Motorola M68HC08 manual Power Stage Motor Topology

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

BLDC Motor Control

Id0

+

ud/2	=	SAt	SBt				SCt
	-
ud/2	+
	=	SAb	ISa SBb			ISb SCb		ISc
	-
		uVA	uAB				uBC
			uVB				uVC
							uCA
						B
					uSb	uRb
						uLb
			u0
						ubackEMF b
			uSa			O	u
							backEMF c
			u	uLaubackEMF a			uLc u
			A	Ra			uSc	Rc
								C

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-phaseback-EMF crosses zero).

The motor-drive model consists of a normal 3-phase power stage plus a brushless dc motor. Power for the system is provided by a voltage source (Ud). Six semiconductor switches (SA/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.

Designer Reference Manual		DRM028 — Rev 0
28	BLDC Motor Control	MOTOROLA
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