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Typically single phase motors go up to 10hp. Wouldn't be very efficient at about 100 amps. A 20hp 3 phase motor at 230v pulls 52 amps. The 10hp single phase 230v pulls 50 amps.
Measure the current on the incoming side of the starter.
depending on 1phase or 3phase voltage motor , the amphere requirement is found outfor 3phase AC motor use this formula: (HP x 746)/(1.73 x E x Eff x PF)for 1phase AC motor : (HP x 746) / (E x Eff x PF)
THE FIRST THING IS TAKE THE READING OFF LOAD AND SEE IF THEY ARE BALANCED. HAS THE MOTOR BEEN RECENTLY REWOUND? GET A MOTOR REPAIR COMPANY TO LOOK AT THE MOTOR AND SEE IF IT HAS BEEN WOUND CORRECTLY. IF THE STAR-DELTA WORKS CORRECTLY IT SHOULD START IN STAR FOR ABOUT FIVE TO TEN SECONDS AND GO INTO DELTA THIS IS DEPENDANT ON THE STARTING CURRENT THE MANUFACTURE OF THE SWITCH AND THE APPLICATION. CHECK ALL THREE PHASES ARE BALANCED AND IF THEY ARE THE MOTOR WINDINGS MAY NOT BE CORRECTLY WOUND. SOME HAVE STAR CONNECTIONS BUILT IN.LOOKING AT THE AMPERAGE THE LOAD REQUIREMENT IS ONLY A FRACTION OF WHAT YOU ARE GETTING SO IT LEAVES ONLY TWO THINGS I......MOTOR FAULT 2.....WHAT EVER THE MOTOR IS DRIVING IS PUTTING A MASSIVE PRESSURE ON THE MOTOR CAUSING IT TO OVERLOAD.
To size cable the amperage must be known. Use the following equation to find amperage. Amps = kW x 1000/1.73 x volts x pf. A standard motor's power factor between 10 to 100 HP is .86 to .92. Amps = 90 x 1000 = 90000/ 1.73 x 440 x .92 = 90000/700 = 128 amps. Motor feeders have to be rated at 125% of the motor full load amperage. 128 x 125% = 160 amps. A 2/0 copper conductor with an insulation factor of 75 or 90 degrees C is rated at 175 and 185 amps respectively.
Typically single phase motors go up to 10hp. Wouldn't be very efficient at about 100 amps. A 20hp 3 phase motor at 230v pulls 52 amps. The 10hp single phase 230v pulls 50 amps.
Measure the current on the incoming side of the starter.
40 amps
depending on 1phase or 3phase voltage motor , the amphere requirement is found outfor 3phase AC motor use this formula: (HP x 746)/(1.73 x E x Eff x PF)for 1phase AC motor : (HP x 746) / (E x Eff x PF)
160 Amp. MCCB 45 KW Contactor (67.5-112.5) Thermal Over Load
It depends on the voltage: 208 v 14 amps, 415 v 7 amps, 480 v 6 amps.
If the total bank is 750kVA, full load amps is 902A.
Since watts = volts times amps times 1.73 times power factor (for a three phase motor): W = E * I * 1.73 * PF Solving for I: I = W / (E * 1.73 * PF) Lets say your motor has a PF of 0.85: I = 10000 / (415 * 1.73 * 0.85) I = 16.39A If this is for your homework (I hope not) and PF is not given, then you will substitute 1.0 for the PF and, of course, arrive at a different answer!
Pls.answer me of above question
First and foremost is the information the manufacturer puts on the nameplate of the motor. Second, the generic amperage can be found on motor charts that are on the Internet. Third you can use a formula to find the approximate amperage. HP = Amps x Volts x 1.73 x pf/746. Transposed for Amperage, Amps = HP x 746/Volts x 1.73 x pf. Use pf = .9 Amps = 10 x 746/ 208 x 1.73 x .9 = 7460/323.85 = 23.03 amps. See how much easier it is to read the nameplate.
The only thing that will trip the starter, is the load of the motor. Check the motor leads to make sure you have not crossed them over coming from the motor junction box. If the motor current is normal nameplate full load amps when run across the line then reduce the timing of the timer on the switch over from star to delta.
THE FIRST THING IS TAKE THE READING OFF LOAD AND SEE IF THEY ARE BALANCED. HAS THE MOTOR BEEN RECENTLY REWOUND? GET A MOTOR REPAIR COMPANY TO LOOK AT THE MOTOR AND SEE IF IT HAS BEEN WOUND CORRECTLY. IF THE STAR-DELTA WORKS CORRECTLY IT SHOULD START IN STAR FOR ABOUT FIVE TO TEN SECONDS AND GO INTO DELTA THIS IS DEPENDANT ON THE STARTING CURRENT THE MANUFACTURE OF THE SWITCH AND THE APPLICATION. CHECK ALL THREE PHASES ARE BALANCED AND IF THEY ARE THE MOTOR WINDINGS MAY NOT BE CORRECTLY WOUND. SOME HAVE STAR CONNECTIONS BUILT IN.LOOKING AT THE AMPERAGE THE LOAD REQUIREMENT IS ONLY A FRACTION OF WHAT YOU ARE GETTING SO IT LEAVES ONLY TWO THINGS I......MOTOR FAULT 2.....WHAT EVER THE MOTOR IS DRIVING IS PUTTING A MASSIVE PRESSURE ON THE MOTOR CAUSING IT TO OVERLOAD.