_O & M MANUAL - WEST LANE MOBILE HOME PARK

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THREE PHASE POWER UNBALANCE A full three phase supply consisting of three individual transformers or one three phase transformer is recom- mended. "Open" delta or wye connections using only two transformers can be used, but are more likely to cause poor performance, overload tripping or early mo- tor failure due to current unbalance. Check the current in each of the three motor leads and calculate the current unbalance as explained below. If the current unbalance is 2% or less, leave the leads as connected. If the current unbalance is more than 2%, current read- ings should be checked on each leg using each of the three possible hook-ups. Roll the motor leads across the starter in the same direction to prevent motor reversal. To calculate percent of current unbalance: A. Add the three line amp values together. i--� Example: T3 -R = 51 amps T1 -B = 46 amps T2 -W = 53 amps Total = 150 amps =3=50 amps — 46 = 4 amps 4=50=.08or 8% INSULATION RESISTANCE READINGS B. Divide the sum by three, yielding average current. C. Pick the amp value which is furthest from the average current (either high or low). D. Determine the difference between this amp value (furthest from average) and the average. E. Divide the difference by the average. Multiply the result by 100 to determine percent of unbalance. Current unbalance should not exceed 5% at service factor load or 10% at rated input load. If the unbalance cannot be corrected by rolling leads, the source of the unbalance must be located and corrected. If, on the three possible hookups, the leg farthest from the average stays on the same power lead, most of the unbalance is coming from the power source. Contact your local power company to resolve the imbal- ance. Hookup 2 Hookup 3 L1 L2 L3 L1 L2 L3 1 1 1 1 1 1 T T T T T T W R B B W R T2 T3 T1 T1 T2 T3 T2 -W = 50 amps T3 -R = 48 amps T1-13 = damps Total = 150 amps =3=50 amps —48=tamps 2 _ 50 = .04 or 4% Normal Ohm and Megohm Values between all leads and ground T1 -13 = 50 amps T2 -W = 49 amps T3 -R = 51 amps Total = 150 amps 3 = 50 amps —49=1amps 1=50=.02or 2% Condition of Motor and Leads Ohm Value Megohm A new motor (without drop cable). 20,000,000 (or more) 20 (or more) A used motor which can be reinstalled in well. 10,000,000 (or more) 10 (or more) New motor. 2,000,000 (or more) 2 (or more) Motor in good condition. 500,000 - 2,000,000 .5-2 Insulation damage, locate and repair. Less than 500,000 Less than .5 Insulation resistance varies very little with rating. Motors of all HP, voltage and phase ratings have similar values of insulation resistance. Insulation resistance values above are based on readings taken with a megohmmeter with a 500V DC output. Readings may vary using a lower voltage ohmmeter, consult factory if readings are in question. 7 Hookup 1 Starter Terminals L1 L2 L3 1 1 1 T T T Motor Leads R B W T3 T1 T2 i--� Example: T3 -R = 51 amps T1 -B = 46 amps T2 -W = 53 amps Total = 150 amps =3=50 amps — 46 = 4 amps 4=50=.08or 8% INSULATION RESISTANCE READINGS B. Divide the sum by three, yielding average current. C. Pick the amp value which is furthest from the average current (either high or low). D. Determine the difference between this amp value (furthest from average) and the average. E. Divide the difference by the average. Multiply the result by 100 to determine percent of unbalance. Current unbalance should not exceed 5% at service factor load or 10% at rated input load. If the unbalance cannot be corrected by rolling leads, the source of the unbalance must be located and corrected. If, on the three possible hookups, the leg farthest from the average stays on the same power lead, most of the unbalance is coming from the power source. Contact your local power company to resolve the imbal- ance. Hookup 2 Hookup 3 L1 L2 L3 L1 L2 L3 1 1 1 1 1 1 T T T T T T W R B B W R T2 T3 T1 T1 T2 T3 T2 -W = 50 amps T3 -R = 48 amps T1-13 = damps Total = 150 amps =3=50 amps —48=tamps 2 _ 50 = .04 or 4% Normal Ohm and Megohm Values between all leads and ground T1 -13 = 50 amps T2 -W = 49 amps T3 -R = 51 amps Total = 150 amps 3 = 50 amps —49=1amps 1=50=.02or 2% Condition of Motor and Leads Ohm Value Megohm A new motor (without drop cable). 20,000,000 (or more) 20 (or more) A used motor which can be reinstalled in well. 10,000,000 (or more) 10 (or more) New motor. 2,000,000 (or more) 2 (or more) Motor in good condition. 500,000 - 2,000,000 .5-2 Insulation damage, locate and repair. Less than 500,000 Less than .5 Insulation resistance varies very little with rating. Motors of all HP, voltage and phase ratings have similar values of insulation resistance. Insulation resistance values above are based on readings taken with a megohmmeter with a 500V DC output. Readings may vary using a lower voltage ohmmeter, consult factory if readings are in question. 7