Variable Speed Drives
Variable Speed Drives (VSDs), also known as adjustable speed drives, are large industrial electric motors whosespeed can be adjusted by means of an external controller. They are used in process control and help saving energy in plants that use many powerful electric motors.
Variable Speed Drives (VSDs), also known as adjustable speed drives, are large industrial electric motors whose speed can be adjusted by means of an external controller. They are used in process control and help saving energy in plants that use many powerful electric motors.
The use of adjustable speed in process control matches the motor speed to the required tasks and may compensate for changes in the process's variables. The use of adjustable speed for saving energy is exemplified by the adjusting the speed of a colling fan motor to match the temperature of the machinery parts it is cooling.
VSDs are effective in energy savers in pump and fan applications; "they enhance process operations, particularly where flow control is involved. VSDs provide soft-start capabilities, which decrease electrical stresses and line voltage sags associated with full voltage motor start-ups, especially when driving high-inertia loads."
Adjustable frequency drives are a specific type of VSDs; they are controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor.
Most variable speed drive manufacturers require a reference to the neutral point of the winding, particularly for larger equipment. This connection serves as their primary "check" for unbalance in phase-phase and phase-ground circuits. As a side benefit, it keeps the VSD from accidentally damaging the machine winding insulation by over-voltaging the terminals by keeping the VSD and motor neutral at the same value.
Variable speed drive on cooling tower fans
Cooling tower pumps are fixed speed but we have variable speed drives on the cooling tower fans. These do a good job of controlling the cooling tower supply temperature except in those installations where the cooling tower sump size is excessive. With the flow control valves on the individual exchanges, the variable speed drive may not be absolutely necessary, but the process temperature control works better if it doesn't have to deal with daytime to nighttime or storm induced variation in supply temperature.
Variable speed drive Restoration
Restoration of variable frequency drive that have been exposed to excessive moisture or have been in a flood pose a more difficult challenge. A typical variable speed drive contains a wide range of operating voltages and power supplies, complicated printed circuit boards and intricate control circuits. The severity of damage to the variable speed drive usually will depend on whether or not the variable speed drive was operating when the exposure occurred. The damage that occurs is most likely more severe if exposure occurs while the variable speed drive is operating. If the variable speed drive is exposed while it is not energized, the damage can be less severe but will usually be latent in nature. In either case, if any input line or internal power supply fuse is open or significant corrosion is present, contact the manufacturer for specific corrective measures.
Variable speed drive in water pump station
Controlling pumps by variable speed drive improves production and site environment, and meet technics requirement completely. Integration of PLC control, Profibus technology and medium voltage variable speed drive leads to high automatization level, stable operation, easy operation and considerable energy saving.
Variable speed drive problems
When an application requires more current at a reduced speed, that means more heat and less cooling at the lower speeds. Most VSDs have limits to protect the VSD and consequently the motor. Too low a setting and there will be lot of trips. Too high a setting and there may be damage in high ambient temperatures.
If the pump has to operate at its max HP, the 125% may not be enough given the losses (excess current) required by the variable speed drive, especially with long feeders. In addition, noise from other high frequency devices like other variable speed drives, arc welders, etc can cause problems with the variable speed drive as well as the variable speed drive causing other problems on the electrical service. A line reactor or filter may be required there also. The lower the carrier frequency is, typically 2 KHz to 4 KHz, the noisier the motor but less losses and more efficient. The higher the carrier frequency, the quieter the motor operation but greater loses and more line current.
Variable speed drive on fan for air flow control
At present, competition is very intense. The key is cost. Power consumption of motor accounts for 30% of cost. Motor driving fan is a big part. So it is very important to reduce consumption of motor. Today, phenomenon of "large horse drives small dolly" is serious. If technology of variable speed is adopted, it not only satisfies production requirement but also saves energy. Meanwhile, variable speed drive saves a lot of energy source and improves efficiency for plant. After innovation with variable speed drive, energy saving rate is in 30-50%. The investment usually recovers in one or two years.
Contact RSA Bardo Electrical Systems for your Variable Speed Drive Installations.