3-Phase BLDC Motor Control with Sensorless Back EMF ... - Freescale

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Target Motor Theory Figure 3-5. Power Stage - Motor Topology The second goal of the model is to find how the motor characteristics depend on the switching angle. The switching angle is the angular difference between a real switching event and an ideal one (at the point where the phase to phase Back-EMF crosses zero). The motor-drive model consists of a normal three phase power stage plus a Brushless DC motor. The power for the system is provided by a voltage source (U d). Six semiconductor switches (S A/B/C t/b), controlled elsewhere, allow the rectangular voltage waveforms (see Figure 3-2) to be applied. The semiconductor switches and diodes are simulated as ideal devices. The natural voltage level of the whole model is put at one half of the DC bus voltage. This simplifies the mathematical expressions. 3-Phase BLDC Motor Control, Rev. 1 8 Freescale Semiconductor Preliminary
3.4.1 Mathematical Model The following set of equations is valid for the presented topology: where: u VA …u VC u A …u C u A u B u C u O ⎛ C ⎞ 1 = --⎜2u 3 VA – uVB – uVC + ⎟ ⎜ ∑ uix⎟ ⎝ ⎠ 3-Phase BLDC Motor Control, Rev. 1 Power Stage - Motor System Model Freescale Semiconductor 9 Preliminary x = A ⎛ ⎞ 1 = --⎜2u 3 VB – uVC – uVA + ∑ u ⎟ ⎜ ix⎟ ⎝ ⎠ C x = A ⎛ ⎞ 1 = --⎜2u 3⎜ VC – uVA – uVB + ∑ u ⎟ ix⎟ ⎝ ⎠ C ⎛ ⎞ 1 = --⎜ u 3⎜ ∑ Vx – ∑ u ⎟ ix⎟ ⎝ ⎠ x = A 0 = iA + iB + iC C x = A C x = A are “branch” voltages; the voltages between one power stage output and its virtual zero. are motor phase winding voltages. (EQ 3-1.) uiA…uiC are phase Back-EMF voltages induced in the stator winding. uO is the voltage between the central point of the star of motor winding and the power stage natural i A …i C zero are phase currents The equations (EQ 3-1.) can be written taking into account the motor phase resistance and the inductance. The mutual inductance between the two motor phase windings can be neglected because it is very small and has no significant effect for our abstraction level. where: uVA – uiA uVB – uiB uVC – uiC C ⎛ ⎞ 1 --⎜ u 3 ∑ Vx – ∑ u ⎟ diA – ⎜ ix = R⋅i ⎟ A + L dt ⎝ ⎠ x = A C C x = A ⎛ ⎞ 1 --⎜ u 3 ∑ Vx – ∑ u ⎟ diB – ⎜ ix = R⋅i ⎟ B + L dt ⎝ ⎠ x = A C C x = A ⎛ ⎞ 1 --⎜ u 3 ∑ Vx – ∑ u ⎟ diC – ⎜ ix = R⋅i ⎟ C + L dt ⎝ ⎠ x = A R,L - motor phase resistance, inductance C x = A (EQ 3-2.)
Page 1 and 2: Freescale Semiconductor Application
Page 3 and 4: Table 2-1. Memory Configuration 56F
Page 5 and 6: Stator Stator winding (in slots) Sh
Page 7: 3.3 Why Sensorless Control? 3-Phase
Page 11 and 12: 3.6 Back-EMF Sensing Circuit 0 30 6
Page 13 and 14: • Running on one of three optiona
Page 15 and 16: Power line PC Master START STOP UP
Page 17 and 18: PWM1 S At PWM2 S Ab PWM3 S Bt PWM4
Page 19 and 20: 3-Phase BLDC Motor Control, Rev. 1
Page 23 and 24: 5.4.2.2 Running - Commutation Times
Page 27 and 28: Phase Back-EMFs Back-EMF Zero Cross
Page 31 and 32: 6.3 Low Voltage Hardware Set The sy
Page 33 and 34: 7. SW Design 3-Phase BLDC Motor Con
Page 35 and 36: Interrupt Up Button Up Button ISR:
Page 37 and 38: Protection processes are shown in F
Page 39 and 40: 7.3.1 Main SW States - General Over
Page 41 and 42: • Starting (Back-EMF Acquisition)
Page 43 and 44: 7.3.4.3 Commutation Control - Set R
Page 45 and 46: 7.3.6 State Diagram - Process Curre
Page 49 and 50: 11. Setting of SW parameters for ot
Page 51 and 52: 11.2.2 Start-up Periods The constan
Page 53 and 54: Coef_CmtPrecompLShft Coef_CmtPrecom

3-Phase BLDC Motor Control with Sensorless Back EMF ... - Freescale

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