G.R.Electronics

When non-linear loads make up more than 30% and less than 80% of the electrical load on a distribution system, some type of harmonic filtering is required to maintain harmonic distortion within the limits. The least complicated filter is a series tuned L-C shunt filter, often called “harmonic tuned filter”. harmonic Such filters are constructed from specially designed reactor (L) and three phase power capacitor(C). One of the characteristic of a series L-C filter is that its impedance is extremely low at the tuning, or resonant, frequency. If we select the tuning frequency to be major harmonic drawn by a non-linear load, the load will only its fundamental frequency current from the distribution system. Most of the selected harmonic current will be drawn from trap filter. Since much of harmonic current demanded by non-linear load now comes from the trap filter and less harmonic current is drawn through distribution system. A series line reactor (Ls) placed ahead of the tuned filter increases the impedance toward the system to harmonic frequencies. The result is diversion of a greater portion of harmonic current to the trap. Harmonic current in the system are further reduced, and the added impedance prevents other harmonic producing loads from over loading the tuned filter. The 5th harmonic tuned filter will absorb significant amount of 7th harmonic current as well. The series impedance will significantly attenuate the higher harmonic frequencies. A harmonic Tuned filter can easily offer guaranteed harmonic current levels, right at the drive / filter input, as low as to 12% THID. The harmonic tuned filter capacity selection is based on the VFD or non-linear load KW/KVA rating. Choose model based on the VFD HP rating or Non-linear load 1KVA = 1HP rating.

We have worked with many OEMs and built a broad knowledge of their product specifications for dynamic braking resistors. You can rely on the industry’s most innovative resistor manufacturer with over 30 years of industry experience. Innovative manufacturing techniques are adapted in our braking resistors to get fail safe feature for VFD protection and offer superior performance. Per kilowatt capacity performance our resistor is equal to 2.4 KW capacity of conventional resistor. There is no need to over sizing resistor capacity for our resistor.

Industrial control equipments demand a momentary overload capacity of three to eight times’ normal capacity. This is most prevalent in solenoid or magnetic contactor applications where inrush currents can be three to eight times as high as normal or holding currents but still maintain normal voltage at these momentary overloaded conditions. General control transformers are designed for good regulation up to 100 percent loading, but their output voltage drop rapidly on momentary overloads of this type making them unsuitable for high inrush application. The current standards require electromagnetic devices to operate reliably at a minimum of 85% of their rated voltage. However contact life may be affected with continuous start-up at that voltage level. Therefore the minimum 90% voltage at momentary loaded condition is preferred for good contact life of electromagnetic devices.

When a capacitor bank is energized, the bank and the network are subjected to transient’s voltage and current. The severity of the effect is determined by the size of the capacitor and the network impendence. The worst case occurs when a capacitor bank is energized close to a bank that is already connected. The inrush current into the newly connected bank is determined by the size of capacitor bank and the inductance between two banks. The larger the banks, and smaller the inductance between banks, the higher will be the inrush current. The frequency of the inrush current is determined by the inrush current is determined by the ratio of capacitor bank reactance and the impedance between the banks. The smaller the impedance, the higher will be the frequency. In most of the installations, the inductance between the banks will be only few micro-Henrys, a peak current of more than 150 times nominal current; at a frequency of more than 8 kHz can be expected. Capacitor standards such as IEC 60871 state that capacitors should be able to withstand inrush currents up to 100 times nominal. The standards suggest a lower value if banks are switched frequently. Large and high frequency inrush current can damage capacitors, circuit breakers and contactors. All connected equipments are subject to voltage transients and may result in sporadic malfunction or failure. To avoid this problem, it is common practice to insert inrush limiting reactors in series with the capacitors.

The accuracy of CT is a function of the magnetic performance of the steel core. Toridally wound cores with high permeability and low loss are used to optimize performance and physical size of the transformers. High grade insulation is used to insulate between the windings and the core and between winding layers. Maximum mechanical and electrical performance is achieved by distributing all windings evenly around the periphery of core.

Harmonic Broad band filters

There has been much discussion and interest in recent years on the subject of power quality. Where as in the past, power received and utilized by an industrial plant was generally a pure sinusoidal wave form – i.e. clean power – most frequently to-day industrial plants have deal with problems of “Dirty Power”. Harmonic distortion is a specific type of Dirty Power that is usually associated with an industrial plants increased use of adjustable speed drives, power supplies and other devices using solid-state switching. Harmonic distortion can cause series operating problems in plant environments.

Line Chokes are modern technology solution for drive application. Protect your drive from harmful line disturbances with GR Line Reactor. GR reactors help to prevent equipment failure and down time and can add years to the life of your Drive.

In long lead application, GR Motor chokes located between the drive and motor help reduce dv/dt and motor terminals peak voltages. The use of the motor choke also helps protect drive from surge currents caused by rapid changes in the load.