Mv variable frequency drive

Types of MV variable frequency drives

Paging and beating the MV variable frequency drive in the first place is mainly for large motors. These and other electrical appliances operate at 230, 400, 660, and, in some cases, 3,300 volts.

Operational frequencies are usually 50 or 60 Hz - which are standard in electrical generation and supply systems.

An MV drive must be used with a transformer or autotransformer (often called a "PT" or "Potential Transformer") to reduce the power supply voltage for the drive installation or local electrical distribution network to a safe level.

Theatrical drives are generally connected to electric motors used in high-power applications. Some applications include:

• Water and wastewater treatment facilities using pumps and aeration equipment.
• Mining operations that utilize large hoists, compressors, and fans.
• Paper manufacturing processes requiring sizable motors for grinding, pulping, and pressing.
• Power generation facilities using big turbines, pumps, and fans to maintain operations.
• Oil and gas extraction and processing, including offshore platforms with extensive motor requirements.
• HVAC systems with large fans, chillers, and pumps for commercial and industrial building climate control.
• Steel, aluminum, and other metal processing plants with heavy machinery requiring significant motor power.
• Chemical mixing, conveying, and processing in plants that manufacture industrial chemicals and products.

Industrial applications of MV variable frequency drives

The MV variable frequency drives play a crucial role in improving energy efficiency and extending the lifespan of motors in various industrial applications. Below are some specific situations in which these drives are used in an industrial setting:

• Pump systems: Pumps used in water supply, wastewater treatment, and irrigation systems benefit from MV drives by controlling the speed based on the required flow rate and pressure. This is a very smart way to do things because it reduces energy waste and helps avoid damage to the system due to overpressure or cavitation. Using an MV drive on pumps also helps remove excess water from areas prone to flooding, thus efficiently keeping water levels low and reducing flooding risks.
• Fans and blowers: The fans and blowers that circulate air in large buildings or industrial processes use MV drives to adjust the fan speed to match airflow requirements. This precise adjustment helps increase the airflow over heating/cooling systems and maintains proper ventilation in buildings and within machinery. Plus, lower fan speeds during off-peak times help reduce energy consumption and noise, making the environment more comfortable.
• Compressor control: Compressors that provide critical gases for chemical processes or pneumatic tools have an associated MV drive that controls the output pressure and flow based on system needs.
• Conveyor systems: The long belts and other parts that move materials around within and between factories use powerful VFDs to adjust the speed based on the load carried at any given time. Besides, this capacity to adapt protects both the conveyor itself and the materials moved from excess force that could cause damage.
• Crushing and grinding equipment: Crushers, ball mills, and other size-reduction equipment for rocks, ores, and cement place intense demands on motors, so using VFDs to vary their speed based on material conditions will help prevent motor overloading and improve the drive's lifespan.
• Mixers and agitators: The mixing vessels used to combine chemicals or other materials and large storage tanks containing viscous liquids churned up have associated MV drives to precisely control the stirrer or impeller speed.
• Elevators and lifts: Large industrial elevators used in construction and mining and lift trucks designed to hoist loads many stories up and down all rely on MV drives for smooth speed changes and load torque matching. Using drives and not just mechanical brakes or governors helps prevent excessive wear and tear and makes many vertical transports safer and more comfortable for users.

Therefore, with the drives allowing for smooth speed adjustments and protecting the motors from overload and mechanical stress, the overall operational efficiency in these industrial environments is greatly optimized.

Product specifications and features of MV variable frequency drives

Key features

• IGBT Power: The inverter stage of the drive, built with insulated gate bipolar transistors (IGBTs), can efficiently power motor rotation regardless of load conditions with great torque and a smooth running experience.
• True rms: The drive can measure voltage and current waveforms accurately, regardless of the shape, to ensure precision motor control and eliminate mistakes typical of average value calculations.
• Open loop vector: The drive self-adjusts to maintain the desired speed regardless of load changes, even without a feedback device, providing good performance where installing a sensor is complicated or impossible.
• Smart Motor Control: Motor protection and control algorithms are embedded in the MV drive to protect the motor from overheating and provide a long life through optimum use and reduction of overcurrent and torque.
• SPLC: The special speed control method embedded in the drive enables very fine speed control to within 1 RPM or less, critical for applications where precise speed maintenance is vital even with load fluctuations.
• Integrated PLC: The MV drive also has programmable logic controller functions embedded in it to allow users to develop customized control programs without needing an external PLC for a high degree of process control flexibility.
• V/f control: Voltage and frequency control are adjustable in conjunction with each other to enable simplified control of different motor speeds under varying loads while protecting the motor from overheating due to excessive torque.
• Open loop and closed loop: There is the option for either open-loop control, which does not require feedback regarding motor position/speed from an external device, or closed-loop control, which utilizes such feedback. This accommodates various applications and user preferences, as a position transducer may or may not be required.

How to install

• Mounting the VFD: Select a location near the motor and pump where the VFD can stay dry and out of direct heat/sunlight. Mount it on a stable surface.
• Wiring to power: Turn off all electrical systems and use a multimeter to verify no current. Connect the VFD to the main power supply wires per the wiring diagram in the manual.
• Wiring to motor: Cut the motor wires to the respective terminals on the VFD as shown in the manual's diagrams.
• Installing a potentiometer: Drill a hole near the VFD where the user can easily access it and mount the potentiometer through the hole. Wire the potentiometer leads to the VFD according to the accompanying diagram.
• Replacing the drive belt: Remove the cover or guard to access the old drive belt. Loosen the tensioner pulley and remove the old belt from the pulleys. Slide a new belt over the motor and driven pulleys and re-tension the pulley.
• Completing the electrical connection: Close the drive end terminals in the VFD to ensure a secure connection and prevent exposed wires. Use wire nuts to connect corresponding color-coded wires. Close the cover after making all electrical connections.

How to use

• Turning on the hydraulic system: The first step is to turn on the main power supply to the hydraulic system so that all components can receive the necessary electrical energy for operation.
• Starting the motor: The MV VFD is then activated by turning on the relevant switches or controls on the drive interface.
• Adjusting frequency: By turning the control knob or pushing the associated buttons, the frequency output of the drive can be varied. Increasing the frequency will increase the rotational speed of the motor and, consequently, the hydraulic pump's flow rate.
• Monitoring parameters: Throughout operation, it is critical to monitor key parameters such as motor speed, pump flow rate, and system pressure to ensure the hydraulic system performs within desired operating limits and efficiently meets the application's load and demand requirements.

Maintenance and repair

• Maintenance: Check every part regularly, including bearings, pulleys, belts, and the VFD. Re-lubricate where required. Replace parts like bearings that wear out. Ensure the VFD doesn't overheat by checking and cleaning its cooling fan.
• Repair: Once any defects like crack belts, faulty pulleys, or worn-out bearings are spotted, the damaged parts must be replaced. Torn drive VFD drives must also be repaired. Essential electrical paths or areas must also be repaired.

Quality and safety considerations of MV variable frequency drives

Safety consideration

• Electrical hazards: The motor cables and electrical components of the drive operating area contain potentially dangerous high-voltage electrical currents. These currents can lead severe injury or be fatal if touched. The safety of electrical areas has to be prioritized by ensuring people do not touch ungrounded parts and by using properly rated personal protective equipment, such as insulated tools and gloves.
• Mechanical hazards: There are rotating parts such as fans and pulleys, which are mechanical hazards that can lead to injury through entanglement or contact. These components should be regularly inspected and repaired, and proper maintenance has to be carried out while guarding around drive area provided to limit contact.
• Fire hazards: High-power electrical devices can cause fires if overheating occurs or if there are electrical faults. Excessive electrical loads or failure to maintain proper ventilation can result in overheating. There should be constant checking on electrical connections and the drive system for any signs of damage, which could lead to fire, and ensure proper grounding of equipment to reduce risks.
• Vibration and noise: High-frequency vibration in electrical equipment can lead to discomfort and possible long-term adverse effects on the operator, whilst motor drive noise can be disturbing and harmful to hearing. The impacts of vibrations on nearby structures should be monitored and cushioned using vibration-isolating mounts. Hearing protection should be worn around noisy motors and drives when in use.

Quality checks

• Incoming material inspection: The VFDs and other electrical components sourced from suppliers should be scrutinized to ascertain their quality and ensure they conform to purchase order specifications.
• In-process quality control: During the installation of VFDs in the electrical panel, constant monitoring must be done to ensure all wiring, fastenings, and other activities are performed per set standards.
• Functional testing: Every unit of VFDs produced must undergo operational and performance testing to check for the ability to handle variable speed, fluctuating loads, and VFD motor heating during normal operation.
• Final inspection: Prior to dispatch, a thorough visual exam as well as performance tests should be conducted on VFDs to verify adherence to specifications and VFD accuracy.
• Compliance verification: The electrical equipment and VFDs should bear certification marks from governmental agencies signifying compliance with established safety and electrical standards.

FAQs

Q1. What benefits do variable speed drives and electronic gearing offer together?

A1. E-gearing enables mechanical systems to smoothly transfer motor power as needed, depending on the application and workload requirements. On the other hand, VSDs optimize motor operation by adjusting rotation speed in line with load demands, leading to more effective energy usage and operation.

Q2. What is the main function of a motor starter in an MV VFD installation?

A2. The motor starter acts as a main switch between the VFD output and the motor. It disconnects the motor from the VFD during maintenance or fault conditions to prevent hazards.

Q3. What's the difference between a variable frequency drive and a servo drive?

A3. VFDs control AC motor speed using voltage and frequency adjustment, ideal for constant torque applications. In contrast, servo drives provide precise position, speed, and torque control using feedback mechanisms, better suited for dynamic, high-precision tasks. Essentially, VFDs offer broad speed control for general use, while servo drives enable fine control for specific, high-performance needs.

Q4. Can an MV VFD be used outdoors?

A4. Outdoor usage is permitted only if the VFD has been specifically designed in a weatherproof enclosure. While VFDs can be installed outside, ensuring proper protection from weather elements is crucial for maintaining their functionality and durability.

Q5. What's the role of a "bypass" in an MV VFD system?

A5. A bypass lets users switch from the VFD control to direct motor power supply. This is essential for maintenance or emergencies so the motor can still operate without VFD assistance.