D Type Relays, Plug Relay, Electromechanical Relays, SSR Relays, Terminal Blocks, Industrial Relays, Mumbai, India
 

D Type Relays, Plug Relay, Electromechanical Relays, SSR Relays, Terminal Blocks, Industrial Relays, Mumbai, India

 
Why to Use Relay & Differentiation
 
Why use a relay vs a circuit breaker or switch?
By definition:
RELAY : An electromagnetic device for remote or automatic control that is actuated by variations in conditions of an electric circuit and which, in turn, operates other devices (such as switches) in the same or a different circuit.
CIRCUIT BREAKER : A switch that automatically interrupts an electric circuit under an infrequent abnormal condition; e.g., a fault condition such as an overload or rupture of either high voltage or high current or both.
SWITCH : A device for making, breaking, or changing the connections in an electrical circuit. Usually mechanical and operated by hand.
 
What does normally open, normally closed mean?
The word “normally” refers to de-energized condition of the relay (no power on coil).
The second words “open” and “closed” refer to the position of the contacts at the de-energized condition.
 
What is the difference between 50, 60, and 400 HZ?
Most AC (alternating current) relays operate on standard frequencies and voltages.

50 HZ FREQUENCY :
This is a standard alternating current frequency used mostly in Europe, Africa, Australia and Asia.
Voltages commonly used with thisfrequency are: 11 5VAC 10, 115/220 30, 220VAC 10, 220/440 30.

60 HZ FREQUENCY :
This is a standard frequency used primarily in the USA and Canada, but it is also used in many other countries.
The typical voltages used in households and industries are 11 5VAC 10, 115/200 30, 220/400 VAC.
In some instances heavy industry will use 440/66OVAC 30.

400HZ FREQUENCY :
This is a standard frequency used in most commercial/military aircraft. It is also used on Navy aircraft carriers, but primarily to service aircraft.
Most aircraft utilize the 115/208 VAC 400 HZ WYE system, except some newer aircraft,
which use 230/400 VAC 400 HZ because of its lighter weight generator system.

The 400 HZ frequency is used in aircraft systems primarily because the generators are much lighter in weight. 50/60 HZ frequencies are used because that was the chosen frequency by the federal government years ago, and no one has upgraded the frequency because of the associated cost.

 
What is the difference between resistive, inductive, motor, and lamp loads?

We must express the load as a contact rating, which is the electrical load-handling capability of relay contacts under specified conditions
and for a prescribed number of operations or life cycles.

RESISTIVE LOAD : A resistive load usually consists of some sort of resistance in the circuit; e.g., heaters, resistors, etc.

INDUCTIVE LOAD : An inductive load consists of a load created by a wire wound coil, such as in a relay or solenoid, a transformer, or any load
which uses a winding over a magnetic iron core. Breaking an inductive load is usually more severe than breaking a resistive load and will generally produce heavy arcing.

MOTOR LOAD : A motor load can be referred to as a rotating inductive load, generally with a high inrush of six times the normal load.
The breaking of the load is much the same as a resistive load.

LAMP LOAD : There are many types of lamp loads such as tungsten filament, fluorescent, mercury-vapor, and other exotic gas lamps.
The loads we normally concern ourselves with are tungsten filament. Tungsten filament lamps, when first turned on, will draw an inrush current of 10-15 times of the steady-state current. The inrush is similar to a motor load inrush and is caused by the cold filament in the lamp.
After the lamp filament has heated up, the current will drop to its normal level. Most tungsten filament lamp load ratings are 20% of a resistive load.

 
Why do we have 3-phase ratings available?

3-phase power is used over 1-phase power primarily for weight reduction/saving and efficiency in smoother running accessories.
The 3-phase circuits will deliver both 208 VAC as well as 115 VAC with more torqueing power.

Delta Systems are used almost exclusively aboard military naval vessels. This is done because there is no ground in the system.
This method is used to protect personnel on board. Should any phase come in contact with ground, the person shorting himself to any one of the three phases can never short to ground and, therefore, will never be electrocuted

 
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