Follow us

Signage Civil & MEP

Al Inshrah is also well known in the industry, as the leading manufacturer and supplier of all kinds of Signs, Underground Warning tapes, Engraving, Acrylic Fabrication etc.

Read More

Bus bar trading

Al Inshrah also plays a major role in busbar trading, as we are one of the leading stockists of Tinned/Bare Copper Busbar in the Middle East.

Read More

Signage Material Trading

We deliver really a wide range of sign materials both for indoor uses and outdoor purposes. PVC/Traffolyte/Acrylic Sheets/Engraving Cutter, Colour vinyl rolls, Indoor/Outdoor...

Read More

Relay

Over Voltage Relays
Over Voltage Relay
Over Voltage Relays

Relay which operates at precise voltage levels to actuate the relay when either a low voltage or high voltage is experienced.

The contacts on this relay are inserted in the shutdown scheme of the device which is to be operated when these conditions exist. The contacts can operate a shunt-trip on a circuit breaker to open the circuit breaker. They can also activate an alarm. These relays are used in many control schemes.

Overload Relays
Overload Relays
Overload Relays

A relay that opens a circuit when the load in the circuit exceeds a preset value, in order to provide overload protection; usually responds to excessive current, but may respond to excessive values of power, temperature, or other quantities. Also known as overload release.

A relay that is attached to a contactor in order to create a motor starter. Overload relays protect the motor from overload by disconnecting the power to the motor and stopping its operation.

Electric motors need overcurrent protection to prevent damage from over-loading the motor, or to protect against short circuits in connecting cables or internal faults in the motor windings.[6] The overload sensing devices are a form of heat operated relay where a coil heats a bimetallic strip, or where a solder pot melts, releasing a spring to operate auxiliary contacts. These auxiliary contacts are in series with the coil. If the overload senses excess current in the load, the coil is de-energized.

This thermal protection operates relatively slowly allowing the motor to draw higher starting currents before the protection relay will trip. Where the overload relay is exposed to the same environment as the motor, a useful though crude compensation for motor ambient temperature is provided.

The other common overload protection system uses an electromagnet coil in series with the motor circuit that directly operates contacts. This is similar to a control relay but requires a rather high fault current to operate the contacts. To prevent short over current spikes from causing nuisance triggering the armature movement is damped with a dashpot. The thermal and magnetic overload detections are typically used together in a motor protection relay.

Electronic overload protection relays measure motor current and can estimate motor winding temperature using a "thermal model" of the motor armature system that can be set to provide more accurate motor protection. Some motor protection relays include temperature detector inputs for direct measurement from a thermocouple or resistance thermometer sensor embedded in the winding.

Phase Sequence Relays
Phase Sequence Relays
Phase Sequence Relays

Relay which functions according to the order in which the phase voltages successively reach their maximum positive values. Also known as phase-rotation relay.

Plug-in Relays
Plug-in Relays
Plug-in Relays

Relays that are held in the socket by flat plug in terminals

Reverse Power Relay
Reverse Power Relay
Reverse Power Relay

Reverse Power Relay - Function and Operation

A reverse power relay is a directional power relay that is used to monitor the power from a generator running in parallel with another generator or the utility. The function of the reverse power relay is to prevent a reverse power condition in which power flows from the bus bar into the generator. This condition can occur when there is a failure in the prime mover such as an engine or a turbine which drives the generator.

Causes of Reverse Power

The failure can be caused to a starvation of fuel in the prime mover, a problem with the speed controller or an other breakdown. When the prime mover of a generator running in a synchronized condition fails. There is a condition known as motoring, where the generator draws power from the bus bar, runs as a motor and drives the prime mover. This happens as in a synchronized condition all the generators will have the same frequency. Any drop in frequency in one generator will cause the other power sources to pump power into the generator. The flow of power in the reverse direction is known as the reverse power relay.

Another cause of reverse power can occur during synchronization. If the frequency of the machine to be synchronized is slightly lesser than the bus bar frequency and the breaker is closed, power will flow from the bus bar to the machine. Hence, during synchronization(forward), frequency of the incoming machine is kept slight higher than that of the bus bar i.e. the synchroscope is made to rotate in the "Too fast" direction. This ensures that the machine takes on load as soon as the breaker is closed.

Setting the Reverse Power Relay

The reverse power relay is usually set to 20% to 50% of the motoring power required by prime mover. By motoring power we mean the power required by the generator to drive the prime mover at the rated rpm. This is usually obtained from the manufacturer of the prime mover

Timer Relay
Timer Relay
Timer Relay

Time delay relays (TDRs) can provide simple, reliable, and economical control. Adjusting the delay time is often as simple as turning a knob. Providing time-delayed switching to start a motor, control a load, or affect a process, TDRs are typically used in industrial applications and OEM equipment. Additionally, they play an important role for targeted logic needs, such as in a small panel or in sub-panels. They have a variety of features and operating characteristics, such as compactness, economy, simplicity, and ease-of-use.

In a standard control relay, contacts close immediately when voltage is applied to the coil, and open immediately when voltage is removed. In a variety of applications, it’s desirable to have the operation of the contacts delayed following application or removal of voltage. A TDR solves the problem handily. However, some TDRs postpone closing of the contacts after voltage is applied while others close the contacts — and then reopen them after a delay.

TDRs are available as plug-in devices, much like plug-in control relays. However, they are also available in a range of other forms, including base-mounted devices and direct IEC DIN-mounted controls. For instance, a TDR can be fixed on a motor starter. In this application, energizing the motor starter causes the timing function to begin; contacts within the device operate when timing is complete. Electronic, starter-mounted TDRs are also available. Some TDRs have solid-state outputs instead of relay outputs.

Traditionally, TDRs were available only as single-function, single-time-range devices. These devices are still available and are typically used in applications where the timing needs to be locked in. Today, many TDRs are also available with multiple timing ranges and functions. Costing little more than single-function devices, these TDRs also have wide control voltage ranges. In addition, newer multifunction IEC-style timers allow for reduced inventories.

The micro switch works by using very physical force through the use of a tipping-point mechanism. The switching happens reliably at specific and repeatable positions of the actuator, which is not necessarily true of other mechanisms. Internally, it has a flat metal spring that must be bent to activate the switch. Inside is a small curved spring.

Under Voltage Relay
Under Voltage Relay
Under Voltage Relay

A relay designed to operate when its coil voltage falls below a predetermined value.

Voltage relays are electrical devices in which the primary function is the switching of current from one circuit to another. The use of a voltage relay makes it possible to control a large amount of current with a small amount of current. The relay is activated remotely using an electrical signal. In some applications, the remote signal might be pneumatic.

Voltage relays can be found in a broad range of applications. One of the most common, and earliest, uses is in the switching exchanges of the telephone and telegraph industry. They also are widely used in automated testing equipment as well as being found in most major appliances and electronics, including computers.

In a typical relay, there is a lever that makes a connection with a contact. When the lever and contact are touching each other, the circuit is said to be closed. When the two components are not touching, the circuit is considered open. When the relay is actuated, the lever is moved from its present position to the other position, from open to close or vice-versa. This action serves to relay power from one circuit to another circuit.

One of the basic uses of voltage relays is in simple on/off control. An example of this would be in a refrigeration system that runs a compressor. When the compressor comes on, a surge of electrical current is required to initially power it up. A voltage relay is used to redirect, or relay, current to the compressor’s circuit at the appropriate time.

Voltage relays are also used in logic applications. This function is particularly prevalent in equipment used for testing. The voltage relay provides the capability of moving current from one point to another in a defined logical sequence.

The two broadly defined categories of voltage relays are electromechanical and solid state. There are a variety of different styles and types under each classification. Electromechanical voltage relays contain moving, mechanical parts. The action of the relay is actuated by current flowing through a wire coil, which creates a magnetic field to operate the relay. The magnetic force is used to move the contact lever, causing either an open circuit to close or a closed circuit to open.

Solid-state voltage relays use light from light emitting diodes to achieve actuation of the relay. The lack of moving parts makes them more durable than the electromechanical types. Additionally, solid-state relays typically have faster reaction times, making them more efficient.

Another attribute by which voltage relays are characterized is the amount of load, or current, they are capable of handling. In most cases, relays are classified as either low-voltage relays or high-voltage relays. In general, high-voltage relays operate at voltages of more than 5,000 volts. There are, however, applications in which a high-voltage relay is used at a lower rating.