why we use star connection in HT motor? and delta connection
in LT motor
Answer Posted / madhu
The starting current for motors is 6 to 7 times full load current. So start-up power will be large if HT motors are delta connected. It may cause instability (voltage dip) in case small Power system. In starred HT motor starting current will be less compared to delta connected motor. So starting power is reduced. Starting torque will also be reduced. (It will not be a problem as motors are of high capacity.)
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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?
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