DRV10983: Current curve is not sinusoidal

TXH

Part Number: DRV10983
Other Parts Discussed in Thread: DRV10975,

Hello TI experts,

I am trying to using DRV10983EVM to spin my fan in hand. The fan looks rotating well, but the phase current is not so good i think.

I tried to tuning according to the "DRV10983 and DRV10975 Tuning Guide" (SLOU395D), the motor parameter is as below:

OPERATION VOLTAGE	NUMBER OF POLES	MAXIMUM SPEED(RPM)	MAXIMUM CURRENT	R (PHASE-CT)	Kt (PHASEPHASE)	LR CONSTANT	INERTIAL
24V	2	---	0.35mA	1.35OHM	20mV/Hz	26.59mA	200ms

here is the register value:

"DRV10983 0x20 0x49"
"DRV10983 0x21 0x1B"
"DRV10983 0x22 0x2"
"DRV10983 0x23 0x0"
"DRV10983 0x24 0x40"
"DRV10983 0x25 0xFD"
"DRV10983 0x26 0x93"
"DRV10983 0x27 0xB0"
"DRV10983 0x28 0xFF"
"DRV10983 0x29 0xF9"
"DRV10983 0x2A 0xD"
"DRV10983 0x2B 0xC"

the current curve in Tuning Guide should be sinusoidal as below:

How can I tuning the fan to get the good current wave? thanks!

over 1 year ago

0 Vishnu Balaraj over 1 year ago

TI__Mastermind 24405 points

Hi TXH,

Looks like you are working on a trapezoidally wound BLDC motor. Trapezoidal wound BLDC motors generate trapezoidal shaped BEMF voltage so the phase current will also look trapezoidal. Phase current waveform shown in the tuning guide was captured by driving a sinusoidally wound BLDC motor.

Regards,

Vishnu

0 TXH over 1 year ago in reply to Vishnu Balaraj

Prodigy 90 points

OK~ Understood.thanks!

Where can I know more details about the motor control method of DRV10983? FOC? 6-step commutation?

+1 Vishnu Balaraj over 1 year ago in reply to TXH

TI__Mastermind 24405 points

DRV10983 uses 180 deg sinusoidal commutation method. Please refer to the below TIPL video link which has series of BLDC related videos.

training.ti.com/.../1139742

0 TXH over 1 year ago in reply to Vishnu Balaraj

Prodigy 90 points

Hi Vishnu,

If the driving voltage is sinusoidal, why the phase current is trapezoidal? It should be also sinusoidal.

0 Anthony Lodi over 1 year ago in reply to TXH

TI__Mastermind 18450 points

Hi Shawn,

Vishnu will look over this and try to get back to you by the end of the week.

Regards,

Anthony Lodi

+1 Vishnu Balaraj over 1 year ago in reply to TXH

TI__Mastermind 24405 points

TXH,

Shape of the phase current also depends on how the inductor windings are distributed across 360 deg of the stator. Phase current looks trapezoidal because of the charging/discharging pattern of the inductor on the stator coils.

Regards,

Vishnu

0 TXH over 1 year ago in reply to Vishnu Balaraj

Prodigy 90 points

Hi Vishnu,

Thanks a lot. It is clear now for me.

Regards,

Shawn

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DRV10983: Current curve is not sinusoidal