Changing the winding connection mode to modify the motor

When changing the winding connection mode to perform motor modification work, sometimes the speed of the asynchronous motor does not adapt to the mechanical equipment being driven. If there is no suitable speed motor, you can change the number of motor poles to change the speed of the motor to adapt to the needs of mechanical equipment. When the motor is changed to pole, it is generally necessary to change the windings again, to re-determine the number of wires per slot and the wire size, etc., which often results in unnecessary waste. If you take some necessary measures, such as changing the winding wiring, you can achieve the goal of changing the polarity. However, in this way, certain conditions should be met.

1. The requirements for changing the winding connection mode must be met. a. The stator and rotor slots should be compatible with the number of poles. The stator and rotor slots should be compatible with the number of poles. The following relationship must be satisfied: Z is set to -Z to define a ZZ±1 to define a Z to s - the number of rotor slots; P - the number of poles.

When changing the motor speed, the motor speed before and after the change should not be too great. According to the preliminary practice, the use of changing the wiring method to change the pole, increasing the number of poles is more easily realized than reducing the number of poles, and the change in the number of poles is difficult to achieve good results. Usually two poles are changed to four poles, four poles are changed to six poles, six poles are changed to eight poles, etc. It is easier to realize, and it is easy to obtain good results.

c, change the number of poles to consider the relationship between capacity and speed change the number of motor poles, must take into account the motor capacity and speed is approximately proportional to the change. When the motor is changed from a low speed to a high speed, its capacity can be increased, but the capacity of the motor due to the yoke's magnetic flux limitation is not likely to increase in proportion to the rotation speed. When the motor is changed from high speed to low speed, its capacity will be reduced. Due to changes in the cooling conditions of the motor, the reduction in capacity is greater than the reduction in speed. Therefore, when changing the number of motor poles, it is necessary to pay attention to whether the capacity after the pole change is suitable for the mechanical equipment used.

Practice has proved that only when the above three conditions are satisfied, the motor can be reformed, otherwise, even if the number of motor poles is changed. It will also be difficult to achieve the desired number of revolutions.

2. Example of Changing the Winding Connection Mode to Change the Polarity 2.1. Predecessor Technical Data Harbin Guoyuan Public Facilities Co., Ltd. Li Xiaofeng The number of slots Z = 47 slots, the stator core outer diameter D = 493 mm, and the stator core inner diameter D = 327111111. Stator core length L = 260mm. Stator winding technical data: double winding, coil pitch YF11, number of turns of each coil W = 7 inch, wire diameter The number of coils of the original three-phase winding is mx2p = 3x4 = 12 The number of coil groups common to each phase is (mx2p)/m=(3x4)/3=4 The number of common coil groups per branch is (mx2p)/(mxa)=(3x4)/(3x4)=l The number of coils connected in series in each coil is given by Z/(mx2p)=60/(3x4)=5 Number of series windings per phase W1:=Wx5=7x5=35匝2.3 Using original windings by 2P=6 Because the motor stator slot number Zs = 60. The number of rotor slots Z = 47, the number of pole pairs 2p = 6, calculated by: Z set -Z turn = 6047 = 13 (0. ± 1, ± 6,6 ± 1 After analysis, the 4-pole motor can be changed to a 6-pole motor, and the number of slots per phase of a 6-pole motor can be calculated.

Therefore, it is not possible to arrange symmetrical three-phase fractional slot windings, and it is not possible to use the fractional slot winding list distribution method to handle such fractional slots. Generally, the method of vacant partial winding elements is not used. When the number of motor poles is 2P=6, the total number of coils of the three-phase motor windings is mx2p=3x6=18 groups. When the original 2p=4, the number of three-phase windings is 12 groups. Therefore, if the original two coil groups (counting 10 coils) are divided into three coil groups, each three coils are connected into one group. It is not necessary to vacate a coil, so that 12 coils are changed to 18 coils, and 6 coils are left unconnected. Their serial numbers are 10, 20.30, 40, 50, 60, respectively, and they are in symmetrical 6-space locations.

Since the number of coils per phase is 6 groups, the number of branches of the motor can be connected to 4 kinds such as a=l.2.3.6. In the end how much a is chosen is appropriate, this should be considered. If the number of branches is too small (for example, =1), the cross-sectional area of ​​each winding wire is too small, then the current allowed to pass through each phase will be reduced, and the motor capacity will be correspondingly smaller. Reduce. If the branch number a is selected too much (for example, ot=6), the number of winding turns per phase will be too small, which will cause the magnetic densification of each part of the magnetic circuit of the motor to increase, and the no-load current will increase sharply. Large, power factor will drop a lot. Therefore, when selecting the branch number a, the number of turns per phase should be equal to or slightly larger than the number of turns per phase of the original (2P4) as much as possible. Here, a=3 is taken, and each branch has 2 coils. Count 6 sets of coils, the number of windings per phase W: p6x7 = 42 turns.

For the long-distance coil, it can be seen as a Y short-distance coil. The table shows that the short-distance coefficient 1 = 0.988, the effective number of turns per phase winding Ki! > Change the current before each pole to 137/4=34.25A. If the current density after changing the pole is the same as before changing the pole current, the current allowed through each branch is still 3425A. The winding current per phase is 34.25x3. = 102.75A, is the original current 102.75/137 = 0.74 times. Because the output power of the motor is proportional to the magnitude of the current, the output power pte of the motor is accordingly reduced by 0.74 times the Pd before the pole change, that is: p=0.74xpel=75x0.74=55kWo After the above analysis and demonstration. Change the winding connection to change the motor. It is an effective method that can meet the requirements of the load on the speed and motor output power, lifting the efficiency of the use of the motor.