I am trying to understand if Underexcitation limiter (UEL) is functional if the voltage regulator is set to manual mode when connected to a large system. By functional, I mean if the UEL will enforce the excitation limit when in manual mode. My understanding is that if the Automatic Voltage...
How does one set the stopped state cooling time of an induction motor without the datasheet providing that value? In some digital relays, there is a running cooling time (or rather running time constant entry), and also a separate entry for stopped cooling time. Since the shaft-connected fan or...
I understand that the Service Factor of the motor is the multiplier above the nameplate HP up to which the motor is rated for a continuous running capability -- my question is, technically how is this continuous capability limit defined and what exactly changes when the motor exceeds nameplate...
Hi dpc, thanks for your reply; my understanding is also the same regarding the net flux on the core. So would you also say that the X axis (H component) of a typical BH characteristic curve is referring to the magnetizing current component only (assuming length and turns are constant), i.e...
In the BH curve - H (the magnetic field strength) is in ampere turns per meter. If I keep the magnetic path length constant, H can be varied by varying the current. However, I want to make sure I understand this correctly - is current on the X axis of the BH curve referring only to the...
Okay, thank you, that clears the primary voltage part, but what I was getting at was if you are saying that the transformer 'does' saturate for increasing current (based on my question) because of non-ideal conditions, my question is this:
1. Shouldn't the primary voltage increase to a high...
Gunnar, is that B-H curve test done on a transformer with secondary open and by applying increasing voltage from the primary to increase the current? If so, would the self-induced Primary voltage be close to the supply voltage before saturation, but collapse after saturation? -- And just to...
Gunnar, looking at the B-H curve you posted, I can see that an increase in current (H) causes some saturation (flat B), but I'm still wondering how the transformer behavior would allow this? Because an increase in secondary current should increase the primary current; The additional fluxes...
My understanding is that at no load, a transformer does have a certain no-load flux in the core, due to the magnetizing current in the branch. When it is loaded, the secondary draws more current, create an opposing flux (Lenz's law) that opposes the primary flux - and this inturn reduces the...
Why is this an issue with Cross-compound units specifically, since I didn't see the recommendation of grounding only one unit in other type of parallel generating units?
First, as per the attached picture in the link, a cross-compound unit with two generators is shown, and one is shown to rotate at 3600 rpm, while the other is at 1800 rpm.
1. Does the number of poles vary in each generator so as to produce the same frequency?
2. Why is it recommended (from...
Thanks Jraef and Waross!
1. Jraef, let me see if I understand this: In the hypothetical scenario, you are saying the rated MECHANICAL kW output is not going to be the rated output, but the current could possibly be 111% of rated amps if the voltage goes to 90% though. If my understanding is...
Is an Induction motor considered to be operating at Service Factor 1.0 if it is operating at rated kW output but at 90% rated voltage with 111% of the rated full-load current?
In page 2 in the second paragraph from the link, the author discusses this, but I am not clear as to what the author...
