Lenze i700 Uživatelský manuál stáhnout pdf (Strana 154)

5 Motor control & motor settings

5.16 "Short-circuit braking" function

154

Lenze · i700 servo inverter · Reference manual · DMS 1.5 EN · 03/2014 · TD05

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5.16 "Short-circuit braking" function

The control modes for synchronous motors provide the opportunity to use "short-circuit braking" for

the braking process.

Short-circuit braking can be

• parameterised via bit 6 in the Lenze control word (0x2830

or 0x3030 for axis B) or

• as response to light errors. Response of the device in the event of an error

( 262)

Cases of application

• for short-circuit braking via bit 6:

• The braking energy cannot be converted into heat in a brake resistor.

• An external control wants to request short-circuit braking as e.g. an error has been detected

in the encoder system which does not permit braking via quick stop.

• for short-circuit braking as response to light errors:

• Due to an encoder error, no quick stop is possible anymore.

Functional description

The effect of the short-circuit braking on the deceleration behaviour depends on the motor features,

the effective cable length, the mass inertia and the initial value of the speed (application point).

Primarily, short-circuit braking can be used to convert a part of the kinetic energy into heat energy

which serves to unload external brake assemblies and limit position dampers.

If short-circuit braking is to be used as the only holistically effective deceleration unit, it is

recommended to verify the feasibility by tests. For this purpose, bit 6 in the Lenze control word

(0x2830

or 0x3030 for axis B) serves to trigger the short-circuit braking. The oscilloscope function of

the »PLC Designer«/»EASY Starter« serves to record the following important objects:

•Speed: Setpoint speed (0x2DD3:1

or 0x35D3:1 for axis B)

• Speed: Actual speed (0x606C

or 0x686C for axis B)

• Phase currents U, V, W (0x2D83:2...4

or 0x3583:2...4 for axis B)

 Stop!

In some constellations, it is not possible to decelerate the motor speed of a synchronous

motor to zero by means of "short-circuit braking". The braking effect cannot be

compared to the "quick stop" function where the motor is energised under optimal

conditions!

 Note!

The short-circuit current is set freely according to the motor voltage (k

* speed) and the

internal resistance of the system. Thus, it is mandatory that the ampacity of the i700

servo inverter is oriented towards the short-circuit current to be maximally expected.

Guide value: I

max_device

(3 s) ≥ 1.5 * I

max_motor

(according to the data sheet/catalogue)

In case of a deviating assignment, a rating based on the currently possible parameters

(max. speed, max. motor current, field weakening, etc.) is required!

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