Lenze MC3000 Series Manual do Utilizador descarregar pdf (Página 51)

13435743_EDBM301_v14.0 47

10 MIN FRQ (MINIMUM FREQUENCY)

This parameter defines the lower limit of the drive’s speed range. MIN FRQ is used in

conjunction with MAX FRQ (Parameter 11 below) to dene the operating range of the drive.

If MIN FRQ is set to a value above 0.0 Hz, the drive will ramp up from 0.0 Hz when given

a start command. Once running, however, the drive will not operate below the MIN FRQ

setting unless the rotation is changed, or a stop command is issued and the drive is

programmed to ramp to a stop.

If the MINIMUM FREQUENCY is set to 0.0 Hz, the drive may be operated in ZERO SPEED

mode (drive is in RUN state, but there is no output to the motor). ZERO SPEED operation

can be used in applications requiring the ability to start and stop the drive using only the

selected speed reference. The drive will start when the speed reference is raised above

0 VDC or 4 mA, and it will stop when the reference is lowered to 0 VDC or 4 mA. Note

that the drive must be initially started using one of the normal start commands (keypad

or terminal strip).

11 MAX FRQ (MAXIMUM FREQUENCY)

This parameter denes the upper limit of the drive’s speed range. MAX FRQ is used in

conjunction with MIN FRQ (Parameter 10 above) to dene the operating range of the drive.

WARNING!

Consult motor manufacturer before operating motor above rated

frequency. Overspeeding the motor and/or driven equipment can

cause damage to equipment and injury to personnel!

12 DC BRAKE (DC BRAKE VOLTAGE)

DC braking creates a braking torque by injecting DC voltage into the motor. This parameter

sets the magnitude of that DC voltage. The point at which the drive applies DC braking

to the motor depends on which STOP mode is programmed (either COAST or RAMP,

see Parameter 26 - STOP).

If the drive is set to COAST, DC braking is activated when the stop command is given.

In this case, DC braking helps decelerate the motor. This is useful in applications where

a quick deceleration is desired on a load that would normally take a long time to coast

to a stop.

If the drive is set to RAMP, DC braking is activated when the output frequency reaches

0 Hz. In this case, the drive decelerates the load to a near stop and then DC braking is

used to stop and hold the motor. This is useful in applications where the load needs to

be stopped in a certain position. Similar applications with high-inertia loads utilize both

dynamic braking and DC braking. The dynamic braking allows the high-inertia load to be

decelerated quickly, while the DC braking stops the load in the desired position.

Due to heat generated in the motor, DC braking should only be used in applications

where the load is stopped infrequently. In high duty-cycle applications, dynamic braking is

recommended because the heat is dissipated through external resistor banks, rather than

in the motor. When used, DC BRAKE should be set to the lowest voltage that provides

satisfactory operation in order to minimize motor heating. The maximum voltage available

depends on the voltage rating of the drive.

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