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advantages of vvvf drives over non vvvf drives for EOT cranes
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Answer Posted / lokesh kumar soni
smooth start and stop.
no jerking of load.
exact positioning
better protection for motor.
high/low speed selection.
reliability of break shoe.
programmable break control.
easy circutry
reduction in controls
increases motor life
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11 kg trivevter meter has rating of -/5amps. And pt ratio11000/110v and is connected with 11kv ct/pt unit of cr ratio 75/5amps. And pt ratio of 11000/110v while checking accuracy of meter with HT Accuchek meter what value of PT ratio and CT ratio to be filled in Accuchek meter
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1. A 380 / 220 V r.m.s. 3-phase 4-wire circuit carries loads of 8 + j8.1 ohm; 4 + j4.1 ohm; and 2 +j2.1 ohmin the three phases respectively. The length of the circuit is 100 m, and the resistivity of the phase conductors is 0.0005 Ω/m. The neutral conductor is of the same size as the phase conductors. a) Select a reference angle 0for the first phase. Then write down the three phase voltages in both polar format and complex number format. b) Make appropriate assumptions, and take temperature effects on resistance is insignificant. Calculate the currents in the three phases. (Note: Determine conductor resistance, and apply Kirchhoff’s Voltage Law) Based on the result, suggest a main switch rating for the circuit. c) Show your preferred direction of neutral current in a diagram, and then determine its value. (Note: Apply superposition principle, and Kirchhoff’s Current Law) Use its magnitude to show that in this circuit, the unbalanced load may increase the voltage drop in some of the phases. (Note: Also observe the common volt drip in neutral) State your assumptions, if there are any. d) Suddenly the neutral wire of the circuit is broken. Estimate the new currents in the first phase, i.e. Phase L1. State your assumptions, if there are any.
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Dear all, I just want to ask an expert on this forum for some insights. For the magnetic balance test, when applied voltage on a Delta-Star transformer e.g. Dyn11, the following relationships apply for HV side: 1. H1-H2 = H2-H3 H3-H1 2. H2-H3 = H3-H1 H1-H2 3. H3-H1 = H1-H2 H2-H3 For the LV side also: 4. X1-X0 = X2-X0 X3-X0 5. X2-X0 = X3-X0 X1-X0 6. X3-X0 = X1-X0 X2-X0 Is there a similar pattern for Y-d, Y-Y, D-d? And how about Y-z, D-z, Z-y transformers? I've tested a YNzn5 transformer and for LV side I don't see the pattern. In this particular case I got for LV side the following (see values below): H1-H0 H2-H0 H3-H0 X0-X1 X0-X2 X0-X3 128.0 119.9 7.2 29.2 13.3 15.8 70.7 128.4 59.2 23.4 22.0 3.6 7.2 120.1 128.1 13.4 29.3 15.8 What is the relationship here for LV? For row 1 I see the relationship, for row 3 I also see but it's shifted, but for row 2 I don't see such relationship. Any suggestions, answers, someone?
What is the Difference between Ac Drives and Dc Drives? According to application, speed, Torque, cost, Reliability, Construction, Motor etc... Thankyou !!!
howmany electrician should maintain for a 1000 kva used plant... in kerala..
