Frequently Asked Questions

How is Auto-Plot facility useful?

The Auto-Plot facility enables the students to generate textbook V-I characteristic waveforms for the target power devices at the press of a button. This facility confirms the students about working of the target device and motivates them to study the intricacies of the device characteristics. Since the measurement readings of these Auto-Plot graphs are not available to the students, they are expected to re-create them manually to improve their understanding.

When testing any external device, the Auto-Plot facility is useful to understand the characteristics of the target device without any difficulty and motivates the students to apply the device in their applications with confidence.

Why is a constant-current power supply essential to take up the study of SCR and TRIAC?

Theoretically, SCR and TRIAC are current triggered devices and a constant-current power supply is very much required to maintain gate current at a constant value when the anode-cathode voltage is being varied. If a simple voltage power supply is used for this purpose, the gate current will vary every time the anode-cathode voltage is changed. The students have to adjust the gate current to the set value for every change of anode voltage and this may cause an inadvertent triggering of the device. Students may miss the exact triggering points which may become disadvantageous when designing control algorithms for these devices in their applications. Without constant-current gate power supplies, plotting the accurate characteristic graphs of SCR and TRIAC is very much difficult.

What is the significance of the current waveforms in power electronics application study?

During the study of Buck and Boost Converters, the current waveforms of the inductor and the switches are essential to understand the circuits in continuous and discontinuous modes of operations. High frequency current probes are very expensive and difficult to use. FE’s trainers have on-board current measurement facility to enable the students view current waveforms which can otherwise be seen only in the textbooks.

What are the advantages of the built-in oscilloscope over external oscilloscopes?

The built-in two channel oscilloscopes of FE’s application trainers are designed for precision and convenience rather than regular oscilloscopes which are built for speed. The in-built oscilloscope supports 12-bit resolution, differential voltage and current measurements enabling students view two voltage/current waveforms simultaneously. The oscilloscopes also come with mathematical functions like Peak-Peak, RMS, Mean, Minimum and Maximum on the acquired waveforms. External oscilloscopes are not capable of differential voltage measurements or high frequency current measurements without expensive active probes.

Why high precision measurements and power sources are required?

In the device characteristics study, the range of gate voltages and currents required for making the device operate in active region for V-I characteristics study is very small: around 200mV to 300mV for MOSFETs/IGBTs and around 50µA to 100µA for SCRs/TRIACs. Without precision power supplies and measuring facilities, obtaining multiple V-I characteristics plots is out of question.

In power electronics application study, precision measurement facility is required to cross-verify theoretical design calculations with practical results. The 12-bit in-built oscilloscope is more suitable for measuring mathematical parameters of current and voltage waveforms than an external 8-bit DSO. This is particularly significant for buck and boost converter designs where parameters like inductor ripple current, average inductor current and output voltage ripple are to be measured.

When using FE trainers, won’t the students miss out on the assembly and troubleshooting skills that come with breadboard or other assembly options?

Study of power electronic device characteristics requires high precision power supplies along with multiple multimeters for every experimental setup. The cost of the equipment and the difficulty in maintaining them, especially, the µA current range multimeters/ammeters which tend to be damaged very easily, is prohibitive for most college labs. Usually, compromises are made during experimentation and the students have to set up the study with only available low-end T&M equipment which defeats the learning process.

For the application experiments, a complete study requires complicated circuitry which cannot be assembled in the breadboards or DIY boards in reasonable time. So, advanced triggering/control circuits cannot be studied during the lab sessions. Also, the students cannot make differential voltage or current measurements with external oscilloscopes unless extremely expensive active probes are made available to them. When students have more time for learning, FE trainers support them with more options in load, triggering, applying different passive devices to continue their study that result in enhanced learning.

Moreover, with manual breadboard assembly, the students have to spend significant time in assembling and troubleshooting the circuits that leaves very little time for the required learning. There are other electronic labs where the students can learn about electronic assembly and troubleshooting. But, for the power electronics lab, the students are at the risk of missing out on the key concepts which may prevent them from exploring further in power electronics.

As a whole, FE trainers provide an ideal learning environment to the students which boosts acquired knowledge, more than expected in power electronic study in any lab.

What makes FE power electronic trainers better than other options with low integration?

Besides the Auto-Plot and constant-current power supply features, FE Power Device Characteristics Trainers also have high precision digitally controlled power supplies along with on-board high precision 3.5 digit resolution current and voltage meters.

FE Power Electronics Application Trainers have built-in two-channel high-resolution differential oscilloscope with voltage/current measurement and mathematical calculation facility. The application circuitry is modular and user-configurable with multiple triggering/controlling and passive device options.

Everything is integrated into a single stand-alone solution with a convenient and intuitive user-interface using a TFT colour LCD combined with professional rotary encoders and switches. The circuitry is given adequate protection against inadvertent mis-wiring and shorts, giving long working life with zero maintenance.

Simple trainers with low integration do not have any of the above mentioned advanced features and only provide analog power supplies with or without low precision analog or digital voltmeters/ammeters for characteristics study and simple circuitry with limited triggering options for application study. They do not provide any significantly better learning than manual breadboard assembly. This discourages the student from getting a thorough learning in power electronics; missing confidence to apply these devices in further applications.

Astronomical Timer

The astronomical timer enables switching on and off of lighting loads at precise sunrise and sunset timings for geographical locations. Latitude and Longitude information is entered by using DIP switch settings and the information is programmed for all the cities in India (Data for other countries can be added as per user requirements). A high accuracy RTC is used along with battery backup to maintain timing.
DIP Settings:
DIP 1: Off Time Selection
DIP 2: State Selection
DIP 3: City Selection
Technical Specs:
Operating Voltage: 230V AC Single Phase
Clock Accuracy: ±0.5 sec/day
Battery Backup: >5 Years with Lithium Battery (used only in absence of AC power)
LED Indication: Red Coloured Status LED
Relay Contact Type: 1 Normally Open SPST Contact
Relay Contact Rating: 16A
DIN Rail/Panel Mountable Enclosure

Astronomical Timer controls time based operations without using any sensors and they are most suitable for the lighting applications. Any alternate solutions using sensors tend to fail in due course of time because of accumulation of dirt over the sensor. The timer operates as stand alone and assures a trouble-free operation for a very long time.

Earth Fault Indicator

The Earth Fault Indicator (EFI) is a equipment that measures the Earth Fault Current in a 11kV transmission system by using a Split-Core Current Transformer and raises an alarm when the current is over a preset limit. The EFI has Isolated I/O contacts suitable for connection to the SCADA system via Field/Remote Terminal Units. The EFI is powered by a single Lithium Battery and is of Ultra Low Power Design to ensure a battery life of 10+years.

The EFI has two components; the Detection and Signalling unit and the Current Transformer:

The Detection and Signalling unit is a stand-alone battery powered system which monitors the signals from the current transformer and triggers an alarm if the value exceeds a set limit. The unit gives visual indication with a high powered LED which is visible for long distances even in daylight. The triggered alarm can be reset manually using a push-button, through signals from a SCADA connected terminal unit or automatically after the elapse of a set timing. The EFI has user configurable settings for Trip Current Value, Trip Current Duration, Alarm Auto-reset time and 230V AC sensing.

The Current Transformer (CT) is a Core-Balance type Split-core current transformer with suitable insulation that can be easily mounted over 11kV cables without need for breaking the line. The CT is suitable for outdoor operation and can withstand being submerged in water for prolonged periods of time. The CT is designed to saturate during heavy earth faults to protect the EFI from damage. The Current rating and diameter of the CT can be modified as per customer requirements.


Field Terminal Unit

The Field Terminal Unit (FTU) is a Miniature RTU System used for monitoring and control of Earth Fault Indicators, Circuit Breakers and Relays in Distribution Sub-stations to assist in fault locating, sectionalizing and restoring of the power supply.

The FTU communicates to the Master SCADA System via a GSM Modem and relays the input status data in real-time. The FTU also accepts the control signals from the SCADA System for the outputs and reflects the same in real time.

The FTU is of modular design to enable easy maintenance and upgradability. All the Modules are Mounted on standard 35mm DIN rails inside a rugged IP54 Certified Metal Panel suitable for Outdoor Installation in Hot Tropical Climate.

FE exports FTUs to eastern countries from 2016 onwards.

FE already delivered a few thousands of these FTUs. Here, you can see a batch of FTUs ready for pick up at our office.

FTUs were ready for pick up.
Study of Power Electronic Devices in Applications

Study of Power Electronic Devices in Applications

FE has a line of trainers enabling students understand how power electronic devices are put into selected applications. Trainers include modular circuitry with multiple controlling/triggering options guiding students’ experiments with multiple design concepts in the applications to ensure maximum learning in the given time. The trainers come with multiple triggering choices, multiple loads, multiple passive component options to enhance the knowledge acquired.

The trainers are complete in all respects and they can be used as a stand-alone experimental environment without requiring any other external T&M support. They come with built-in two channel differential oscilloscope features required to view and measure all the voltages and currents at the important locations to get a thorough understanding of the design concepts in the most convenient way. On-board TFT colour LCD and professional encoders provide an unmatched study interaction to the students. Mathematical measurement facilities like finding Peak-to-Peak, RMS, Mean, Maximum and Minimum are available to understand more on target signals. The oscilloscope function supports two simultaneous floating measurements through differential input sensing facilities.

The scope functions have high resolution measurements with 12-bit capability as opposed to common oscilloscopes of 8-bit resolution, resulting in high resolution and accurate measurement on the input signals during the study.

The trainer’s application circuitry is designed to protect the target device in case of any inadvertent shorts, mis-wiring by the students. Total design is optimised for college lab environment and is designed to provide a long working life with zero maintenance.