Recent content by Guineafowl

Ok, there must be some rule I’m missing, after which the penny will drop. Forgive my stupidity. How is the X1 (or U) junction defined? Put another way, if you had a delta-connected transformer side open in front of you, which one is the first winding, and which is the X1 or U connection? In...

So, what would lead you to point the X1 vector at the dot or non-dot end? It seems arbitrary.

Thanks, so by that definition the group 1 will be a 30°, and the group 11 a 330°? There were two other examples: I make these group 7 and 11 respectively, so I were all four examples wrong? The only other point is, for the two examples above, the vector X1 is pointing at the non-dot end of...

On behalf of someone on another forum; In both cases, he’s been given the answer, but doesn’t understand it: To me, the group does make sense in both cases, if you imagine the diagrams rotating anticlockwise: the vector X1 lags by 30° in the first case, giving 11 o’clock as the group, and...

Results: Capacitance (uF):Current U:Current V:Current W: 013.413.18.3 1212.812.68.0 209.410.07.2 359.310.57.0 It looks like a low point around the 20 uF mark. At this level, subjectively, the motor sounds happier and gets less hot. Phase balance looks better, too. Increasing to 35...

Ok, well I have 30 uF and 20 uF coming, so that will give me the range 12-50 uF. Checking for motor voltage spikes, I assume my Fluke 87V on peak detect should spot them?

An interesting short article on self-excitation in pf-corrected induction motors: https://nepsi.com/resource/Self-Excitation Concerns.pdf The key point is, if the capacitive reactance is greater than the motor magnetising reactance, as when the cap is deliberately under-sized, the resonant...

I’ve had the motor apart for testing the windings and changing the bearings: It’s dual voltage, ie 230V delta or 400V star. Latter configuration currently. No internal switch.

As soon as power is cut, the motor stops dead from the friction. Does that allay any fears? I’d guess that, at switch-off, we’ll be left with three LC tanks, complicated by the rotor nearby. Would they just ring down to nothing? The motor being fairly modern and dual voltage/frequency, I...

I’ve ordered three ##450V, 30\mu F## capacitors, having approached the calculation differently and got the same answer: At ##400V, 11A, 50Hz, cos\phi=0.65, \phi=49.5°##: ##|S| = \sqrt 3 VI = 7.62 kVA## ##P = |S|cos\phi = 4.95 kW## ##Q = Ptan\phi = 5.80 kVAR## The above with a ##cos\phi## of...

Thanks, I’ll get some EP grease. The only problem is, the lubricator is an oil reservoir, 11, and a tight-fitting felt wick, 9, which might just clean away the grease as it goes. I wonder if I could mix up some EP with the normal oil and try that? The phosphor bronze lift nuts, acting on the...

The screw is on the right, and turns the other screw via two 90deg gearboxes and a driveshaft under the lift area. The lift nut is no. 19 and it lifts the squarish bracket (12), which in turn lifts the carriage with the arms that contact the car (not shown). Above all that is the autolubricator...

Ok, so a cosphi of 0.65 gives an angle of 49.5 degrees: $$Z=36.4\Omega <49.5° = 23.6 +j27.7\Omega$$ $$C=\frac 1 {2\pi f 27.7} = 115 \mu F$$

VFD manual should be linked in the first post. Yes, I thought lifting the car slower might reduce the loading of the system. Or, running at 60Hz might improve the power factor, according to the motor plate. All doable with a twiddle of a pot. It seems very inefficient. Lifting a 2-tonne car at...

As a first attempt, looking at the motor plate (connected in star): $$Z=\frac V I = \frac {400} {11} = 36.4\Omega$$ Find capacitor with Xc of that value at 50Hz: $$ C = \frac 1 {2\pi f X_c} = 87\mu F$$