Motors in series: how do you stop one motor from spinning?

In summary: In that case, I don't see how it would work- you would need to have the electric motor generating more power than the ICE to make it useful.I should've clarified that the drivetrain setup is when the electric motor stator is attached to the ICE's output shaft. The electric motor's rotor is attached to the wheel.
  • #1
sfensphan
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1
Hi All,
I've been reading up on hybrid vehicles and how the Honda Insight has an electric motor attached directly to the gas engine driveshaft. Their combined output causes the wheels to spin. My question is in regards to when the electric motor is off but the gas engine is on. Why doesn't the gas engine just force the electric motor to spin and the wheel to not move? I know there is some gearing involved, but I don't think the setup is non-backdriveable, and I don't believe there is a physical brake that clutches the electric motor. How about in situations where there is just direct drive? Do they just run the motor at a very low setting to prevent the electric motor rotation? That sounds like a stall scenario to me, and that would use a lot of power. How do you just use one of two motors in a serial configuration?

Would love to hear your guys' thoughts. Thanks very much!
 
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  • #2
Why doesn't the gas engine just force the electric motor to spin and the wheel to not move?
... With the electric motor switched off, why wouldn't the drive shaft just turn the motor and the wheels? After all the shaft rotates with the engine, and is connected to both.
Series drivechains are done where both engines are ICE - how does that work if one of the ICEs is not switched on, but not disconnected? Could Honda engineers not use similar solutions?

I don't believe there is a physical brake that clutches the electric motor.
How are you supporting this belief?
 
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  • #3
The engine and motor share a common driveshaft. When the motor is 'off', that just means it is spinning and not supplying power or acting as a regenerative brake. This design adds one bearing to the drive train and requires no additional gears or clutches. Very simple and compact.
 
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  • #4
Simon Bridge said:
... With the electric motor switched off, why wouldn't the drive shaft just turn the motor and the wheels? After all the shaft rotates with the engine, and is connected to both.
Series drivechains are done where both engines are ICE - how does that work if one of the ICEs is not switched on, but not disconnected? Could Honda engineers not use similar solutions?

How are you supporting this belief?

Thanks Simon for taking a look. For your first question, I would expect the switched off motor to rotate (stator rotating with respect to the rotor), sort of acting like a bearing, with no work being done on the wheel itself. With the rotor and stator moving, it is acting like a generator. To lock the rotor and stator together, you would need to always have it on or have a clutch. From what I've read about the car, it doesn't seem to have a clutch in that location.

I'm mostly thinking about 2 motor cars being used in power saving mode or if one motor is broken.
 
  • #5
dschlink said:
The engine and motor share a common driveshaft. When the motor is 'off', that just means it is spinning and not supplying power or acting as a regenerative brake. This design adds one bearing to the drive train and requires no additional gears or clutches. Very simple and compact.
Thanks dschlink. appreciate your thoughts. I should've clarified that the drivetrain setup is when the electric motor stator is attached to the ICE's output shaft. The electric motor's rotor is attached to the wheel. I think i understand the case where the electric motor adds power by a gear. I guess when one motor is off and not acting as a generator (so no back emf), the drag that induces is pretty minimal.
 
  • #6
sfensphan said:
I should've clarified that the drivetrain setup is when the electric motor stator is attached to the ICE's output shaft. The electric motor's rotor is attached to the wheel.

Where have you seen this arrangement used? It sounds like a rather inelegant solution. Your electric motor would need to have a torque output in excess of the ICE output to do any good.

BoB
 
  • #7
sfensphan said:
I should've clarified that the drivetrain setup is when the electric motor stator is attached to the ICE's output shaft. The electric motor's rotor is attached to the wheel.

It's not clear to me what you are describing here. A stator is stationary, and a rotor rotates inside it (on some motors the rotor is outside the stator). But regardless, the rotor and stator are concentric. So having the stator on the ICE output shaft, and the rotor on the wheel, makes no sense.

Maybe you are talking about two motor/generators?
 

1. How does a motor in series work?

A motor in series is a type of circuit where the motor is connected to the power source in a series with other components. This means that the current flows through each component in the circuit, including the motor, in a single path. As a result, the motor will spin as long as there is a current flowing through the circuit.

2. Why would you want to stop one motor from spinning in a series circuit?

There are several reasons why you may want to stop one motor from spinning in a series circuit. One reason could be to control the speed of the motor. By stopping one motor, you can reduce the overall speed of the circuit. Another reason could be to conserve energy or to prevent overheating of the motor.

3. How do you physically stop a motor from spinning in a series circuit?

To physically stop a motor from spinning in a series circuit, you can use a variety of methods. One method is to use a mechanical brake, which physically stops the rotation of the motor. Another method is to use an electronic brake, which interrupts the current flow and stops the motor from receiving power.

4. Can you stop a motor from spinning without stopping the entire circuit?

Yes, it is possible to stop a motor from spinning without stopping the entire circuit. This can be achieved by using a switch or a variable resistor to interrupt the current flow to the motor. This allows you to control the motor's speed and rotation without affecting the rest of the circuit.

5. Are there any safety precautions to consider when stopping a motor in a series circuit?

Yes, there are some safety precautions to consider when stopping a motor in a series circuit. It is important to ensure that the motor is completely disconnected from the power source before attempting to stop it. Additionally, if you are using a mechanical brake, make sure that the motor is properly secured to prevent any accidents or injuries.

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