Normal/High Overload Torque Control,Open Loop; Programming Of Torque Limit And Stop - Danfoss VLT 5000 Series Instruction Manual

Normal/high overload torque control,open loop

This function enables the adjustable frequency drive
to perform a constant 100% torque, using an oversize
motor.
The choice between a normal or a high overload tor-
que characteristic is made in parameter 101.
This is also where to choose between a high/normal
constant torque characteristic (CT) or a high/normal
VT torque characteristic
If a high torque characteristic is chosen, a rated motor
with the adjustable frequency drive obtains up to 160%
torque for 1 min. in both CT and VT. If a normal torque
characteristic is chosen, an oversize motor allows up
to 110% torque performance for up to 1 min. in both
CT and VT. This function is used mainly for pumps and
fans, since these applications do not require an over-
load torque.
The advantage of choosing a normal torque charac-
teristic for an oversize motor is that the adjustable
frequency drive will be able constantly to yield 100%
torque, without derating as a result of a bigger motor.
NOTE
This function cannot be chosen for VLT
5001-5006, 200-240 Volts, and VLT
5001-5011, 380-500 Volts.
Internal current regulator
The VLT 5000 features an integral current limit regu-
lator which is activated when the motor current, and
thus the torque, is higher than the torque limits set in
parameter 221 and 222.
When VLT 5000 Series is at the current limit during
motor operation or regenerative operation, the adjust-
able frequency drive will try to get below the preset
torque limits as quickly as possible without losing con-
trol of the motor.
While the current regulator is active, the adjustable
frequency drive can only be stopped by means of ter-
minal 27 if set to Coasting stop, inverse [0] or Reset and
coasting stop, inverse [1]. A signal on terminals 16-33
will not be active until the adjustable frequency drive
has moved away from the current limit.
Please note that the motor will not use the ramp-down
time, since terminal 27 must be programmed for
Coasting stop, inverse [0] or Reset and coasting stop,
inverse [1].
206
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VLT 5000 Series

Programming of Torque limit and stop

In applications with an external electro-mechanical
brake, such as hoisting applications, it is possible to
stop the adjustable frequency drive via a `standard'
stop command, while at the same time activating the
external electro-mechanical brake.
The example given below illustrates the programming
of adjustable frequency drive connections.
The external brake can be connected to relay 01 or 04,
see Control of mechanical brake on page 66. Program
terminal 27 to Coasting stop, inverse [0] or Reset and
coasting stop, inverse [1], as well as terminal 42 to
Torque limit and stop [27].
Description:
If a stop command is active via terminal 18 and the
adjustable frequency drive is not at the torque limit, the
motor will ramp down to 0 Hz.
If the adjustable frequency drive is at the torque limit
and a stop command is activated, terminal 42 Output
(programmed to Torque limit and stop [27]) will be ac-
tivated. The signal to terminal 27 will change from
'logic 1' to 'logic 0' and the motor will start coasting.
- Start/stop via terminal 18.
Parameter 302 = Start [1].
Quickstop via terminal 27.
-
Parameter 304 = Coasting stop, inverse [0].
- Terminal 42 Output
Parameter 319 = Torque limit and stop [27].
- Terminal 01 Relay output
Parameter 323 = Mechanical brake control
[32].
MG.51.C5.22 - VLT is a registered Danfoss trademark.