Voltage Ramp mode
The simplest type of soft start with the SIRIUS 3RW44 is achieved using auto voltage ramp. The terminal voltage of the motor is increased from auto parameterizable start voltage to line voltage within an adjustable starting time. This starting mode is preset in the quick start menu.
Start voltage
The level of the start voltage determines the switch-on torque of the motor. Auto smaller start voltage results in a smaller start torque and smaller starting current.
The start voltage should be high enough so that the motor starts immediately and softly when the start command is sent to the soft starter.
Starting time
The length of the starting time determines the time in which the motor voltage is increased from the set start voltage to the line voltage. This influences the acceleration torque of the motor, which drives the load during the run-up procedure. A longer starting time results in a smaller acceleration torque over the motor run-up. This results in a longer and softer motor run-up. The length of the starting time should be selected such that the motor reaches its nominal speed within this time. If this time is too short, i.e. if the starting time ends before the motor has run up, an extremely high starting current will occur at that moment, reaching the value of the direct starting current at this speed. The soft starter can, in this case, switch itself off via the internal overload protection function and go into fault mode.
Maximum starting time
The "Maximum starting time" parameter is used to determine the time after which the drive should have fully run up. If the drive is not in nominal operation upon completion of the set time, the starting procedure is aborted and an error message is generated.
Internal run-up recognition
The soft starter features internal run-up recognition. If a completed motor run-up is recognized by the device, the internal bypass contacts will close and the thyristors are bridged. If this run-up recognition is performed before the set run-up time is completed, the ramp is aborted and the motor voltage is immediately increased to 100 % of the line voltage before the internal bypass contacts are closed.
Typical applications for voltage ramps
The voltage ramp function principle is suitable for any type of application.
If test runs are carried out using motors that are smaller than those used in actual applications, we recommend using the "Voltage ramp" starting mode.
For machines requiring a breakaway pulse (inverse load response, e.g. in mills or crushers), the breakaway pulse must be set.
"Breakaway Pulse in Combination with the Voltage Ramp or Torque Control Starting Mode". The "voltage ramp+current limiting (U+current limiting)" starting mode is recommended for heavy starting
Torque Control mode
The motor speed and torque is calculated using the voltage and current R.M.S. values as well as the associated phase information between the line voltage and the motor current (= cos ϕ= sensorless control) and the motor voltage is controlled accordingly.
Torque control means that the torque generated in the motor is linearly increased from a parameterizable start torque up to a parameterizable end torque within an adjustable starting time.
The advantage over the voltage ramp is improved mechanical run-up behavior of the machine.
The soft starter controls the torque generated at the motor continuously and linearly according to the set parameters until the motor has completely run up.
For optimum torque control during the stopping process, the motor data of the motor connected to the soft starter should be entered in the selected parameter.
This can be specified using the "Setting" menu item.
Start torque
The height of the start torque determines the switch-on torque of the motor. Auto smaller start torque results in a smaller run-up torque and smaller starting current. The start torque should be high enough so that the motor starts immediately and softly when the start command is sent to the soft starter.
Limiting torque The level of the limiting torque determines which maximum torque should be generated in the motor during running up. This value can thus also act as an adjustable torque limitation.
In order to obtain a successful run-up, the parameter value should be set to about 150 %. It should be at least high enough so that the motor does not get stuck during startup. This ensures that enough acceleration torque is generated throughout the entire motor run-up phase.
Starting time
The length of the starting time determines the time in which the start torque is increased to the end torque.
A longer starting time results in a smaller acceleration torque over the motor runup.
This results in a longer and softer motor run-up. The length of the starting time should be selected such that the motor accelerates softly until it reaches its nominal speed.
If the starting time ends before the motor has completely run up, the torque is limited to the set limiting torque until the soft starter recognizes the run-up process and closes the internal bypass contacts.
Maximum starting time
The "Maximum starting time" parameter is used to determine the time after which the drive should have fully run up. If the drive is not in nominal operation upon completion of the set time, the starting procedure is aborted and an error message is generated.
Internal run-up recognition
The soft starter features internal run-up recognition. If a completed motor run-up is recognized within the defined starting time, the ramp will be aborted and the motor voltage will immediately be increased to 100 % of the line voltage. The internal bypass contacts will close and the thyristors are bridged
Note
The torque generated in the motor and controlled by the soft starter can at no time be higher than the value of a similar direct start at the same speed.
Typical applications for torque control
Torque control is suitable for all applications, especially in cases where auto homogeneous and smooth run-up is required. For machines requiring auto breakaway pulse (inverse load response, e.g. in mills or crushers), the breakaway pulse.”Breakaway Pulse in Combination with the Voltage Ramp or Torque Control Starting Mode". The "Torque control+current limiting (M+current limiting)" starting mode is recommended for heavy starting
Breakaway Pulse in Combination with the Voltage Ramp or Torque Control Starting Mode
This function is required for load machines with inverse torque behavior. Typical applications are mills, crushers or drives with plain bearings. In such cases it may be necessary to create a breakaway pulse at the beginning of the machine’ station start process. The breakaway pulse is set via the breakaway voltage and the breakaway time. Using the breakaway pulse, the high limiting friction of the load can be overcome and the machine can be set into motion.
The breakaway pulse can be used in combination with the voltage ramp, torque control or current limiting starting modes and is superimposed on these during the whole breakaway time.
Breakaway voltage
The breakaway voltage setting determines the breakaway torque to be generated. Its maximum value can be 100 % of the start torque generated on direct starting. The pulse should be high enough for the motor to start immediately when the soft starter receives the start command.
Breakaway time
The breakaway time specifies how long the breakaway voltage should be applied. Upon completion of the breakaway time, the soft starter finishes its run up process with the selected starting mode, e.g. voltage ramp or torque control.
The selected breakaway time should be at least long enough so that, after the configured time has elapsed, the motor does not remain stationary again but rather accelerates further in the selected starting mode.
If 0 ms is set as the breakaway time (default), the breakaway pulse function is deactivated
Typical applications for breakaway pulses
Typical applications for breakaway pulses are load machines with inverse torque behavior, e.g. crushers and mills.
Note
A breakaway pulse that is too high may lead to the error message "Current measurement range exceeded".
Remedy: Use larger starter dimensions or a lower breakaway voltage.
Only set the breakaway pulse when it is really required (e.g. for mills for crushers).
A wrongly set breakaway pulse, e.g. for pumps, may lead to the error message
"Incorrect start conditions
Current Limiting in Combination with the Voltage Ramp or Torque Control Starting Mode
The starter continuously measures the phase current (motor current) using the integrated current transformer.
During motor run-up it is possible to set a current limit value on the soft starter. The current limiting can be activated if "Voltage ramp+current limiting" or "Torque control+current limiting" have been selected as starting mode and auto value has been entered in the relevant parameter.
During the starting procedure, the phase current is limited to the set value until it falls below this value. A defined breakaway pulse is superimposed on the current limiting during the breakaway time.
Current limit value
As a factor of the motor rated current, the current limit value is set to the maximum current required during the starting procedure. If the set current limit value is reached, the motor voltage is lowered (or controlled) by the soft starter such that the current will not exceed the set current limit value. The configured current limit value must be selected high enough that enough torque can be created in the motor in order to bring the drive into the rated area of operation. Auto typical value is 3-4 times the value of the rated operating current (Ie) of the motor.
Run-up recognition
The soft starter features internal run-up recognition. If a completed motor run-up is recognized, the motor voltage is immediately increased to 100 % of the line voltage. The internal bypass contacts will close and the thyristors are bridged.
Typical applications for current limiting
Used in applications with a large centrifugal mass (mass reactance) and hence long starting times, e.g. large fans, in order to lighten the load on the supply network
Starting Mode: Direct On-line
If the "Direct on-line" starting mode is set, the motor voltage is immediately increased to line voltage when it receives the start command. This resembles the starting behavior with a contactor, i.e. the starting current and start torque are not limited.
Note
Due to the high starting current of the motor, the error "Current limit exceeded" may occur in direct on-line starting mode. It may be necessary to select a larger dimensioned soft starter.
Run-up recognition
The soft starter features internal run-up recognition. If a completed motor run-up is recognized, the internal bypass contacts will close and the thyristors are bridged.
Starting Mode: Motor Heating
If IP54 motors are used outdoors, condensation occurs in the motor during cooler periods (e.g. overnight or in the winter). This may lead to leakage currents or short circuits when the devices are switched on.
A pulsating DC current is fed into the motor winding to warm it up.
If the "Motor heating" starting mode is selected, a heating capacity can be entered in the settings. This capacity should be chosen in such a way that the motor will not be damaged. The setting range for the heating capacity extends from 10 - 100 %. This corresponds to a motor current of approximately 5 - 30 % of the motor rated current.
Typical applications for motor heating mode
Used e.g. in outdoor drives to minimize condensation inside the motor.
Caution
May lead to damage to property.
The motor heating starting mode is not a continuous operating mode. The motor must be equipped with a temperature sensor (Thermo click/PTC) to ensure motor protection. The motor model with integrated electronic motor overload protection is not suitable for this kind of operation.
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