Starting and stopping a motor can be done with three common methods: a motor starter, soft start or variable frequency drive (VFD). As of late, the use of a VFD is becoming more popular than ever due to its claimed efficiency benefits but be sure it is needed. And, once specified, it must be properly installed to ensure reliable operation.
Why is VFD Panel Installation Necessary?
A Variable Frequency Drive or VFD or Variable Speed Drive is a kind of alterable speed drive utilized in electro- mechanical drive systems to regulate AC motor torque and speed by changing motor input voltage and frequency.
The VFD, often called an ac drive or inverter, takes a single- or three-phase signal and varies the speed of a three-phase ac induction motor. This is its main benefit. Running a motor more slowly can save significant energy, and speed changes may be useful to the application. Another big benefit is adjustable acceleration and deceleration. A smaller amount of acceleration can unstiffen the mechanical forces at starting /of the motor and reduce inrush current. The VFD also has built-in overload protection and motor start/stop control functions.
Variable frequency Drive, better known as VFD Control panel is a complete enclosure that helps to protect numerous electronic components and also VFD in the first place. Exposing VFD dust and windy environment can affect the drive to a great extent and that is why it is important to get VFD Panels installed.
One of the main reasons why VFD control panels have become so important is because they help to keep all electric components in one single place. In fact, it is treated as a comprehensive control solution for harmonic filtering, bypass and various other electric solutions. Over the years, control panels for VFD have gone under the scanner for improving the efficiency, but the ones that are used now are completely safe and highly functional.
Benefits of VFD
- Controlled Starting Current
- Reduced Power Line Disturbances
- Lower Power Demand on Start
- Controlled Acceleration
- Adjustable Operating Speed
- Adjustable Torque Limit
- Controlled Stopping
- Energy Savings
- Reverse Operation
- Elimination of Mechanical Drive Components
What is Done During VFD Panel Installation and Commissioning?
There are both physical and electrical installation basics to be aware of when using a VFD. When mounting the VFD on a back panel, be sure to check the specifications. It is common for multiple devices to be installed in one location, but all VFDs need proper air flow, so check the installation instructions carefully when laying out a control panel. Mount the drives vertically.
- Electrically, proper run/stop control of the VFD is important. Many manufacturers do not recommend using contactors or disconnect switches on the line or load side of a VFD for run/stop control of the ac drive and motor, except for emergency situations. Opening a contactor at the line or load side of a VFD while the motor is running can cause failures in the inverter section of the drive or reduce its life.
- With any motor control circuit, proper overcurrent and ground-fault protection is required at the input of the device. A normal VFD takes single-phase voltage, but it isn’t planned for usage with single-phase motors. Although a standard three-phase induction motor works with a VFD, a three-phase inverter duty motor should be used.
- There are many more factors, features and functions to consider when using a VFD, so study the catalogs and manuals and then get with your vendors. With constant-speed or constant-torque applications, like compressors, conveyors or mixers, there might be easier possibilities. However, whether replacing a dc motor or varying the speed and acceleration of your conveyor, fan, blower or pump, go with the VFD option. It’s often the best choice, if installed properly.
- Cooling: VFD control units must be placed in positions where the highest ambient temperature doesn’t surpass 40˚C. This is a common temperature rating for most units. If higher ambient are expected, derating of the variable frequency drive may be required.
- Supply line power quality: The supply to the VFD input mustn’t change minus or plus ten percent as most VFDs will trip through a protective error. This voltage steadiness must be taken into consideration while operating conductors to the VFD and voltage drops must be found out for long runs.
- Electrical connections: The installation and sizing of VFD load and line conductors must obey the NEC or similar appropriate local codes.
- Grounding: For dependable and safe functioning, all VFDs should be correctly grounded. This usually demands for a grounding conductor to be taken back to a single point grounding position, generally chosen to be at the service. Along with that, a grounding conductor should also be carried back from the motor to the VFD’s inner grounding terminal.
- Fault protection: Numerous VFD have short-circuited shield, in the form of fuses, previously fit by the manufacturer. This is usually the case on larger hp units. Minor units need external fuse shielding. In any of these case, the sixing and choice of these fuses is vital for shielding a semiconductor in the event of an error.
- Motor protection: All motors require overload protection. The utmost customary practice is the utilization of a motor overcurrent relay system that would shield all 3 phases and shield in contradiction of single-phasing.
- Humidity and moisture: in both electrical and electronic equipment, large corrosive atmospheres and humidity are worrisome. VFD units must be mounted in a non-corrosive position at any time, with ambient humidity ranging between zero to ninety five percent noncondensing.
How is VFD Panel Installation and Commissioning Performed?
The process of setting up the parameters of the drive adds additional time for commissioning and installation, and is most easily completed by copy/paste tools which have many positive functions such as:
- The ability to copy the parameter set from one drive to the next
- Able to store parameters to maintain the parameter set for a different application configuration
- Can be used to easily replace downed or failed drives
These tools can easily decrease how complex the processes of installation, commissioning, and troubleshooting may become.
- VFDs are installed at Fan Pump motors.
- Fan pump motor responsible for providing stock to the Head Box
- Head Box requires a control of either head or level
- Control of a level or pressure in Head Box is done by VFITD
A reference signal is fed to the VFD and using a comparator, an error signal is generated based on the deviation of current value from the reference value. The controller in the VFD, then, increases/ decreases the speed based on the signals generated
Input AC Power
- Circuit breakers feeding the VFDs are recommended to be thermal-magnetic and fast acting.
- They should be sized as 1.5 times the input amperage of the drive. Refer to the table below.
- Each VFD should be fed by its own breaker. If numerous drives are to be united on the same breaker, every drive must have its own protection measure from the breaker.
- Input AC line wires should be run in conduit from the breaker panel to the drives. Using a single conduit, AC input power to several VFDs can be driven, if necessary.
- The VFD should be grounded on the terminal marked PE.
- Motor wires from each VFD to its respective motor MUST be run in a separate steel conduit away from control wiring and incoming AC power wiring to avoid noise and crosstalk between drives.
- If the gap among the VFD and the motor exceeds two hundred and fifty feet, an output reactor must be utilised amid the VFD and the motor. The output reactor should be sized accordingly.
- If the distance between the VFD and the motor is between 500 and 1000 FT, a dV/dT filter should be used.
- No contactor must be fit amid the motor and the drive. Operating such a device while the drive is running can potentially cause damage to the power components of the drive.
- When a detach switch is fit amid the motor and the drive, it must only be activated when the drive is in a STOP stage.
An example of programing is given below:
The Drive should be programmed for the proper motor voltage.
- The Drive should be programmed for the proper motor overload value
- To enter the PROGRAM mode to access the parameters:
- Press the Mode (M) button. This will activate the password prompt (PASS).
- Use the Up and Down buttons to scroll to the password value and press the Mode (M) button. After entering the right password, the display will show that the PROGRAM mode has been opened or assessed at the starting of the parameter menu.
- Use the Up and Down buttons to scroll to the desired parameter number.
- After the wanted parameter is located, press the Mode (M) button to exhibit the current parameter adjustments. The parameter value will begin blinking, indicating that the present parameter setting is being displayed. The value of the parameter can be changed by using the Up and Down buttons.
- Pressing the Mode (M) button will store the new setting and also exit the PROGRAM mode. To alter a different parameter, press the Mode (M) button once more to enter the PROGRAM mode again. If the Mode button is pressed within 1 minute of exiting the PROGRAM mode, the password is not required to access the parameters. After one minute, the password must be re-entered in order to access the parameters again.