The load current of the motor with no load current, and power relations

Asynchronous motor no-load running, set the current in the three-phase winding, referred to as the no-load current. Most of the no-load current is used to produce a rotating magnetic field, known as the no-load excitation current, no-load current reactive component. There is a small part of no-load current is used to produce all kinds of power loss during no-load running (such as friction, ventilation and core loss), the no-load current is a part of the active component, due to account for the proportion of small, negligible. Therefore, can think of is reactive current idle current. From this point of view, it is as small as possible, so that www.facebook.com/dongfeng.motor the power factor of the motor raised, the power supply is good. If no load current is big, because of the stator winding conductors carrying area is certain, allowed through current is certain, allows for active current can reduce flows through a wire, the motor can drive the load will be reduced, the motor output is reduced, with too much load, winding would be easy to fever. 

But the no-load current also cannot too small, otherwise will affect the other performance of the motor. Generally the no-load current of the small motor is about 30% ~ 70% of rated current, ac synchronous motor the no-load current of the large and medium-sized motor is about 20% ~ 40% of rated current. What is specific to the no-load current of magnet generator an electric motor, the motor nameplate or product manuals, generally not marked. Have electrician often need to know how much is this value, this value to judge the quality of the motor repair, can use. (2) formula is the scene quickly calculate motor no-load current of specific numerical formula, it is a lot of test data. It is in line with "the no-load current of the motor is the 1/3 of its rated current". At the same time it is in line with practice experience: "the no-load current of the motor, shall not exceed the capacity of the kw number can be used for" the principle of (after repair of old, small capacity motor). Formula "capacity by about eighty percent for" refers to the general motor no-load current value is about 0.8 times the number of nominal capacity kw motor. No-load current of medium-sized, 4 or 6 pole motor, is the number of motor capacity kw 0.8 times; New series, large capacity, small number of level 2 of the motor, the no-load current calculation according to the number of "xinda sixty percent less"; To the old, old series, smaller volume, the number of large more than 8 pole motor, the no-load current, calculated on "is a small number of very many kilowatts", namely the no-load current value kw number approximately equal capacity, but is generally less than kilowatts.