Bypass current of parallel conected inductor/diode

In summary, the conversation discusses the calculation of bypass diode current on a superconducting coil. The coil's self-inductance and the resistor's resistance are mentioned, and an equation is provided for when there is no bypass diode. However, the inclusion of the bypass diode leads to a discrepancy in energy conservation and the simulator does not accurately reflect this. The possibility of a "dump resistor" as a way to dissipate energy is also mentioned.
  • #1
hsinhui
3
0
Hello, good day!

I am stuck on the bypass diode current calculation on superconducting coil
The connection is as following.

->------Inductor(L)---Resistor(R)------>-
| |
-->------Bypass Diode---->----

The resistor R is the increasing quenched zone resistance.
The inductor L is the superconducting coil self-inductance.

If there is no bypass diode and coil is in persistent mode.
L*(di/dt)+i*R=0, i:coil current, t: time
i=i0*exp(-Rt/L), i0: coil initial current @t=0

But if the bypass diode is connected.
L*(di/dt)+i*R=VD, VD: diode voltage
i=i0*exp(-Rt/L)*(exp(Rt/L)-1)*(VD/R)

I simulated the coil current with the equation above.
The coil current is bypassed to diode instantly.
But this scenario is not true for the energy conservation.
The inductor stored energy (1.25MJ) can not be consumed so fast.

I miss something in my model.
If anybody can help me to figure out what happens?

Thanks a lot!
 
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  • #2
hsinhui said:
I simulated the coil current with the equation above.
The coil current is bypassed to diode instantly.
But this scenario is not true for the energy conservation.
The inductor stored energy (1.25MJ) can not be consumed so fast.
Right. Your resistor is the dump resistor if the magnet quenches and "dump resistor" might be something like drums of water connected by a steel bar to dissipate the energy. It is true for energy conservation because the dump resistor is where the energy is dissipated.
 

1. What is a bypass current?

A bypass current is an electrical current that flows through a parallel path in a circuit, bypassing the main path. This can occur when there is a lower resistance path available, such as through a parallel connected inductor and diode.

2. How does a parallel connected inductor and diode create a bypass current?

A parallel connected inductor and diode create a bypass current by providing a lower resistance path for the electrical current to flow through. When the inductor is energized, it stores energy in its magnetic field. When the inductor is de-energized, it releases this stored energy. The diode allows this energy to flow through, creating a bypass current.

3. Why is a bypass current undesirable?

A bypass current can cause problems in a circuit by altering the current and voltage levels. This can lead to malfunction or damage to components. It can also affect the overall efficiency of the circuit.

4. How can a bypass current be controlled in a circuit?

A bypass current can be controlled by adding a resistor in series with the inductor and diode. This will limit the amount of current that can flow through the bypass path. Additionally, using a higher quality diode with better switching characteristics can also help reduce bypass current.

5. What are some applications of controlling bypass current in parallel connected inductor/diode circuits?

Controlling bypass current in parallel connected inductor/diode circuits is important in various electronic devices, such as power supplies, where stable and efficient current and voltage levels are crucial. It is also used in applications where the inductor and diode are used for energy storage, such as in DC-DC converters and battery charging systems.

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