Anyone have any info on the ABB ACS 550-01 VSD's please? I am particularly looking for how the motor thermal protection works as I want to model the thermal hot and cold curves in SKM's PTW. Any formulae or thermal curves will be most useful.
Thanks.
Maybe the following illustration will help:
The yellow lagging current flows from the source to the motor regardless of whether there is a capacitor bank or not. The blue leading current flows from the source to the capbank regardless of whether there is a motor or not. The NETT effect is a...
Mate, a capacitor is not a source of steady state power - real or reactive. It can only discharge stored electrical energy back into the system when system volts drop below capbank volts (if it has any). This is very different to a solar panel which is a generator in essence.
I'm a bit puzzled...
My capbank is attached at the same bus as the VFD.
backn4life - Capbank is not a source of electrical power in the greater scheme of things since over one complete cycle the nett influx of electrical energy to the capbank is 0 (neglecting small resistive losses). On a network scale, the capbank...
jghrist
I hear what you say and I fully grasp that analogy, it is synonomous to the belief that a capacitor bank supplies the vars to the local load. This is in reality a misnomer as the capbank is neither a source or sink of electrical energy. In reality the capbank draws leading current from...
For the harmonics gurus,
I have read in quite a few texts on power system harmonics that a VFD is a non-linear load and so is a source of harmonics. Thinking about it I would say that this is misnomer (the way I see it anyway). The VFD is not a source or sink of electrical power. Considering a...
I have worked with 19000/1 CT's for a 660MW generator for protection purposes. But yes, what are the CT's for? If for protection please state what kind of protection.
Ah yes, I see now in PTW that it has a bus scan impedance magnitude vs harmonic order. It assists in flagging potential resonance issues for a given harmonic(s).
I've just done a harmonic study using PTW. This tells me what the V_THDV% and I_THD%, Vrms, Irms are at several locations in the network, the K factor for trfrs, etc. I was thinking, is there a way of predicting if there are potential resonance issues on the network? The network has several LV...
I certainly concur with both statements above provided it is practically possible. In a pure TT system there is no PE from the load to source. However, all loads within an installation should be bonded together, agreed.
I am still yearning for someone to enlighten me as to the answer to my...
If you go down the multiple transformers route, you'd probably want to run them split and not parallel else your fault currents would be substantial, not to mention arc flash headaches! I'd probably look at 4 x 2MVA units. Will mean significantly more hardware and real estate. However, don't...
waross,
Yes, grounded end of the NER is at the source end is what I meant. I get it with regards to the difference in voltage rise (touch voltage) between the solidly earthed case and the NER case.
My question is in relation to the correct designation for the kind of LV earthing system in my...
I know it cannot be TN as
1) the neutral is not solidly earthed and
2) there is no neutral at all
But an IT system as far as I know (could be deadwrong) means neutral is totally insulated from earth or is earthed through a high impedance like we have here. However, T means that the exposed...
I am curious as to what the LV system in the attached drawing would be called. I am aware of TN-C and TN-C-S and TT systems. But what if the supply trfr neutral is high impedance earthed via a 5A neutral earthing resistor as shown in the diagram...
