Beijing Leader & Harvest Electric Technologies Co., Ltd.

Variable Frequency Drive

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Start mode setting
Normal start
At normal start status, VFD will start and operate at given frequency in open loop mode, or operate at the expected value of the controlled object in closed loop mode.
Soft start
At soft start status, VFD will start and accelerate to the frequency of power grid regardless of the given frequency. When the output frequency of VFD reaches the frequency of power grid (set in main interface), then the output of VFD will become 0, at the same time VFD sends ' transfer to power grid' command. This command can make the control circuit to transfer the power supply of the motor from VFD to the power grid. During the transient transfer, there is a big inrush current.
For synchronous transfer (OPTIONAL FUNCTION, synchronous transfer reactor is required), both VFD and power grid will supply the power to the motor during the transient transfer, there is very small inrush current.

Operation mode setting
closed loop
In closed loop mode, VFD will automatically adjust the output frequency and operate at the expected value of the controlled object. User can set the expected value of the controlled object, such as pressure, temperature.
open loop
In open loop mode, VFD will operate at given frequency. The given frequency can be set in main interface, external analog signal, or the data bus in the field.

Waveform display ( OPTIONAL FUNCTION)
By sampling the input/output current/voltage, to show the waveform and calculate the power factor and input/output power.
Automatic schedule
User can fill out the schedule timetable for a period of time. VFD will operate automatically at the exact value given in the schedule timetable at the setting time.
Operation log
VFD Operation log can be recorded automatically. Every operation and the accurate time of the operation will be recorded.
Operation record
The parameters recorded include given frequency, motor speed, input current, output current, input voltage, output voltage, the value of controlled object and system status. All parameters recorded will be automatically saved daily in flash memory of the embedded computer integrated with HMI as a txt file. The name of the txt file is the date. The "Record Interval" can be set by the user.
Function lock setting
By setting the local/remote control function lock, the schedule mode, given mode, start mode and operation mode in local/remote control. In local/remote control mode, VFD will run automatically according to the mode selected by the function lock selected.
Motor protection setting
For the special requirement of overload and under-load protection, the user can change the default
value of the protection in this interface.

Bypass function (OPTIONAL FUNCTION)
QF is existing breaker of the user.
If QS1, QS2, QS3 are offline isolator switches, VFD can only be bypassed manually when QF is open.
QS1 and QS2 are close, QS3 is open, the motor is driven by VFD.
QS1 and QS2 are open, QS3 is close, the motor operates in DOL (direct on line) mode. VFD is isolated from the power grid and the maintenance can be done.
If all QS1, QS2 and QS3 are vacuum contactors or breakers, VFD can be bypassed automatically. For soft start or synchronous transfer, all QS1, QS2 and QS3 must be vacuum contactors or breakers.
When bypassing VFD for synchronous motor, the excitation current control from VFD will be transferred to original control mode.
Additional function (OPTIONAL FUNCTION)
Close/open of the valve can be automatically controlled by VFD.

Frequency setting
Given frequency can be set by the computer or by external analog signal.
Computer Given
Set the frequency by the acceleration or deceleration button in the main interface or by ' Given-frequency' button.
Analog Given
Accept 0~10V or 4~20mA external analog signal as the given frequency.

Control mode setting (Local/remote control)
Local control
Control VFD through touch screen interface and buttons on the VFD panel.
The user can operate VFD by the upper PC, i.e. start, stop, emergency stop, reset, setting frequency and browse the log. The user can monitor all the key operating parameters of VFD by the upper PC, i.e. current, voltage, frequency, the actual value of controlled object and alarms. One upper PC can monitor 32 VFDs at the same time.
DCS control
Programmable digital and analog port can be connected to DCS directly by hard cables or by data bus cables through communication protocol (Modbus, Profibus, TCP/IP, DeviceNet, etc).
GPRS remote control ( OPTIONAL FUNCTION)
User can control and monitor VFD in another place via GPRS wireless network.

Parameter setting
All parameters can be made a backup.
Set two frequency-skipping segments to reduces the possible resonance, such as fan resonance.
Set the torque booster for starting different loads.
Set the over-current and over-load protection as per different requirement.
Extendable for the motor control parameters.

Failure self-diagnosis and record
VFD can self-diagnose and record the failure. For light failure, alarm message is displayed in main interface in real time; for serious failure, failure interface and the fault location is automatically displayed.
The user can check the past failures from the failure interface.

Variable Frequency Drive
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