When a penalty is not involved, the minimal I2R savings will not pay for the installed capacitor bank in your lifetime. The capacitor will likely fail and need replacement before savings are ever achieved.
bandy 2000,
Unless I am crazy, if you look at the impedance from any two phase points into a delta circuit and assume a balanced load (i.e., Z1 = Z2 = Z3 from each delta leg), then the total impedance will be equal to the following assuming we reference 1 & 2:
Z12 equivalent =...
nitro, just one more thing. KW can never be larger than KVA. Again, the fundamental definitions of electrical engineering are still maintained.
KVA = sqrt(KW^2 + KVAR^2)
If you play around with this in a spreadsheet, you will see that KW can never exceed KVA. The best you can get is KW=KVA...
nitro,
Sorry to say but you will have to buy the drink for your co-worker. The laws of electrical engineering do not change just because the fundamental frequency is different. KW is always equal to KVA times power factor. This can get more detailed if we start talking about displacement...
lyledunn,
Your assumption is coorect I believe. If you have a lot of switch mode power supplies, there could be a significant amount of neutral current. This occurs because switch mode power supplies produce a large amount of 3rd harmonic currents. Unfortunately, 3rd harmonic currents are...
ccdubs, it depends.
First of all, if the motor is running and you have a parallel capacitor connected in the circuit to compensate just for the motors power factor, there really is no direct affect on the motor if the power factor is over sized. The motor impedance has not changed and...
GGOSS, I agree personal safety is above all. But remember, almost everything built in this world has a cost/benefit/risk assesment (i.e., bridges and buildings built in an earthquake prone areas, planes, cars etc....).
In any event, we need not argue and I did not try to make it appear so. If...
GGOSS, I did read your email carefully and understand what you are trying to say but again, the method of simply adding a fault contactor on the hot leads has become an industry acceptance and works fine with very little problems. It is a cost/risk benefit and so far the industry is saying the...
GGOSS, we have also been involved with wye-delta softstarters for many years and have used the fault contactor scheme forever. There has never been any magic smoke let out of the box with the thousands of units that are sold in this configuration. Again, I point out the fact that the largest...
jraef, I agree with your concerns that a lot of people are unfamiliar or even understand what is really going on with the inside delta idea. I believe the people that try to do this on their own without help are asking for trouble. However, when our customers contact us with an application...
Marke,
I agree with your phase angle change inside the delta completely. That is why our softstarters are programmed to adjust the phase angle in the algorithm when it is placed inside the delta windings (there is a dip switch on the softstarter to let it know that it is being connected inside...
Jraef, You are correct! The current is reduced to 58% not by 58%. Typo on my part.
In regards to the isolation contactor, the better solution is to use a 'fault' contactor that is installed on the three 'hot' motor leads. With this type of configuration, the fault contactor is designed to...
In regards to Marke's comments, very well explained. To add one additional comment, the current inside the delta is reduced by 58% in relation to the motors rated current. For example, if you have a 100A rated motor, the current inside the delta is 58A. This is why a smaller softstarter can...
Butter,
I suggest you use a softstarter instead. It is smaller, less expensive, and you do not have any transition spikes like open and closed transition W-D starters do. The softstarter is also much more flexible in that it allows you to adjust the reduced voltage settings by simply turning...
