TRANSFORMERS.

 

 

 

   Transformers for furnace duty are frequently subject to electrode/ element short circuits and the mml length and the leakage path designs have to be taken care. Moreover the control of heating can be effected in multiple ways, viz. switch control, variac control, transductor control and antiparallel thyristor control. The transformer design has to take into account of the type of control and the type of furnace as a normal double wound transformer will fail prematurely or force the user to underutilize the unit.

 

   PPT has the know-how and the ability to manufacture ideal furnace transformers may it be dry type or ON type. The range of manufacture includes up to 800 kVA or 5000 Amps for typical salt bath applications

 

 

 

 PPT makes annealing transformers for nonferrous metal industries with a collaborator for annealing controls. The design feature requires meticulous control over impedance features and eddy losses, apart from control of mml parameters. The currents range from 5000 amps to 30000 amps depending on metal, diameter, feed duty cycle etc. A large number of such systems have been successfully supplied and commissioned in India and Overseas.

 

The vector grouping and phase configuration of such transformers again depend upon the type of controller employed viz. variable torque, vector control, constant torque.

 

 

 

Despite the unbalanced currents and harmonic distortions there is much use for these phase conversion transformers by means of open delta, scott, le-blanc, or tee configurations when the power has to be derived from a three phase 120deg phase shifted nodes.

 

Type of application, output voltage, current, control, system impedance shall be the guidance for the best suited alternative. The leakage impedance shall be the first and foremost limitation apart from winding displacements and balancing the counter emfs are some of the areas that require the kind of expertise that PPT has.

 

The range of manufacture includes up to 800 kVA for furnace, 250kVA for computer centre and power centre applications.

 

 

Phase in phase and phase out applications like in vector control applications require a 60 deg in and out phase shifting of the limb phases resulting in zigzag vector outputs. Careful distribution of leakage path and flux route apart from optimum utilization of core and copper are the challenges that require to be addressed. If the neutral is not properly located would result in a circulating one.

 

Hexaphase transformers with 120 deg input and 60 deg outputs with 6 phases are common requirement for low voltage high current rectifier systems and for laboratory applications. Interphasing transformers shall also be supplied along. The range of manufacture includes up to 1 MVA ratings of wound components.

 

 

 

When the incoming lines induce electromagnetic interference and noise into the equipment circuitry, erratic behaviour of system and supporting auxiliaries result in heavy losses. To overcome this it is essential for one to de link sensitive instruments and systems like instruments, plotters, c cores, PLCs, recorders, line computers and other interlinked wares from the regular mains through isolation transformers.

 

These transformers in turn include coupling capacitance which again has to be restricted to avoid transmitted transients. Effective multiple shielding is essential and the disturbances have to be passed on to the ground. Dedicated earthing is a must for such applications.

 

A complete description of such emi and transients and means of preventing them are discussed elaborately in individual product catalogues

 

PPT make isolation transformers cover ratings up to 20 kVA in single phase and 100 kVA in three phase.

 

 

In high voltage low current applications PPT product range covers up to 200kV in oil cooled construction. These transformers are used in specific applications for firing, ignition and electron beam welding rectifiers. Typically, a neon sign or an ignition transformer has to be made with a leakage circuit so as to limit the short circuit current to milli amperes with the full system input. PPT makes such transformers in bulk quantities for 6.6, 10, 12, 15, 20 and 30kV classes.

 

High current injection sets and high current transformers find varied applications, right from test shops to melting shops. Wood processing industries require special type of high current transformers whereas high voltage ones are required for glass factories. PPT caters to all such specific requirements of low voltage high current applications covering up to 40000 amperes.

 

 

Wherever 3 wire supplies are drawn from HT and a neutral is required for distribution of single phase and lighting load lighting transformers are a must to provide isolation as well as a power neutral. The power neutral has to be maintained at zero phase with reference to earth and the vector grouping is chosen as per synchronizing sequence viz. Dyn1, Dyn11 etc. The ratings generally demanded are within 400 kVA range.

 

PPT also manufactures special purpose lighting transformers for Runway lighting, Swimming pool lighting etc in single phase configuration.

 

 

 

 

General purpose transformers handle sinusoidal AC in most of the cases in both the input and output windings. However when it comes to transformers supplying rectifier UPS loads in the secondary sides the input and output waveforms differ. For example a square wave in

the secondary will induce a power factor between the input voltage and current. Similarly all root mean square temperature factors of windings will get disturbed. The input power (rms) and the output power of the transformation may not equalize as in some cases like a CT circuit or a hexa phase circuit - where the current does not flow through the full portion of the windings all the time due to instantaneous differences and form factor modulations.

 

While making such transformers one tends to over design things as a safety measure. At the same time enough care has to be taken for providing for extra super imposition fluxes in the core paths also.

 

PPT supplies any kind of rectifier transformers once the parameters are given to them. Either total rectifier unit is supplied or only the transformer part with suitable coordination for the entire system.

 

 

CVTs as they are called are the best sources for stabilized voltage except that there comes few unwanted limitations along like harmonics, noise, minimum conditional load, higher size and costs, unsuitability for inductive or capacitive loads etc. Apart from the above in the positive side none can match the speed of correction of a CVT, and once properly made it is a maintenance free unit as there is no moving part (proper sealing of shunt path a must). It covers a wide range of fluctuation.

 

PPT undertakes to make single and three phase CVTs in bulk quantities up to 10 kVA ratings.

 

 

Last but not the least PPT make control transformers have a no fail history and the transformers are available for panel builders right from 50VA to 10 kVA.

One of our esteemed customers uses almost 30 to 50 such transformers once in 2/3 days in his cable relay network because of the fail proof history.

 

The quality is matching international standards and the design is very adaptable for panel builders.