This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • Resolved

[FAQ] Selecting Integrated FET/control BLDC Motor drivers based on Motor Datasheet

Mastermind 45130 points

Replies: 1

Views: 237

Understanding the parameters of a motor is very important in selecting a motor driver as the rating of the FETs and control method of the Motor driver depends on motor parameters and construction. A motor has electrical and mechanical parameters listed in the datasheet as it is an electro-mechanical machine that converts electrical energy to mechanical energy.

Electrical circuit model of a Brushless DC (BLDC) Motor showing electrical and mechanical parameters is shown in Figure 1.

Figure 1. Electrical Circuit Model of BLDC Motor

The following table lists and explains the electrical and mechanical parameters of a BLDC motor.

Electrical Parameter

Typical Symbol

Unit

Definition

Rated voltage

Vm

Volts

Rated voltage that is applied to the motor phases.

Rated current

i

Ampere

Current drawn by the motor when the motor is loaded at rated torque.

No load current

inl

Ampere

Current drawn by the motor when there is no load on the motor shaft.

Peak current/stall current

ipk

Ampere

Current drawn by the motor when the motor shaft gets locked.

Back EMF constant

Kt

v/Hz or v/rpm or v/rad/sec

Induced voltage Vt on stator windings at 1 Hz or 1 rpm or 1 rad/sec.

Stator/Winding resistance

R

Resistance across two phases of the motor.

Stator/Winding inductance

L

H

Inductance across two phases of the motor.

Mechanical Parameter

Typical Symbol

Unit

Definition

Rated Speed

Hz or rpm or rad/sec

Rated speed of the motor.

Rated Torque

Tm

Nm

Torque generated by the motor at rated speed.

Stall Torque

Ts

Nm

Maximum load torque at which the rotor gets locked.

Rotor inertia

J

Oz-in-s2/N-m-s2

Rotor moment of inertia. This is useful to determine the acceleration and deceleration rates, the dynamic response of the system and to calculate the mechanical time constant of the rotor.

Table 1. Electrical and Mechanical parameters of a BLDC motor.

How to select a BLDC motor driver based on the information available in Motor Datasheet?

Determining voltage and current rating of the integrated FETs based on the motor voltage and current rating is the first step in selecting a Motor driver.

Below are the parameters in the motor datasheet that should be considered when selecting a Motor driver with integrated FET architecture.

  • Rated Voltage Vm
  • Peak current ipk

Power supply voltage Vs (Abs max) and peak output current is of the integrated FET device (listed in table 2) should be compared with rated voltage Vm and peak current ipk of the motor. Vs and is should be slightly greater than Vm and ipk.

Below are the parameters in the motor datasheet that should be considered while selecting a Motor driver with integrated control architecture.

  • Rated Voltage Vm
  • Peak current ipk
  • Rated current i
  • Back EMF Constant Kt
  • Stator resistance R
  • Stator inductance L

Similar to integrated FET devices, Vs and is of integrated control devices should be slightly higher than Vm and ipk. Motor parameters such as R, L and Kt are used in the motor control algorithm of integrated control devices. R, L and Kt in the motor datasheet should be within the applicable range of R, L and Kt (listed in table 2) that the integrated control device can support.

 

Device

Architecture

Power Supply voltage Vs

Peak Current is

Motor phase-phase resistance

Motor phase-phase inductance (mH)

BEMF Constant Kt (mV/Hz)

Abs Max

Abs Max

Min

Max

Min

Max

Min

Max

DRV8313

Integrated FET

65

3

N/A

N/A

N/A

DRV8312

Integrated FET

70

6.5

DRV8332

Integrated FET

70

13

DRV10964

Integrated Control

5.5

0.875

5

20

0.05

1

1

100

DRV10970

Integrated Control

18

1.5

N/A

N/A

N/A

N/A

N/A

N/A

DRV10974

Integrated Control

20

2.5

2

40

0.07

 

5

150

DRV10975

Integrated Control

18

2

0.6

24

0.07

 

1

1800

DRV10983

Integrated Control

28

3

0.6

38

0.07

 

1

1800

DRV10983-Q1

Integrated Control

28

3

0.6

38

0.07

 

1

1800

DRV10987

Integrated Control

28

3

0.6

38

0.07

 

1

1800

Table 2. Integrated FET and Integrated Control device parameters.

For more details, please refer to the Brushless-DC Motor Driver Considerations and Selection Guide.

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.