDC motorWhy does shorting the phases of a BLDC motor cause it to lock?
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Why is it harder to turn a motor/generator with shorted terminals?
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Why is it harder to turn a motor/generator with shorted terminals?
24V H-Bridge DC motor, why voltage drop to 3v if motor connecteddriving a synchronous motor as a generatorDriving BLDC motor directly from GeneratorRotate BLDC motor with Clark and Park transformWhy does the stator field rotate at the same speed as the rotor field in a synchronous generator?How to allow a motor to free spin?Torque control of a BLDC motor acting as a generatorgear motor can be used as generatorDc motor as torque transducer for BLDC motorWhy does shorting the phases of a BLDC motor cause it to lock?
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
$begingroup$
The shaft of an unconnected motor is relatively easy to rotate relative to the motor with shorted terminals. If a resistive load is connected to the terminals, the turning difficulty is somewhere in between. I'm using a BLDC motor.
Why is this?
motor dc-motor generator
asked 1 hour ago
abcabc
317212
$endgroup$
add a comment |
$begingroup$
The shaft of an unconnected motor is relatively easy to rotate relative to the motor with shorted terminals. If a resistive load is connected to the terminals, the turning difficulty is somewhere in between. I'm using a BLDC motor.
Why is this?
motor dc-motor generator
asked 1 hour ago
abcabc
317212
$endgroup$
$begingroup$
Normally electrical power sources are constant voltage, so a load with a smaller resistance is considered to be a larger load. Could you edit your title, please?
$endgroup$
– TimWescott
1 hour ago
$begingroup$
Not in my my experience, shorted terminals is more difficult with a permanent magnet DC brushed or BLDC motor. Be specific about the type of motor you are using.
$endgroup$
– Neil_UK
1 hour ago
$begingroup$
@Neil_UK I agree with you. I think that's what I stated in the description.
$endgroup$
– abc
1 hour ago
add a comment |
$begingroup$
The shaft of an unconnected motor is relatively easy to rotate relative to the motor with shorted terminals. If a resistive load is connected to the terminals, the turning difficulty is somewhere in between. I'm using a BLDC motor.
Why is this?
motor dc-motor generator
asked 1 hour ago
abcabc
317212
$endgroup$
The shaft of an unconnected motor is relatively easy to rotate relative to the motor with shorted terminals. If a resistive load is connected to the terminals, the turning difficulty is somewhere in between. I'm using a BLDC motor.
Why is this?
motor dc-motor generator
motor dc-motor generator
asked 1 hour ago
abcabc
317212
asked 1 hour ago
abcabc
317212
edited 1 hour ago
abc
asked 1 hour ago
abcabc
317212
asked 1 hour ago
abcabc
317212
asked 1 hour ago
abcabc
317212
317212
$begingroup$
Normally electrical power sources are constant voltage, so a load with a smaller resistance is considered to be a larger load. Could you edit your title, please?
$endgroup$
– TimWescott
1 hour ago
$begingroup$
Not in my my experience, shorted terminals is more difficult with a permanent magnet DC brushed or BLDC motor. Be specific about the type of motor you are using.
$endgroup$
– Neil_UK
1 hour ago
$begingroup$
@Neil_UK I agree with you. I think that's what I stated in the description.
$endgroup$
– abc
1 hour ago
add a comment |
$begingroup$
Normally electrical power sources are constant voltage, so a load with a smaller resistance is considered to be a larger load. Could you edit your title, please?
$endgroup$
– TimWescott
1 hour ago
$begingroup$
Not in my my experience, shorted terminals is more difficult with a permanent magnet DC brushed or BLDC motor. Be specific about the type of motor you are using.
$endgroup$
– Neil_UK
1 hour ago
$begingroup$
@Neil_UK I agree with you. I think that's what I stated in the description.
$endgroup$
– abc
1 hour ago
$begingroup$
Normally electrical power sources are constant voltage, so a load with a smaller resistance is considered to be a larger load. Could you edit your title, please?
$endgroup$
– TimWescott
1 hour ago
$begingroup$
Normally electrical power sources are constant voltage, so a load with a smaller resistance is considered to be a larger load. Could you edit your title, please?
$endgroup$
– TimWescott
1 hour ago
$begingroup$
Not in my my experience, shorted terminals is more difficult with a permanent magnet DC brushed or BLDC motor. Be specific about the type of motor you are using.
$endgroup$
– Neil_UK
1 hour ago
$begingroup$
Not in my my experience, shorted terminals is more difficult with a permanent magnet DC brushed or BLDC motor. Be specific about the type of motor you are using.
$endgroup$
– Neil_UK
1 hour ago
$begingroup$
@Neil_UK I agree with you. I think that's what I stated in the description.
$endgroup$
– abc
1 hour ago
$begingroup$
@Neil_UK I agree with you. I think that's what I stated in the description.
$endgroup$
– abc
1 hour ago
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
I have to start with some terminology -- sorry if it's esoteric, but this will bring things into line with how folks talk about this subject.
When you turn a permanent-magnet DC machine*, the armature generates a voltage internally. This is called the "EMF"** of the armature, or the "back EMF" if the machine is running as a motor. This EMF is always generated when the machine turns.
When you run current through a DC machine, it generates a torque. This torque is always generated when the machine turns, regardless of whether it's a motor or a generator.
When you put a resistance on the terminals of a machine and turn its shaft, it generates that EMF. With the resistance connected, this EMF causes a current to flow that's proportional to the EMF divided by the external resistance plus the machine's armature resistance. This current, in turn, generates a torque that resists motion (due to conservation of energy, it must be in a direction to resist motion).
Shorting the machine puts the smallest possible resistance on it -- you can't get lower than 0 without resorting to active circuitry. The back torque in this case is purely a product of the EMF and the armature resistance. Increasing the resistance by putting a resistor on there means less current for the same machine speed, which means less back torque. In the extreme, you have no resistor at all, which means infinite electrical resistance -- this means that the back torque will be from mechanical effects such as friction (and windage, if you're turning it that fast), and possibly mechanical and electromechanical effects as the field magnets work against the iron in the armature.
* I'm calling it a "machine" instead of a "motor" because it can be a motor or a generator, depending on how you use it. But you don't have to change anything internally to change how it's used -- hence, "machine".
** EMF stands for "electromotive force", which is just and older term for "voltage". It seems silly to have two terms, but sometimes it's useful.
answered 1 hour ago
TimWescottTimWescott
8,0991417
$endgroup$
$begingroup$
I appreciate the fundamental explanation. I find a lot of information regarding the "whats" of DC motor operation, but the "whys" are harder to come by.
$endgroup$
– abc
29 mins ago
add a comment |
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1 Answer
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1 Answer
1
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active
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active
oldest
votes
$begingroup$
I have to start with some terminology -- sorry if it's esoteric, but this will bring things into line with how folks talk about this subject.
When you turn a permanent-magnet DC machine*, the armature generates a voltage internally. This is called the "EMF"** of the armature, or the "back EMF" if the machine is running as a motor. This EMF is always generated when the machine turns.
When you run current through a DC machine, it generates a torque. This torque is always generated when the machine turns, regardless of whether it's a motor or a generator.
When you put a resistance on the terminals of a machine and turn its shaft, it generates that EMF. With the resistance connected, this EMF causes a current to flow that's proportional to the EMF divided by the external resistance plus the machine's armature resistance. This current, in turn, generates a torque that resists motion (due to conservation of energy, it must be in a direction to resist motion).
Shorting the machine puts the smallest possible resistance on it -- you can't get lower than 0 without resorting to active circuitry. The back torque in this case is purely a product of the EMF and the armature resistance. Increasing the resistance by putting a resistor on there means less current for the same machine speed, which means less back torque. In the extreme, you have no resistor at all, which means infinite electrical resistance -- this means that the back torque will be from mechanical effects such as friction (and windage, if you're turning it that fast), and possibly mechanical and electromechanical effects as the field magnets work against the iron in the armature.
* I'm calling it a "machine" instead of a "motor" because it can be a motor or a generator, depending on how you use it. But you don't have to change anything internally to change how it's used -- hence, "machine".
** EMF stands for "electromotive force", which is just and older term for "voltage". It seems silly to have two terms, but sometimes it's useful.
answered 1 hour ago
TimWescottTimWescott
8,0991417
$endgroup$
$begingroup$
I appreciate the fundamental explanation. I find a lot of information regarding the "whats" of DC motor operation, but the "whys" are harder to come by.
$endgroup$
– abc
29 mins ago
add a comment |
$begingroup$
I have to start with some terminology -- sorry if it's esoteric, but this will bring things into line with how folks talk about this subject.
When you turn a permanent-magnet DC machine*, the armature generates a voltage internally. This is called the "EMF"** of the armature, or the "back EMF" if the machine is running as a motor. This EMF is always generated when the machine turns.
When you run current through a DC machine, it generates a torque. This torque is always generated when the machine turns, regardless of whether it's a motor or a generator.
When you put a resistance on the terminals of a machine and turn its shaft, it generates that EMF. With the resistance connected, this EMF causes a current to flow that's proportional to the EMF divided by the external resistance plus the machine's armature resistance. This current, in turn, generates a torque that resists motion (due to conservation of energy, it must be in a direction to resist motion).
Shorting the machine puts the smallest possible resistance on it -- you can't get lower than 0 without resorting to active circuitry. The back torque in this case is purely a product of the EMF and the armature resistance. Increasing the resistance by putting a resistor on there means less current for the same machine speed, which means less back torque. In the extreme, you have no resistor at all, which means infinite electrical resistance -- this means that the back torque will be from mechanical effects such as friction (and windage, if you're turning it that fast), and possibly mechanical and electromechanical effects as the field magnets work against the iron in the armature.
* I'm calling it a "machine" instead of a "motor" because it can be a motor or a generator, depending on how you use it. But you don't have to change anything internally to change how it's used -- hence, "machine".
** EMF stands for "electromotive force", which is just and older term for "voltage". It seems silly to have two terms, but sometimes it's useful.
answered 1 hour ago
TimWescottTimWescott
8,0991417
$endgroup$
$begingroup$
I appreciate the fundamental explanation. I find a lot of information regarding the "whats" of DC motor operation, but the "whys" are harder to come by.
$endgroup$
– abc
29 mins ago
add a comment |
$begingroup$
I have to start with some terminology -- sorry if it's esoteric, but this will bring things into line with how folks talk about this subject.
When you turn a permanent-magnet DC machine*, the armature generates a voltage internally. This is called the "EMF"** of the armature, or the "back EMF" if the machine is running as a motor. This EMF is always generated when the machine turns.
When you run current through a DC machine, it generates a torque. This torque is always generated when the machine turns, regardless of whether it's a motor or a generator.
When you put a resistance on the terminals of a machine and turn its shaft, it generates that EMF. With the resistance connected, this EMF causes a current to flow that's proportional to the EMF divided by the external resistance plus the machine's armature resistance. This current, in turn, generates a torque that resists motion (due to conservation of energy, it must be in a direction to resist motion).
Shorting the machine puts the smallest possible resistance on it -- you can't get lower than 0 without resorting to active circuitry. The back torque in this case is purely a product of the EMF and the armature resistance. Increasing the resistance by putting a resistor on there means less current for the same machine speed, which means less back torque. In the extreme, you have no resistor at all, which means infinite electrical resistance -- this means that the back torque will be from mechanical effects such as friction (and windage, if you're turning it that fast), and possibly mechanical and electromechanical effects as the field magnets work against the iron in the armature.
* I'm calling it a "machine" instead of a "motor" because it can be a motor or a generator, depending on how you use it. But you don't have to change anything internally to change how it's used -- hence, "machine".
** EMF stands for "electromotive force", which is just and older term for "voltage". It seems silly to have two terms, but sometimes it's useful.
answered 1 hour ago
TimWescottTimWescott
8,0991417
$endgroup$
I have to start with some terminology -- sorry if it's esoteric, but this will bring things into line with how folks talk about this subject.
When you turn a permanent-magnet DC machine*, the armature generates a voltage internally. This is called the "EMF"** of the armature, or the "back EMF" if the machine is running as a motor. This EMF is always generated when the machine turns.
When you run current through a DC machine, it generates a torque. This torque is always generated when the machine turns, regardless of whether it's a motor or a generator.
When you put a resistance on the terminals of a machine and turn its shaft, it generates that EMF. With the resistance connected, this EMF causes a current to flow that's proportional to the EMF divided by the external resistance plus the machine's armature resistance. This current, in turn, generates a torque that resists motion (due to conservation of energy, it must be in a direction to resist motion).
Shorting the machine puts the smallest possible resistance on it -- you can't get lower than 0 without resorting to active circuitry. The back torque in this case is purely a product of the EMF and the armature resistance. Increasing the resistance by putting a resistor on there means less current for the same machine speed, which means less back torque. In the extreme, you have no resistor at all, which means infinite electrical resistance -- this means that the back torque will be from mechanical effects such as friction (and windage, if you're turning it that fast), and possibly mechanical and electromechanical effects as the field magnets work against the iron in the armature.
* I'm calling it a "machine" instead of a "motor" because it can be a motor or a generator, depending on how you use it. But you don't have to change anything internally to change how it's used -- hence, "machine".
** EMF stands for "electromotive force", which is just and older term for "voltage". It seems silly to have two terms, but sometimes it's useful.
answered 1 hour ago
TimWescottTimWescott
8,0991417
answered 1 hour ago
TimWescottTimWescott
8,0991417
answered 1 hour ago
TimWescottTimWescott
8,0991417
answered 1 hour ago
TimWescottTimWescott
8,0991417
8,0991417
$begingroup$
I appreciate the fundamental explanation. I find a lot of information regarding the "whats" of DC motor operation, but the "whys" are harder to come by.
$endgroup$
– abc
29 mins ago
add a comment |
$begingroup$
I appreciate the fundamental explanation. I find a lot of information regarding the "whats" of DC motor operation, but the "whys" are harder to come by.
$endgroup$
– abc
29 mins ago
$begingroup$
I appreciate the fundamental explanation. I find a lot of information regarding the "whats" of DC motor operation, but the "whys" are harder to come by.
$endgroup$
– abc
29 mins ago
$begingroup$
I appreciate the fundamental explanation. I find a lot of information regarding the "whats" of DC motor operation, but the "whys" are harder to come by.
$endgroup$
– abc
29 mins ago
add a comment |
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$begingroup$
Normally electrical power sources are constant voltage, so a load with a smaller resistance is considered to be a larger load. Could you edit your title, please?
$endgroup$
– TimWescott
1 hour ago
$begingroup$
Not in my my experience, shorted terminals is more difficult with a permanent magnet DC brushed or BLDC motor. Be specific about the type of motor you are using.
$endgroup$
– Neil_UK
1 hour ago
$begingroup$
@Neil_UK I agree with you. I think that's what I stated in the description.
$endgroup$
– abc
1 hour ago