Program 2011/2012 - maxon motor - #35

DC tacho control

The motor must be equipped with a DC tachom-

eter that provides a speed proportional signal.

In the maxon modular system, the tachometer

rotor is mounted directly on the through motor

shaft, resulting in a high resonant frequency.

- Classical solution of a very precise control

- Limited service life of the DC tacho

generator

- Not suitable for positioning tasks

- Only for analog controllers

- Only for DC motors

- Ideal for stringent demands on speed

dynamics

Operating quadrants

4-Q operation

- Controlled motor operation and braking

operation in both rotation directions

- A must for positioning tasks

1-Q operation

- Only motor operation

(Quadrant I or Quadrant III)

- Direction reverse via digital signal

- Typical: amplifier for EC motors

Linear power stage

The operating voltage is divided between the

motor and the power amplifier. The controller

changes the voltage on the motor (UM) linearly

and proportionally. The voltage applied to the

power amplifier (UT) causes power dissipation

- High currents and low motor voltages cause

significant power dissipation

- Simple and favorably priced design of

the power amplifier

Principle: Linear power amplifier

GNDQ.

Pulsed power stage (PWM)

The controller switches the motor on and off in

short intervals (pulses/cycles). If the off interval

is longer, the motor loses speed. The decisive

average value of the voltage changes in rela-

tion to the on-to-off time. Only little energy is

converted into heat.

- More expensive power amplifier

For further explanations, please see page 279. - High efficiency

Principle: DC tachometer control

Operation quadrants

Principle: Pulsed power amplifier

maxon motor control

+ Ï

_>|-<M>J

Quadrant II

Braking

CW

May 2011 edition / subject to change

Technology - short and to the point 35