Current Sources & Diode Bridges /w inductive load
Current Sources & Diode Bridges /w inductive load
(OP)
Below is a circuit consisting of a current limiting reactor (L1), and a current transformer (T1) whose outputs are connected to two 3-phase diode bridges (R1 & R1). The bridges are series connected to a RL load.
What is the purpose of the CT? It seems to shift the current 180 degrees (antiphase). How do diode bridges deal with current sources and how does a big reactive load influence the behaviour of the circuit?
What is the purpose of the CT? It seems to shift the current 180 degrees (antiphase). How do diode bridges deal with current sources and how does a big reactive load influence the behaviour of the circuit?






RE: Current Sources & Diode Bridges /w inductive load
The phasing of the CT is not important since the output is rectified, i.e. "dephased".
Gunnar Englund
www.gke.org
RE: Current Sources & Diode Bridges /w inductive load
I simulated this circuit in Matlab Simulink and found a smooth current (ie. very low ripple, due to the big inductance load), but the output voltages of the rectifiers are very erratic.
Do the reactors also act as a voltage source, as they tend to resist changes is current?
RE: Current Sources & Diode Bridges /w inductive load
RE: Current Sources & Diode Bridges /w inductive load
Now, add the main voltage from the rectifier and you get another voltage, about 500 V.
Both these circuits are linear in the RMS sense (but not if you look at instantaneous values - that might be confusing). Being linear, it is legal to superimpose the two and - presto! - you have a voltage from the main circuit that has a droop (reactor impedance times current) plus a smaller voltage that increases when current increases. The result is that the voltage is either relatively constant as load current changes or it may be some other funtion of the load current.
What happens at high currents is dependent on when the CTs saturate. If the cores are designed to saturate at a certian current, you will have a (probably) constant voltage up to that point and then a decreasing voltage. As some kind of a crude current limit function.
Gunnar Englund
www.gke.org
RE: Current Sources & Diode Bridges /w inductive load