Machine Parts

Definition of Friction: A force acting in the opposite direction to the motion of the body is called force of friction or simply called friction. Types of friction: There are two types of friction and they are 1. Static Friction 2. Dynamic Friction Static Friction: The friction experienced by a body, when at rest is called static friction. Dynamic Friction: The friction experienced by a body, when in motion is called dynamic friction. It is also known as kinetic friction. There are two types of dynamic friction a. Sliding Friction b. Rolling Friction Sliding Friction: The friction experienced by a body, when it slides another body  is called sliding friction. Rolling Friction: The friction experienced by a body when balls or rollers are interposed between the two surfaces is called Rolling Friction.

Moment of Inertia: Moment of Inertia defined as the moment of the moment that is second moment of mass or area of a body. It is mathematically expresses by I M= Total mass of a body K= distance I=MK 2      

1 - Case The tube that homes the elements of the torch , as well as the batteries and lamp (light bulb). 2 - Contacts a really skinny spring or strip of metal (usually copper or brass) that's set throughout the torch , creating the electrical affiliation between the assorted elements – the batteries, the lamp, and also the switch. These elements conduct electricity and "hook everything up," finishing the circuit. 3 - Switch The flow of the electricity is activated after you push the switch into the ON position, providing you with lightweight . The flow of electricity is broken once the switch is pushed into the OFF position, therefore turning off the sunshine . 4 - Reflector A plastic half , coated with a shiny metallic element layer that rests round the lamp (light bulb) and redirects the sunshine rays from the lamp to permit a gradual ray , that is that the lightweight you see emitting from the torch . 5 - Lamp the

ACME transformers should be specified to: 1.Distribute power at high voltage.   2.Eliminate double wiring. 3.Operate 120 volt equipment from power circuits. 4.Insulate circuits/establish separately derived circuits. 5.Provide 3-wire secondary circuits.   6.Buck and Boost 7.Provide electrostatic shielding transient noise protection.

Since most single phase transformers have a secondary voltage of 120/240, they will be operated as a three wire system. Care must be taken in properly distributing the load as the transformer secondary consists of 2 separate 120 volt windings. Each 120 volt winding is rated at one-half the name plate KVA rating. For example: A 10 KVA transformer, 120/240 volt secondary is to service an 8 KVA load at 240 volts and two 1 KVA loads at 120 volts each. If the incorrect method is used, winding A will be loaded at 6 KVA, and winding B will be loaded at 4 KVA. These do total 10 KVA but since each winding is only rated at 5 KVA (1/2 of nameplate rating), we have an overloaded transformer and a certain failure. 

Each phase of a three phase transformer must be considered as a single phase transformer when determining loading. For example: A 45 KVA three phase transformer with a 208Y/120 volt secondary is to service 4 loads at 120 volts single phase each. These loads are 10 KVA, 5 KVA, 8 KVA, and 4 KVA. That maximum loading on any phase does not exceed 10 KVA. Each phase has a 15 KVA capacity.  45 KVA = 15 KVA per phase         _____        3 phase  If incorrect method is used, phase B will have an 18 KVA load which is 3 KVA above its normal capacity of 15 KVA and failure will result even though we only have a total load of 27 KVA on a 45 KVA transformer. 

Yes. There are occasions where 480 volts single phase can be stepped down to 240 volts single phase by autoconnecting a standard. If connected in this manner, the nameplate KVA is doubled.

Industrial control equipment demands 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 sealed or holding currents but still maintain normal voltage at this momentary overloaded condition. Distribution transformers are designed for good regulation up to 100 percent loading, but their output voltage will drop rapidly on momentary overloads of this type making them unsuitable for high inrush applications. Industrial control transformers are designed especially for maintaining a high degree of regulation even at eight times normal load. This results in a larger and generally more expensive transformer. For a complete listing of ACME industrial control transformers, refer to Section V in the ACME catalog. 

The minimum transformer KVA rating required to operate a motor is calculated as follows:  Minimum Transformer KVA  Running Load Amperes x 1.73 x Motor Operating Voltage _____________________________________________________                                          1000  NOTE: If motor is to be started more than once per hour add 20% additional KVA.  Care should be exercised in sizing a transformer for an induction type squirrel cage motor as when it is started, the lock rotor amperage is approximately 5 to 7 times the running load amperage. This severe starting overload will result in a drop of the transformer output voltage. When the voltage is low the torque and the horsepower of the motor will drop proportionately to the square of the voltage. For example: If the voltage were to drop to 70% of nominal, then motor horse power and torque would drop to 70% squared or 49% of the motor nameplate rating. The underlying problem is low voltage at the moto

DITs, as the name implies, are designed to be used with motor drives (AC and DC) and to provide isolation from the service line. They are specifically designed to withstand the "short circuit-like" duty imposed by the filing of the thyristors. Harmonics generated by drives create added loads on the transformer. Therefore, it is important that a transformer of equal or greater KVA to that recommended by the drive manufacturer be installed for a particular motor application.