Circuit is driving me nuts

In summary, the conversation discusses a diagram of a wye connected motor load with open neutral and equations that should hold for the inverter state. The goal is to prove that the back EMFs in each phase can be replaced by the same effective impedance. However, the speaker later realizes that this cannot be proven due to a mistake in their simulation. The conversation ends with the speaker apologizing for any confusion and thanking the listener for their time.
  • #1
milesyoung
818
67
Hi,

I have attached a diagram of a wye connected motor load with open neutral. The circuit shows an inverter state with a DC-bus voltage from terminal A to G (ground). The following equations should hold:

V_AN = Z*Ia + Ea
V_GN = Z*Ib + Eb
V_GN = Z*Ic + Ec
Ia + Ib + Ic = 0
Ea + Eb + Ec = 0 (back EMFs sum to zero)

I want to prove that:

Ea/Ia = Eb/Ib = Ec/Ic

which would mean, according to:

V_AN/Ia = Z + Ea/Ia
V_GN/Ib = Z + Eb/Ib
V_GN/Ic = Z + Ec/Ic

that the impedance + back EMF in each phase can be replaced by the same effective impedance. I have verified this by simulation in LTspice.

This is probably very simple, but it has been bothering me all day. Any help is greatly appreciated.

Thanks!
 

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  • #2
Err, so I made a huge mistake when I did the simulation, Ea/Ia = Eb/Ib = Ec/Ic can't be proven because it doesn't hold :>

I was wondering why the phase voltages for the circuit I posted were the same for a passive circuit with equal phase impedances. This is naturally due to the fact that the phase voltages sum to zero in both cases (when back EMFs sum to zero):

V_AN + 2*V_GN = Z*Ia + Ea + Z*Ib + Eb + Z*Ic + Ec = Z(Ia + Ib + Ic) + Ea + Eb + Ec =>

V_AN + 2*V_GN = 0

which would be the same for the passive circuit.

If you took the time to mull over this, thank you, apologies :)
 

Related to Circuit is driving me nuts

1. What is a circuit?

A circuit is a closed loop or pathway through which electric current can flow.

2. How does a circuit work?

A circuit works by connecting different electrical components, such as a power source, wires, and resistors, in a closed loop. When the circuit is complete, the flow of electric current can power devices connected to the circuit.

3. Why is my circuit not working?

There could be several reasons why a circuit is not working. Some common issues include loose connections, faulty components, or incorrect wiring. It is important to carefully check all the components and connections to troubleshoot and fix the problem.

4. What is the difference between series and parallel circuits?

In a series circuit, the components are connected in a single loop, and the same current flows through each component. In a parallel circuit, the components are connected in multiple branches, and the current is divided between them.

5. How do I calculate the voltage, current, and resistance in a circuit?

Ohm's law states that voltage (V) is equal to current (I) multiplied by resistance (R). So, if you know any two of these values, you can calculate the third using the formula V=IR.

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