A variable voltage D. C. source is required for the Electro deposition process of electroplating, anodizing etc. The various ratings of voltages and currents required for the process depends upon the metal to be deposited and the process adopted. MARSZ Rectifiers are designed in standard voltages of 8 V to 24 V, and in current ratings varying from 100 Amps up to 10000 Amps. Up to 24V DC 10000 Amps for Electroplating and Anodising.
Brief Specification:
A.C. INPUT
Rectifiers are designed to work on 415 V AC 3 ph. 50 Hz. supply and suitable for an input range of 360 V to 460 V AC 3Ph. Units of very small capacities namely 8 V / 12 V / 16 V / 20 V & 24 V DC up to 100 Amps ratings can also be supplied to work on an input voltage of 240 V AC 1 ph. 50Hz. supply.
D.C. Output
The DC output is continuously adjustable from zero to full rated value, from no load to full rated current, over the input range as described. All 3 phase units have low ripple of less than 5% and are suitable for all special processes such as chrome plating or hard chrome plating where low ripple content is necessary.
Circuit and Components
The units are assembled with high quality materials, and the components are manufactured to relevant specifications.
1) MAIN TRANSFORMERS:
The transformers are of class ‘A’ insulation and conform to IS 2026 in general. The laminations used are C.R.G.O Silicon steel, low loss type. The wound coils are impregnated with oven baked varnish.
2) I.P.T:
For high current units the transformers secondary is generally double wye. An I. P. T. wound with copper, is provided on its secondary, to extend the conduction period of windings and diodes.
3) Silicon Rectifier:
The Rectifier is assembled by using silicon diodes, mounted on heat sinks and connected in full wave circuits. Individual R.C. components are used for hole storage protection. The diode assembly is always selected to have at least 40% extra rating above the maximum output current.
4) Regulator:
In order to facilitate voltage variation from zero onwards “VARIVOLT” variable voltage auto transformers are used as independent units, or some times, accommodated in the transformer tank. Motorization is provided as an optional feature.
The DC output is continuously adjustable from zero to full rated value, from no load to full rated current, over the input range as described. All 3 phase units have low ripple of less than 5% and are suitable for all special processes such as chrome plating or hard chrome plating where low ripple content is necessary
Protection & Metering
MCB / MCCB protection is provided on the input and 3 fuses are provided on the output of the “VARIVOLT” variable auto transformer. 3 pilot indicators are incorporated on the incoming side. Digital voltmeter and ammeter with suitable shunts are provided to read the output voltage and currents.
Optional Features
Following optional features can be provided:
- Remote switching-on by using contactors and bimetal over load relays.
- Push button operation by motorization of the “VARIVOLT” variable auto transformer.
- Constant voltage or constant current features using electronic circuits.
- “VARIVOLT” auto transformer with zero start facility.
- Timers, time totalizers, ampere hour meters, etc.
a) Dimmerstat
Output is an important factor in Electrode position processes. MARSZ provide a step less and continuous variation of output voltage, which is a far superior method to other methods of control like resistance boards, tap switches etc. The step less variation is achieved with the help of Dimmerstat’ which is Registered Trade name for Continuously Variable Voltage Auto Transformer manufactured by MARSZ. Unlike other methods of output control, Dimmerstat provides a step less, on-load and without break variation of output Voltage, without any loss of power. It being one of our own standard products, availability of spares or replacement is guaranteed, although the necessity is very rare.
b) H.R.C Fuses
Overloading or short circuiting is not a rare occasion in Electro deposition processes. Special High Rupturing Capacity (H.R.C.) fuses are therefore provided on the primary of the Main transformer. These fuses will blow only when there is overload or short circuit on the output or if there is an internal short circuit and in such cases they should be replaced by H.R.C. fuses of the same rating only.
c) Double Wound Transformer
This is of conventional design and conforms to standard specifications of IS 2026 as regards the temperature rise and insulation are concerned. The primary is delta connected and two secondaries have star connected windings.
d) Interphase Transformer
The IPT is connected between two star points of the secondaries of the main transformer; The Interphase transformer improves commutation thereby increasing the rating of the Rectifier.
e) Rectifier
These is made up of sturdy liberally rated Silicon diodes and are arranged in a six phase circuit. The diodes are mounted on cooling fins so as to dissipate the heat thereby increasing the rating of the diode. Depending upon the output current rating, necessary number of diodes is connected in parallel.
f) Metering
A Voltmeter and an Ammeter are provided on a separate panel to indicate the output voltage and output current. The panel is mounted on one of the tanks to enable easy manipulation with the help of the Dimmerstat. The ammeter is used in conjunction with an external shunt, which is fitted inside the tank.
Construction
The units are made in natural oil immersed construction. Any Electro deposition process is always associated with acidic and corrosive fumes and dust. Any contact with these fumes and dust obviously reduces the life and reliability of the Rectifier. Oil immersed construction offers best protection to the Rectifier unit in this regard and therefore increases the life enormously. The Dimmerstat is always housed in separate tank. For rectifier units up to a maximum output capacity of 100KW, the transformer and the rectifier are housed in one single tank. For higher capacities separate tanks for transformer and rectifier are used. For rectifier units of current rating 5000 amperes and above, the rectifier is supplied in Separate tank for better cooling. If the customer can guarantee that sufficient precaution is taken to see that corrosive fumes and dust do not come in contact with the rectifier unit, we will be pleased to make special offers for units in Air cooled or combined OIL/AIR cooled construction.
Connection
The mains supply is to be connected to the Dimmerstat input terminals by a cable of proper size through a switch fuse unit. The cable of same size should be used for connections from Dimmerstat output to the primary of the transformer.
Note
The Units can also be supplied for remote control or automatic control of output. For remote control, a separate control panel can be provided to operate the motor of the Dimmerstat by means of push buttons & a Voltmeter & Ammeter to indicate the output voltage and current. In case of automatic control the customers are requested to specify the mode of control, whether the requirement is for automatic constant voltage or constant current. These will be at an extra cost which will be quoted against specific requirements. Units of ratings beyond our standard specifications, such as input voltage range, maximum output voltage and current or with overload requirements of short duration can also be quoted against specific enquiries.
