An Introduction to AC Drives
Published on : Friday 07-07-2023
Why Danfoss drives for heavy industries and harsh environments are advantageous for your organisation.
An AC drive is a device used to control the speed of an electrical motor in order to:
1. Enhance process control
2. Reduce energy usage and generate energy efficiently
3. Decrease mechanical stress on motor control applications
4. Optimise the operation of various applications relying on electric motors
5. Drives can also be utilised to convert energy from natural and renewable resources like the sun, wind or tides, and transmit it to the electrical network or use it for local consumption. In hybrid technologies, AC drives are used to combine conventional energy sources and energy storages to create total energy management solutions.
AC drives are also known by various other names such as adjustable speed drives, adjustable frequency drives, variable frequency drives, variable speed drives, frequency converters, inverters and power converters.
How does a Variable Frequency Drive operate?
A variable frequency drive takes in fixed AC voltage and frequency into a rectifier bridge to convert the voltage to DC, uses a capacitor bank and inductors to filter the DC, then inverts the DC voltage back to AC and sends it out to the motor at the frequency desired.
i. A microprocessor or digital signal processor (DSP) communicates with the PLC and user (via an HMI or keypad), oversees motor operation and checks for faults.
ii. Control circuitry coordinates the switching of power devices to activate the power components in the right sequence. The motor speed varies by changing the voltage and frequency supplied by the output devices.
iii. Basic VFDs maintain motor torque by keeping the volts-to-frequency ratio constant. Advanced units use more intelligent and adaptive algorithms to improve motor performance to the frequency desired.
In short, a VFD translates one voltage and frequency to another to change motor speed without losing torque.
Features of Danfoss drives
Compact drives: Up to 40 percent smaller than other AC drives with comparable power and built-in features.
Protection for electronics: To ensure a long service life, the cooling air does not flow directly over the power electronics. PCBs have industrial 3C3 grade conformal coating as standard.
IP rating: Available in IP00 to IP65 enclosures.
Easy to use: A USB port provides easy PC connectivity. The VLT® Memory Module MCM 102 option facilitates fast implementation of factory settings, transfer of settings, and easy commissioning.
HVAC inside: The VLT® HVAC Drive FC 102 is especially engineered for building automation with intelligent HVAC functions.
Integrated Motion Controller: The Integrated Motion Controller software enables the VLT® Automation Drive FC 302 to run induction and PM motors in positioning and synchronization applications, both with and without encoders.
Focusing on water and pumps: Dedicated functions such as burst pipe monitoring, dry-running protection and flow compensation secure and empower your pumping application independent of the motor technology.
Cascade controller as standard: The cascade controller connects or disconnects pumps as necessary and according to specified limits. It also enables master/follower operation. Extended functionality is available
Harmonic mitigation: Advanced active filter variants reduce harmonics to below 3% at best, and 12-pulse drives provide robust cost-effective harmonics reduction in supply applications.
EC+ The intelligent VVC+ control principle enables the use of permanent magnet motors or synchronous reluctance motors with efficiency equal to or better than EC technology.
Six reasons why you should choose Danfoss drives
The growth trajectory of the heavy industries has its own challenges. We have highlighted six reasons why choosing Danfoss drives for the heavy industries and harsh environments is advantageous for your organisation.
1) Compact enclosures for reduced infrastructure costs
The highly compact size of Danfoss VLT and VACON drives, designed for the long motor cables, do not require any additional options, which can be installed for smaller switch rooms.
2) Smart heat management systems for significantly lower switch room costs
The technologically advanced back-channel cooling design of Danfoss VLT drives and Danfoss VACON liquid-cooled drives, once installed, significantly lowers the heat load requirement of the switchrooms, ultimately encouraging the usage of compact and economical air conditioning systems.
Danfoss VLT drives feature a high rating of 90+ kW and incorporate a unique back-channel cooling design that includes separate cooling channels intended for the power components and other control electronics partitioned using an IP54 enclosure. The innovative back-channel cooling system helps in removing almost 85% of the power loss using the heatsink and leaves just 15% of the total heat losses to be dissipated in the switchroom.
3) Reliable temperature control system
Danfoss VLT and VACON drives are designed to provide robust performance in the high ambient temperature conditions without any issues related to de-rating when used in harsh environments of heavy industries.
4) Standard extended motor cable capacity
Danfoss AC drives like VLT and VACON drives administer seamless operations. They don't require any additional components as they have a considerable cable length of 500ft for the screened cables and a cable length of 1000 ft for unscreened cables. Furthermore, other output filters are not required for the drive to function reliably with these enhanced cable lengths. This leads to space, installation time, and cost savings compared to the traditional AC drive solutions.
Danfoss HVAC drives feature built-in radio frequency interference (RFI) filters and comply with the EMC standards.
5) Heat load reductions in the switch rooms
The advanced AC drives of Danfoss reduce the heat loss by directly exhausting the heat outside the switch room; this process does not affect the pressurisation inside the switch rooms.
They feature a significantly longer and trouble-free product life cycle that guarantees enhanced asset availability and saves the organisation's maintenance costs.
For the heavy industrial harsh environments, Danfoss drives have electronics coating protection that safeguards the drives in the harsh environment of the heavy industries.
Durga Mechatronics Pvt Ltd, Mumbai.
www.durgamechatronics.com
