Sterling Controls Pvt. Ltd. Lower Parel, Mumbai, Maharashtra

Resistance Boxes Manufacturer are assembled with stainless steel wire grid type or punched stainless steel type elements, which are restless, unbreakable, and capable of withstanding mechanical shocks and vibration. The grids are mounted on high tensile steel rods insulated with heat resistant Mica tubes. These assemblies are mounted in well ventilated sheet steel housings, ensuring low temperature rise. All Resistance steps are terminated on a common terminal strip which facilitates installation and wiring.

A guide to the application and selection of sterling shoe type brakes It is often essential for safety, control or convenience that a machine driven by an electrical motor should be stopped,slowed or held stationary against gravity or other forces. In most cases, because of the need to apply the brake automatically in the case of power failure or other interruption, these brakes are normally of the `FAIL-SAFE’ type. Fail-Safe type brakes are usually applied by means of springs or in some cases by dead weights. The brake release is in most cases electrical and when power is applied the electrical actuator releases the brake and the motor on which the brake is fitted is free to run at it’s normal rated speed. The simplest and most effective control is achieved by connecting the brake and motor in parallel so that the brake is released while the motor is running and applies as soon as power to the motor is cut off. In practice the brake is connected across 2 or 3 of the supply terminals of the motor which the brake is controlling, dependent on the brake release actuator being used. Satisfactory operation of the braking system requires correct selection of the brake type and size, and this selection is dependent on the application, duty cycle and some characteristics of the drive and it’s components. STERLING shoe type brakes usually operate either on a flexible brake drum coupling connecting the motor to the gearbox or other drive component or on a brake drum fitted on the non-drive end of the motor or the input shaft extension of the gearbox if available. The brake shoes, lined with friction material, clamp the drum under the influence of pressure from the compression springs and release evenly when the electro-magnetic solenoid, thrustor, pneumatic cylinder or other actuator is energized. STERLING Brakes are used on almost any type of motor driven equipment where controlled stopping, slowing or holding of the drive motor is desired. Some of the common machines on which brakes are used are : Roll Former’s,Calendars, Conveyors, Extractors, Centrifuges, Screw Feeders, Granulates, Cranes and Hoists, Coil Winders, Rubber Mixing Mills, Baling Presses, Large Machine Tools, Steel Rolling Mill Stands, Coolers,Uncool and several other types of industrial drives. In various applications the exact requirements are dependent on the use. Some users may require to stop the motor by plugging and holding the motor stationary against a load, while other requirements may call for the use of a brake for both the same functions. Some requirements call for the use of brakes for positioning of driven machinery while others Require brakes for safety or for preventing damage to driven machinery in the event of a power failure or other interruption. STERLING can provide brakes for almost any requirement. We manufacture a variety of brakes of different type and while all brakes would stop a given motor, each type has different characteristics, specifications and prices and actual selection would depend on the user’s particular requirements. Our range of brakes has the following categories: Single Phase AC Electro-Magnetic Brakes  [PRODUCT CODE 10] Hydraulic and Mechanical Manual Brakes   [PRODUCT CODE 11] Three Phase AC Electro-Magnetic Brakes    [PRODUCT CODE 13] Electro – Hydraulic Thrustor Brakes              [PRODUCT CODE 14] Thrustor Operated Creep Speed Brakes       [PRODUCT CODE 15] D. C. Electro-Magnetic Brakes                       [PRODUCT CODE 16 & 17] Pneumatic (Or Hydraulic) Powered Brakes   [PRODUCT CODE 19] STERLING SINGLE PHASE ELECTRO-MAGNETIC BRAKES [PRODUCT CODE 10] Features very fast application and release, and suitable for unto 120 or 240 operations per hour depending on the coil rating. Higher operating rates are permissible for short time intermittent operation but mechanical life is limited due to constant impact of the magnet lamination. Standard brakes are supplied with coils wound to accept a 415 VAC, 50 Hz. 2 Phase supply allowing the brake to be connected across two of the three terminals of the motor it is connected to. Other voltages are available as Ideal for low cost, light duty applications. Requires regular maintenance and periodical replacement of worn parts and coils. STERLING HYDRAULIC AND MECHANICAL MANUAL BRAKE [PRODUCT CODE 11] These manual brakes are used to supplement the electro-mechanical brakes mainly to provide operator controlled braking in addition to the automatic braking action and allow the operator extra control on slow motor speeds to cater for variations in load. These brakes are normally reverse acting, non-fail-safe types where the brakes are spring released and manually applied similar to the braking action of automobile. Two systems are available with the control being hydraulic in one case and purely mechanical in the other. The hydraulic system involves a foot pedal operated master cylinder on the operator side and a slave cylinder in the brake inter-connected with tubing while the mechanical system involves mechanical linkages such as wire ropes etc. between the operator and the brake. The former allows more precise control and causes less operator fatigue. STERLING THREE PHASE AC ELECTRO-MAGNETIC BRAKES [PRODUCT CODE 13] Similar  in  principle  of  operation to the single phase AC electro-magnetic brakes, these brakes  have  a  more  rigid construction  and a better designed and more efficient solenoid, with damping provided to cushion lamination impact  and thereby  extend  solenoid life and provide a smoother braking action.   These brakes have a better duty cycle than the single phase brakes and are supplied for a standard supply of 415/440 VAC, 3 Phase, 50 Hz.  Other voltages are available. STERLING THRUSTOR OPERATED BRAKES [PRODUCT CODE 14] Smooth, quiet, efficient and reliable braking action with high duty cycle capability is the main features of these brakes with the actuator being a THRUSTOR, a self contained device where the rotary action of an electric motor is converted into linear action by hydraulics to release the brake. These brakes are suited for the most arduous duty conditions and require little, if any, maintenance for extended periods of time. The Thruster is virtually unaffected by any overloading and its smooth braking action results in low lining wear and less strain on the motor or driven equipment. Constructed from fabricated steel these brakes are heavy duty and suitable for more than 700 operations per hour (depending on size of brake and thruster) they operate of a standard 415/440 VAC, 3 Phase, 50 Hz. supply. STERLING CREEP SPEED THRUSTOR BRAKES [PRODUCT CODE 15] The STERCREEP Braking system is used where braking for very low speeds and/or inching operations are required with greater control and efficiency than normal braking can deliver and allows a slip-ring (wound-rotor) motor to `creep’ at low speeds with partial braking action from a thrustor brake and this control is produced due to variation of the thrustor  motor speed in direct proportion to the main motor shaft speed. Usually used in conjunction with another thrustor brake on the same drive.Supplied with an auxiliary control panel which selects between creep speeds and normal running speeds. STERLING D.C. ELECTRO-MAGNETIC BRAKES [PRODUCT CODE 16] Fast acting, reliable and high duty cycle capability are the main features of this type of brake which has traditionally found applications in the most arduous applications not only with D.C. equipment but also with A.C. equipment with suitable voltage conversion controls. STERLING PNEUMATIC (OR HYDRAULIC) POWERED BRAKES [PRODUCT CODE 19] These brakes are ideally suited for locations where pneumatically operated controls are desired and also for places having a hazardous environment where such equipment is desired. These brakes can be supplied for almost any plant air supply and all necessary pneumatic line accessories such as filters, lubricators, solenoid valves etc are normally supplied with the brake, constructed from fabricated steel these brakes are suited for heavy duty application and are quick acting and efficient. Solenoid valves can be supplied for most voltages enabling such brakes to be used in mobile applications. Similar brakes can be supplied with hydraulic actuators instead of pneumatic actuators if hydraulic lines are available instead of pneumatic lines and if so preferred. SELECTION CRITERIA The simplest way of selecting a brake is to select a brake having a retarding torque, or braking torque, equivalent to the Motor Full Load Torque. It is reasonable to assume that this retarding torque will bring the motor to rest in the same, or less, time than the motor takes to run unto it’s full rated speed. This torque can be determined by the motor HP or KW rating and the speed of its shaft. This torque can be calculated using one of the following formula : 720 X H.P             973 X K.W ——————  OR  ———————  = TORQUE IN KG/M R P M                      R P M Once this torque is determined, selection of a suitable brake of any type can be made for a given particular application and duty requirement. However the following guidelines should be followed wherever applicable: (1) In certain cases where the driven equipment has high inertia’s or where safety and/or overload margins are desired, the additional braking torque required should be taken into consideration while selecting the brake. (2)The greater the duty cycle, or number of operations in any given period, the larger the diameter of the brake drum size should be selected for any given torque, as 85% of the heat generated in stopping the motor is dissipated  through the brake drum and a larger surface area ensures better cooling and less lining wear. (3) If the motor is electrically broken by plugging or dynamic braking, the torque requirements remain the same for emergency stopping but a smaller drum size may be selected due to considerably reduced heat generation. RECOMMENDATIONS For certain equipment the following guidelines are recommended: (A)   CRANES , LIFTS, WINCHES, HOISTS: Hoist Motion: The brake selected must be capable of the equivalent overload that the hoist on which it is used is designed and tested for. Example:  if the hoist drive is designed, and tested to 150% of rated load the brake must be selected for at least 150% of the motor full load torque.] Most DC and AC electromagnetic and industrial brakes manufacturers and users of such equipment use brakes with a torque rating of 150% – 175% of motor full load torque. Travel Motions: On travel motions the requirements are usually 100% for cross travel and 75% – 100%  for  long travel motions. (B)   STEEL ROLLING MILLS: 100%  Braking  torque  is recommended for Main Mill Motors, and 40% – 60% torque  for  coilers  and  uncoilers  handling metal strips. (C)   CONVEYOR DRIVES: The braking torque recommended is usually 75% – 100% of motor full load torque. However with conveyors it is normally inadvisable to stop the load too quickly as the load may slip on the belt or may cause the belt to stretch or tear. Delayed braking is often used and prevents the brake from being applied until the conveyor has slowed down. In such cases the holding torque required may be as low as 20%. Inclined conveyors require special calculations and special anti-rollback brakes are often required especially in such drives where a fluid coupling is used to couple the motor to the drive. STERLING offer special anti-rollback brakes for such applications.

Two Way Series Limit Switch is used to prevent over travel or over traverse. The Limit Switch is fitted with 2 sets of contacts which remain normally closed and supply power directly to the 2 phases of Motor in either direction. When the lever is moved over a projecting member fixed at a pre-Determined position on either side of the gantry, the power supply to the motor is cut off. The contacts are automatically reset when the lever returns to `Zero’ position due to spring action. The contacts are rated for 60 Amps at 415 Volts A. C. 50 cycles supply system.The side covers are of cast iron. The top and bottom covers are of sheet steel. The lever is of Mild Steel fitted with M. S. Roller.

“STERLING” Grid type Resistance Boxes are usually used with slip-ring [Wound Rotor] Motors [AC and DC] to provide control of starting torque, starting current and speed. They are designed to meet different classes of service, in various applications where slip-ring motors are used such as Conveyors, Screws Feeders, Steel Rolling Mills, Rubber Mills, Cranes, Hallagues, and Compressors etc. Desired control operation of Slip-ring Motors is obtained through external connections of appropriate values of Resistance into the Rotor slip-ring circuits. Slip-ring [Wound Rotor] Motors can operate with an infinite number of different speed, torque or current characteristics. Different performance criteria are obtained by the selection of external resistance which is connected into the slip-Ring circuit. “STERLING” Grid type Resistors are custom designed and manufactured to suit customers specific requirements, whether for starting duty or for continuous-speed-duty operations, in accordance with relevant BSS, NEMA or IS specifications. Rating / Duty Cycle  The Resistances are designed and manufactured to suit rating and duty cycles as required by the customer in his application and temperature rise does not exceed the limit specified in BSS 587-1957. Operation “STERLING” Resistances may be operated through Drum Controllers or by Master Controllers with associated contractor gear or with Timers and contractors in Slip-ring Motor starter panels. Construction “STERLING” Resistance Boxes Manufacturer are assembled with stainless steel wire grid type or punched stainless steel type elements, which are restless, unbreakable, and capable of withstanding mechanical shocks and vibration. The grids are mounted on high tensile steel rods insulated with heat resistant Mica tubes. These assemblies are mounted in well ventilated sheet steel housings, ensuring low temperature rise. All Resistance steps are terminated on a common terminal strip which facilitates installation and wiring. Ordering Information While ordering STERLING Resistance Boxes the following information is requested which will enable us to provide you with the most suitable offer? 1. Application details 2. Supply: AC/DC 3. Motor HP/KW 4. Rotor Voltage and Rotor Current 5. Starting Torque required 6. Number of steps required 7. Whether operated through Drum Controller or Master Controller / Contractors 8. Any other specific requirements OTHER PRODUCTS Flexible Brake Drum & Brake Drum Couplings. Full Geared & Half Geared Couplings. Geared Brake Drum Couplings. Carbon Brushes Punched Grids Spare Coils for EM Brakes. Brake Liners & Brake Shoes. Cable Carriers & Trolleys. Clutches & Disc Brakes Current Collectors & Spares  “STERLING” Engineers will be pleased to assist in the selection of this item in special requirements and applications.

These brakes are ideally suited for locations where pneumatically operated controls are desired and also for places having a hazardous environment where such equipment is necessary. These brakes are constructed from fabricated steel and are suited for heavy duty applications. They are quick acting and efficient. Solenoid valves can be supplied for most voltages enabling such brake to be used in mobile applications. Similar brakes can be supplied with hydraulic actuators instead of pneumatic actuators if hydraulic lines are available instead for pneumatic lines and if so preferred.

“STERLING” Master Controllers are vertical mounting cam operated sequence switches for use in conjunction with contactor equipment These controllers have been specially developed for frequent operation under the most severe conditions. They are suitable for most Motor drives such as Rolling Mills, Cranes and other applications demanding frequent operation and trouble   free service with limited time available for routine maintenance. We sterling controllers like many other Manufacturers of Master controllers which are exceptionally light in operation with consequent reduction in operational failure. The contact is a single integral unit and independent of the main cam shaft. The contact tips are bimetallic and can be replaced without disturbing any connections. The entire contact assembly is secured by 2 screws only and it can be removed easily to facilitate maintenance/replacement. ENCLOSURES: These Controllers have sheet steel enclosures and are wall fixing as standard. Special mounts can be provided to suit customer’s specific requirements. Operation: Operation is by Ball handle and normally provided with spring return. Operating sequences are standard and special sequence can be catered for. The number of steps and cams can be varied to suit customer’s requirements.

Two Way Series Limit Switch: “STERLING” Two Way Series Limit Switch is used to prevent over travel or over traverse. The Limit  Switch is fitted with 2 sets of  contacts which remain normally closed  and supply power directly to the 2 phases of Motor in either direction. When the lever is moved over a projecting member fixed at a pre-Determined position on either side of the gantry, the power supply to the motor is cut off. The contacts are automatically reset when the lever returns to `Zero’ position due to spring action. The contacts are rated for 60 Amps at 415 Volts A. C. 50 cycles supply system.The side covers are of cast iron. The top and bottom covers are of sheet steel. The lever is of Mild Steel fitted with M. S. Roller. Hoist Series Limit Switch: “STERLING” Hoist Series as differential Limit Switches is used to prevent over hoisting. The Limit Switch will normally remain `ON’ due to the weight connected to the lever. When the snatch block reaches the highest position the weight pulling the lever down is moved up on the snatch block, hence the lever is released and the two snap action contacts cut off 2 phases of the motor thereby stopping the hoisting motion. The contacts are automatically reset when the snatch block is lowered. The contacts are rated for 60 Amps at 415 Volts A. C. 50 cycles supply system. Heavy Duty Hoist Limit Switch with contacts rated for 150 Amps at 415 Volts A. C. 50 cycles with arc chutes and blow out coils can also be supplied. Rotary Shunt Limit Switch: “STERLING” Rotary Shunt & geared Limit Switches is also used to prevent over hoisting. One set of contacts cut off supply to the coil circuit of the HOIST contactor, after about 6 revolutions of the spindle the other set of contacts cut off supply to the coil circuit of DOWN contactor. The contacts are automatically reset when the spindle rotates in the reverse direction. The position of the switch operation is adjustable within 6 revolutions with one over turn in either direction. The spindle can be chain or gear driven with required reduction ratio to suit individual requirement. The Limit Switch is housed in totally enclosed fabricated steel housing with contacts rated for 10 Amps at 415 Volts A. C. 50 cycles supply system. Two Way Shunt Limit Switch “STERLING” Two Way Shunt Limit Switch is also used to prevent over travel or over traverse. The Limit Switch is fitted with 2 numbers of double break silver tipped contacts which remain normally closed and supply power to the contactor coil in the control panel. When the lever is moved over a projecting member fixed at a pre-determined position on either side of the gantry, the power supply to the contactor coil is cut off. The contacts are automatically reset when the lever returns to `Zero’ position due to spring action. The contacts rated for 10 Amps at 415 Volts A. C. 50 cycles supply system.

Electro Hydraulic Thrustors consists of a cylinder filled with oil containing the centrifugal pump located at the bottom and electric motor assembled on the top cover. The Rotor Shaft of the Motor is extended vertically downwards in the cylinder and carries an impeller at its lower end. The top bearing of the motors are grease lubricated and the bottom bearing is splash lubricated from oil in the tank. The Thrustor motors are totally enclosed `B� class insulated, suitable for AC 400440 Volts, 3 phase, 50 Hz supply. Electro Hydraulic Thrustor is robust and dependable, possessing the stamina needed for the toughest duty conditions imposed by unattended drives in any industry. Because of its extra-ordinary versatility it has wide applications in electrically driven Hoists, Cranes, Elevators, Ropeways, Flap Valves, Guillotine Machines, Conveyors, Steel Mills, etc.

Application: STERLING Electro Hydraulic Thrustor is robust and dependable, possessing the stamina needed for the toughest duty conditions imposed by unattended drives in any industry. Because of its extra-ordinary versatility it has wide applications in electrically driven Hoists, Cranes, Elevators, Ropeways, Flap Valves, Guillotine Machines, Conveyors, Steel Mills, etc. Construction: The STERLING Electro Hydraulic Thrustors consists of a cylinder filled with oil containing the centrifugal pump located at the bottom and electric motor assembled on the top cover. The Rotor Shaft of the Motor is extended vertically downwards in the cylinder and carries an impeller at its lower end. The top bearing of the motors are grease lubricated and the bottom bearing is splash lubricated from oil in the tank. The Thrustor motors are totally enclosed `B’ class insulated, suitable for AC 400/440 Volts, 3 phase, 50 Hz supply. When the motor drives the impeller, it pumps the oil from the upper to the lower side of the piston. In model 47-2040 Thrustor, the whole motor and end shield assembly move up during power stroke. In  all  other  models inside the cylinder, above the impeller is a piston with thrust rods connected by a cross bar which delivers the useful thrust. When the power to the motor is switched off, the impeller stops, oil flows in the reverse direction through the stationery impeller, and the load forces the piston down. The thrustor is not susceptible to mechanical overloads because if external load exceeds the lifting force of the thrustor its piston will remain stationery while the pump will continue to operate building up normal working pressure of the fluid under the piston. This gives rise neither to excessive current in the motor nor to excessive stresses in the thrustor elements. Features: We STERLING controllers like other Manufacturers for Electro Hydraulic Thrustors deliver gentle thrust without any jerks, consuming very negligible power. It is rated for 100% continuous duty and can withstand many switching operations without over heating the motor. They can be fitted up to 10 degree from the vertical in either direction due to swivel mounting arrangement.

Application:  STERLING Drum Controllers are used in all types of electric operated cranes like many other Manufacturers to control all motions. They are also used in hoists and winches as well as for speed control of slip ring or squirrel cage motors in various machines. Construction:  STERLING Drum Controller is housed in a sheet steel enclosure with top and bottom plates of cast iron. The front cover is easily removable giving ample space for maintenance. The brake drum and couplings is the large diameter giving generous wearing surface and an increased arcing distance between the segments and tips. The drum contacts are of heavy gauge hard drawn copper, screwed to the cast iron drum with counter sunk head screws. Exact location of the contacts at each step is ensured by the provision of a ratchet wheel engaging on adjustable spring loaded pawl-lever fitted with roller. The square drum shaft is provided with square Bakelite tube to insulate the drum castings. The main contact fingers are of hinged pattern rigidly clamped to the Bakelite insulated steel square bar. Each finger consists of heavy section brass bar fitted with renewable hard drawn half round copper tip. The fingers engage with the rotary drum under helical spring pressure. The laminated copper shunts carry the current from the fingers to the terminal bases. The terminal bases are also of extruded brass. The brass parts and copper contacts are cadmium plated. Substantial arc shields on all main contacts are provided. The whole arc shield assembly can be removed for inspection of contacts and any damaged section of arc shield can be very easily replaced. All Drum Controllers are suitable for 400/440 Volts, 3 Phase, 50 cycles AC supply. Features: STERLING Drum Controllers Manufacturer are provided with ‘ZERO’ interlocking contacts. Options available are shunt limit switch contacts, dead main’s handle, double rotor and dust proof cover. The Drum Controllers are of rebuts construction for long life but are easy for operation with low maintenance.