5.8 Tuning an axis for velocity control

Drives designed for velocity control incorporate their own velocity feedback term to provide system damping. For this reason, KDERIV (and KVEL) can be set to zero.

Correct setting of the velocity feed forward gain KVELFF is important to get the optimum response from the system. The velocity feed forward term takes the instantaneous velocity demand from the profile generator and adds this to the output block (see Figure 16). KVELFF is outside the closed loop and therefore does not have an effect on system stability. This means that the term can be increased to maximum without causing the motor to oscillate, provided that other terms are setup correctly.

When setup correctly, KVELFF will cause the motor to move at the speed demanded by the profile generator. This is true without the other terms in the closed loop doing anything except compensating for small errors in the position of the motor. This gives faster response to changes in demand speed, with reduced following error.

5.8.1 Calculating KVELFF

To calculate the correct value for KVELFF, you will need to know:

HThe speed, in revolutions per minute, produced by the motor when a maximum demand (+10V) is applied to the drive.

HThe setting for LOOPTIME. The factory preset setting is 1ms.

HThe number of encoder lines for the attached motor. Baldor BSM motors use either 1000 or 2500 line encoders.

The servo loop formula uses speed values expressed in quadrature counts per servo loop. To calculate this figure:

1.First, divide the speed of the motor, in revolutions per minute, by 60 to give the number of revolutions per second. For example, if the motor speed is 3000rpm when a maximum demand (+10V) is applied to the drive:

Revolutions per second

=

3000 / 60

=50

2.Next, calculate how many revolutions will occur during one servo loop. The factory preset servo loop time is 1ms (0.001 seconds), so:

Revolutions per servo loop

=

50 x 0.001 seconds

=0.05

3.Now calculate how many quadrature encoder counts there are per revolution. The NextMove BXII counts both edges of both pulse trains (CHA and CHB) coming from the encoder, so for every encoder line there are 4 ‘quadrature counts’. With a 1000 line encoder:

Quadrature counts per revolution

=

1000 x 4

=4000

4.Finally, calculate how many quadrature counts there are per servo loop:

Quadrature counts per servo loop =

4000 x 0.05

=

200

5-20 Operation

MN1904

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Baldor BXII installation manual Tuning an axis for velocity control, Calculating Kvelff
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BXII specifications

The Baldor BXII is a robust and versatile industrial motor known for its high performance and reliability in various applications. Designed for use in demanding environments, the BXII series is particularly favored in the food processing, petrochemical, and material handling industries. Its construction and technological features distinctly differentiate it from other motors in the market, enhancing efficiency and durability.

One of the standout features of the Baldor BXII is its premium efficiency rating, which ensures that the motor operates with minimal energy loss. This efficiency is crucial for industries looking to reduce energy costs and lower environmental impact. The BXII motor meets or exceeds NEMA Premium Efficiency standards, making it an eco-friendly choice for operations requiring continuous power.

Another important characteristic of the BXII series is its advanced design, featuring a high-quality aluminum frame that promotes excellent heat dissipation. This construction enhances the lifespan of the motor and reduces the risk of overheating during extended operation. Additionally, the BXII is equipped with an IP55-rated enclosure, ensuring that it is well-protected against dust and moisture, which is vital for reliability in harsh environments.

The Baldor BXII incorporates state-of-the-art technology in its motor design, including an innovative rotor design that offers optimal torque characteristics. This carefully engineered rotor ensures smooth operation and minimal vibration, resulting in increased performance and reduced wear on mechanical components.

Moreover, the BXII series employs a continuous duty service factor, allowing for longer operational hours without overheating or compromising performance. This is particularly beneficial for applications requiring consistent power output over extended periods.

The integration of smart technologies in the BXII line also enhances its usability. Features such as thermal protection and vibration sensors enable proactive monitoring of motor health, leading to preemptive maintenance that reduces downtime and extends the life of the motor.

Overall, the Baldor BXII offers a winning combination of efficiency, durability, and advanced technology, making it a reliable choice for industrial applications. Its commitment to performance and innovation underscores Baldor's reputation as a leader in the manufacturing of high-quality motors, ensuring that businesses can operate with confidence and efficiency. Whether in a food processing facility or a manufacturing plant, the BXII series stands out as an exemplary choice for those seeking dependable motor solutions.
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