HMT Electronics

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ELECTRICAL ASSEMBLYIt is the main section of HMT electric departments. There are departments. preparing the panel board for the various machines which are used in various operations they are mostly grinder machine and lathe machine panel prepare. prepare. All the controls and relaying mostly for the panels of the machine such as Push Button Contactor Thermal over load relay Timer Miniature circuit Breaker Fuses & limit Switches. Switches. Starters

PUSH BUTTONA push button is a device that provides control of an equivalent by pressing button. A push button button. is shown in figure. The contacts are operated by a figure. button. button. Two sets of contact, one is normally open [N/O] and normally closed [N/C] are provided in a push button. When the push button is pressed by button. applying a force, the N/C contact opens and N/O contact closed. The push button stays in its closed. depressed condition as long as it is held pressed. pressed. When the pressure on the push button is released, a spring inside the push button brings the contracts back to their initial positions. positions.COLOUR CODING OF PUSH BUTTON Colour Red Green Yellow Operation Stop or Off Start or On Intervention

CONTACTORSA contactor is a mechanical switching device having one position of rest corresponding to the position of the main contacts either open or closed operated otherwise than by hand, capable of making, carrying and over load condition the speed of make and break being independent of the operator. operator. There are various types of contactors available. available. They are electromagnetic contactors, pneumatic contactors, electro pneumatic contactors, latched contactors etc. The detail of etc. an electro magnetic contactor given below. below. ELECTROMAGNETIC CONTRACTOR Construction - Is has got a coil which is to be connected across a voltage according to its rating. rating. It will have contracts normally open [N/O] and some normally closed [N/C]. [N/C].

Over load relayOverload relay is to be used in control circuits for protection purpose against over load. load. It this relay a bimetallic strip is provided. provided. A heating coil is wound on the strip, which carries the line current of the circuit. circuit. In case of over load current flowing through the coil the bimetal bends considerably and opens a normally open contact or close a normally open contact as shown in fig. The fig. opening or closing of the contact of the relay during overload can be utilized in tripping off the circuit in which this relay has been employed. employed.

TIMERTimer are the electrical components used for setting the time in which contacts get changed. It is used for connection convert into star-delta depending on the timer rating breaking time period setting. It is use for the protection of the machine. It is used in interlocking CKL.

These are two type of timers 1. Electronic Timer 2. Electro pneumatic timer

MINIATURE CIRCUIT BREAKERMiniature circuit breaker consists of a contact in series with over load thermal coil which mechanically causes the opening of contact to isolate the faculty circuit. In some of the MCB'S circuit. auxiliary contacts for initiating a remote alarm of visual induction is provided. provided.

Fuse and MCB's are is fact used to isolate a system from the supply in case of Over load Short circuit Under voltage

FUSESA fuse is an over current protective device with a circuit opening fusible member which may be a thin wire or a trip directly heated or destroyed by the current passing through it. it. The thin wire on strip is placed in series with the circuit to be protected. protected.

Fuses are of two types:1. Rewirable fuse 2. Cartridge fuse.

LIMIT SWITCHESA limit switch is a mechanically operated device, the prime function of which us to open or closed a contact in a circuit when a certain limit, physical distance covered by a device operated by a motor has been reached. reached.

A limit switch is either stationary and actuated by some moving member or it moves with the machine and is actuated by a stationary member. A limit switch usually will have one normally open and normally closed contact.

C.N.C. MACHINESCNC (Computer Numerically Controlled) work on binary system Machining centre: A machine centre: which capable to performing multiple operations on a work piece in a single set up like milling, drilling, boring and tapping. tapping. Main parts of CNC Machine Center Bed Saddle Column Table Servomotor Ballscrew Spindle Tool Changer And Machine Control Unit

ADVANTAGES OF C.N.C. MACHINES Higher flexibility Increase productivity Consistent quality Higher accuracy Less rejection Reliable operations Reduce scrap rate Shorter cycle time Automatic tool change Lesser floor space Complex machining operating Greater machine utilization Tooling cost reduced (Jig &


Reduce non-productive time Increase operational safety Reduce manpower

MAINTENANCE AND REPAIR SHOPWINDING SECTIONIt is the main section of HMT where the maintenances and repair of A.C. and D.C. machine winding is made by workers. workers. Different types of machines came here for repairing, maintenance and rewinding. Which are as follows. rewinding. follows. A. C. Induction motor. motor. A. C. slip ring squirrel cage motor Universal Motor Transformer. Transformer.


In induction motor has two types. Squirrel cage induction motor. Slip ring induction motor. An induction motor consists essentially of main two parts. Stator. Rotor.

STATOR & ROTORStator is a stationary part of an induction motor. motor. It is cylindrical structure built up of dynamo grad laminations. laminations. The laminations are either 0.35 or 0.50 MM thick. Stator carries a three-phase wdg and is thick. threeperform a 3-phase supply. It is wound for a definite supply. number of pales, the exact no. Of poles being no. determined by the requirement of speed. Greater speed. the no. Of poles, lesser the speed and vise versa. no. versa. When three phase supply given to the stator wdg. It wdg. produces a magnetic flux which is of constant magnitude but which rotates at synchronous speed. speed. This revolving magnetic flux induced an e.m.f. In the rotor by mutual inductance. inductance. motor. Rotor is the rotating part of induction motor. Various types of rotor are used in the Induction motor such as Squirrel cage induction motor. motor. Double squirrel cage induction motor. motor. Phase wound Rotor

SLIP RING MOTORStarting torque of these motor are better than squirrel cage motors when we drives these motors the starting condition high resistance wedgs of motor are used but after coming in its synchronous speed then only works low resistance wdg. The slip wdg. ring motors are used where high starting torque is required. For required. Instance In the hoist For lift In the crane For Power Hammer For battle ship purpose The squirrel cage motor is not useful where the motor has to start against heavy load. load.

MOTOR WINDINGThere are four main points: 1. No of slots 2. No of pitch 3. No of turns 4. Gauge of wire Winding material:material:1. Conducting material 2. Insulating material 3. Solder & flux

ARMATURE WINDING FAULTSThere are three faults in armature winding: winding: SHORT CIRCUIT FAULT: When the leads of armature coil FAULT: touches each other electrically, it is called short ckt fault. fault. OPEN CIRCUIT FAULT: When the leads of the armature coil are FAULT: released commutator segment in breakdown position called open circuit fault. fault. EARTH FAULT:- When coil or coil lead or commutator segment FAULT: touches the body of rotor, it causes the earth fault. fault. TESTING METHOD OF ARMATURE 1.Series test lamp method 2.Growler testing method 3.Genral method of testing

FAN WINDINGIt has two winding one in inner side and other is or second is in outer side and is called running and starting wdg respectively. respectively. Starting winding have more turns on coil comparative to running wdg. wdg. Due to increase its starting resistance. Each coil are wounded resistance. in opposite direction or we can say that, these coils are wounded first in clock wise and then anti clock wise. wise. Generally super enameled copper of 33 and 35 S.W.G. are used in fan wdg. Four wires or terminal are taken out from starting wdg. and running winding. winding. According to the circuit, a capacitor is connected to the starting winding to start the motor so this motor is called capacitor start motor. motor. Exchange is provided where is water cold angse waste is utilize to cool the refrigerants from the condenser coil before entry to drier. drier.

SUBSUB-STATIONThe Sub Station is an assembly of apparatus which is used to transfer of electric supply, is called an sub station. station. HMT sub station is situated at Beawer Road, Ajmer. It is a Ajmer. source of electrical energy for HMT Machine Tools Ltd. HMT Ltd. Township and general stores. stores. Power house is basically a 33/11 K.V. S/S and its line dia 33KV 33/ 33KV feeders have come here one is from RSEB Madar by crossing Nasirabad road and other one is from RSEB Saradhana by crossing national hiway No. 8 No. Different safety equipment and precautions are arranged in these feeders, which are already shown in diagram. These feeders diagram. are coming at AVVNL Grid sub station .At a time only one feeder can be use. use. In the HMTS sub station the 11 kV supply is step down to 440 volt & then distributed to various sections of HMT factory & town ship

CLASSIFICATION OF TRANSFORMER SUB STATIONThe majority of the sub station in the power system are concerned with the changing of voltage level of electric sup