# The Electronic Switch of Windings of a Standard BLDC Motor
## 3 Experimental Verification and Results  
Winding connection options 1-3 are connected according to the Star scheme, and winding connection options 4-6 are connected according to the Delta scheme; for details see Figure 6. All measurements were made at a constant supply voltage of +24 Volts. The results are summarized in Table 1.  
The main results confirmed that the Star windings connection scheme and the switching scheme inside the phase with its maximal resistance reaches its optimal performance for the low speed (high traction loads). In contrast, the Delta circuit and the switching circuit inside the phase with its minimal resistance are more efficient under the high speed conditions. The performances labeled by scheme numbers from Table 1 are further depicted in Figure 11. The progressions show that each connection option of the stator windings has its optimal range of operating speeds, which is indicated with a bar chart at the bottom of the graph. The color indicates an optimal winding scheme selected. The progressions fully confirm the theoretical justification and confirm that the electronic switch did not affect the performance itself but enabled dynamic winding switching capability even under the operation without any negative effect on the performance. With respect to results shown in Figure 11, to obtain stable operation and high torque on the shaft no matter the operational conditions and demands, it is recommended to connect the windings according to option No. 1 for the stable low speed conditions and high torque. Unlikely, to obtain maximum speed with an optimal performance it is recommended to set the connection scheme according to the option No. 6. The \"dip\" is clearly visible on the operating current progression for options No. 3 and No. 6. This is due to the small values of the winding impedance of the motor developed for the testing. This disadvantage can be further eliminated at the stage of calculating the characteristics of a BLDC motor designed to work with a winding switch. Figure 10: The experimental set-up. Figure 9: The realization of the electronic switch. Since the speed of the BLDC motor is directly related to the KV coefficient, it is clear that when switching windings within different schemes, the KV coefficient also changes. The KV coefficient has a direct effect on the reliability of rotation synchronization when controlling back electro-magnetic force (BEMF) signals. When switched schemes 1 and 2 are compared under the same conditions, i.e., at the same speed of 100 RPM, the current consumption is almost the same, but scheme No.1 has a KV coefficient doubled with respect to scheme No.2, and thus the BEMF based synchronization will be more reliable. This aspect confirms original expectations that the winding switching, when optimal schemes per specific operational conditions are considered, increases the reliability of rotation synchronization of BLDC motors. Another aspect of the switching is thermal losses in the windings, which are also optimized. If schemes No.1 and No.6 are compared under the same conditions, i.e., at the same speed of 300 RPM, the current consumption differs 3.5 times (42 mA and 154 mA respectively). An excess current is converted into heat losses. This confirms the well-known conclusion that motors with high winding impedance are preferable for low-speed operation, since such motors are not capable of reaching high speeds. The proposed winding switch eliminates this disadvantage and allows to combine economy at low speeds and performance at high speeds with reduced heat loss.