Solid-State Relays and Starters 375

ambient temperature

For solid state devices, the temperature of the air inside the equipment enclosure as well as the air outside the enclosure.

analog switching relay

A type of solid state relay in which voltage is ramped up in stages after it is applied to the line. Analog switching relays can output any level of voltage that the relay is rated to handle.

anode

The positively charged terminal of an electronic switch. Anodes are used in solid state components like SCRs to control current.

arcing

The act of producing an electric arc. Electric arcs can cause a great deal of damage to electronic equipment, and they are dangerous to people as well.

brake stop

A solid state motor stopping mode that allows the amount of braking to be programmed according to the application. This also affects braking time, allowing for a faster stop.

bridging

The unintended joining of two or more adjacent pads on a PCB, creating a faulty electronic connection. Condensed moisture can create bridging between conductors on a PCB.

cathode

The negatively charged terminal of an electronic switch. Cathodes are used in solid state components like SCRs to control current.

circuit analysis

A troubleshooting method used when a relay fails to turn the load on or off, or operates erratically. Circuit analysis is used when the relay is not suspected as the primary cause of malfunction.

closed loop application

An application in which the amount of output is directly proportional to the amount of input signal.

conduit

A tubular enclosure for holding wires or cables. Conduits should be used to minimize electrical noise in wires by keeping them separate.

control circuit

The part of a solid state relay that determines when the output component is energized or de-energized. The control circuit performs the same functions in solid state relays as the coupling between the input and output circuits does for electromechanical relays.

control conductor

A wire that carries 240 VAC or 460 VAC. Also known as a power wire.

control voltage

The minimum voltage required to gate or activate the control circuit of a solid state relay. Also known as pickup voltage.

current limit start

A solid state motor starting method that limits the starting current to a programmed value ranging from 50 percent to 600 percent of the motor's full load current. This helps to reduce starting torque, which in turn reduces stress on the power distribution system.

diode

A solid state device that allows electricity to flow in only one direction.

dip switches

Dual In-line Package switch. DIP switches use binary settings, on-off / yes-no, to configure various options on a device.

electrical noise

An AC power line disturbance caused by sudden changes in the load. Electrical noise is problematic to solid state devices because they cannot differentiate between an intended electrical pulse and an unintended electrical spike.

electrostatic discharge

Current produced by two objects having a static charge when they are brought close enough together to produce an arc or discharge, which appears as static electricity. Electrostatic discharge can destroy small electronic devices.

gate

The control terminal of an electronic switch. Gates are used in solid state components like SCRs to control current.

heat sink

A conductive metal sheet with large fins that dissipate heat. Heat sinks help protect solid state devices from damage caused by thermal stress.

input circuit

The part of a solid state relay to which a control component is connected. The input circuit performs the same function in solid state relays as coils do for electromechanical relays.

instant-on switching relay

A type of solid state relay in which the load is turned on immediately when control voltage is applied to the line. Instant-on relays control inductive loads.

isolation transformer

A transformer used to reduce or eliminate electrical noise by modifying the amount of voltage or current on the line.

LED

Light-emitting diode. A semiconductor device that emits a narrow-spectrum of light in a forward direction.

light-emitting diode

A semiconductor device that emits a narrow-spectrum of light in a forward direction. Also known as an LED.

load switching circuit

The load switched by the solid state relay. The output circuit performs the same function in solid state relays as mechanical contacts do for an electromechanical relay.

maximum load current rating

A determination made by the manufacturer as to the highest amount of load current a device can reliably carry.

off-state leakage current

The amount of current required to keep a device active when it is not operating. Also known as load current and residual current.

optical isolation

A method of controlling solid state relays by using two circuits that are insulated from each other by an optocoupler that converts electric current to light and then back into electric current.

optical isolator

A solid state component that uses a light-emitting diode to transmit light through an optically transparent barrier between two isolated circuits. This barrier insulates circuits by allowing light to pass through, but not current.

optocoupler

A solid state component that uses a light-emitting diode to transmit light through an optically transparent barrier between two isolated circuits. This barrier insulates circuits by allowing light to pass through, but not current.

output circuit

The load switched by the solid state relay. The output circuit performs the same function in solid state relays as mechanical contacts do for an electromechanical relay.

parameter

A set of rules, limits, or physical properties that determine the characteristics or behavior of something. In solid state motor starters, parameters may include the trip class, or starting and stopping mode.

peak switching relay

A type of solid state relay in which control voltage is applied to the line and the load is turned on when the AC sine wave reaches its peak. Peak switching is used when voltage and current are out of phase with each other by 90 degrees.

photo-sensitive detector

The element of an optical isolator that detects and responds to the light emitted by the LED. Photo-sensitive detectors are used in optical isolators.

pickup voltage

The minimum voltage required to gate or activate the control circuit of a solid state relay. Also known as control voltage.

pump control

A solid state motor stopping mode used specifically for centrifugal pumps. This stopping method provides smooth acceleration and deceleration by reducing surges that occur during starting and stopping.

SCR

Silicon controlled rectifier. A diode with an extra junction that forms a gate preventing current flow in either direction until it receives a voltage signal. Also known as a thyristor.

signal wire

A low voltage (usually 10 volts DC or 1-20 mA or less) non-control device used on transducers. Signal wires are for devices that use shielded wires.

silicon controlled rectifier

A diode with an extra junction that forms a gate preventing current flow in either direction until it receives a voltage signal. Also known as an SCR or a thyristor.

sine wave

The most common type of AC waveform. A sine wave consists of 360 electrical degrees and is produced by rotating machines.

soft start

A solid state motor starting method that reduces stress on a motor by allowing it to accelerate gradually for a programmed period of time.

soft start with start boost

A solid state motor starting method used for loads that are hard to start in regular soft start mode. Soft start with start boost sends a pulse to the motor during startup that provides additional starting torque.

soft stop

A solid state motor stopping mode in which deceleration is controlled by the starter instead of the load. Soft stop is used on friction loads that tend to stop suddenly when voltage is removed from the motor.

solid state device

A device that is purely electronic with no moving parts. Solid state devices are generally faster, more reliable, and less expensive than their electromechanical counterparts.

solid state motor starter

A control device that protects a motor from overload by using solid state components instead of contacts to start and stop current flow. Solid state motor starters work more safely and efficiently than mechanical motor starters because they reduce large electrical spikes.

solid state relay

An electronic switch that contains no moving parts. Solid state relays are rapidly replacing electromechanical relays.

surge suppressor

A device that protects equipment from damaging electrical surges by regulating the voltage on the line.

thermal grease

A paste often applied between metal surfaces to increase the conduction of heat between them. Thermal grease should always be applied between a solid state device and a heat sink.

thyristor

A diode with an extra junction that forms a gate preventing current flow in either direction until it receives a voltage signal. Also known as a silicon controlled rectifier or SCR.

triac

An electronic switch that allows small control voltages and currents to switch very large voltages. Triacs can conduct current in either direction.

trip class

A numeric rating that correlates to the amount of time it takes to break the circuit when an overload condition occurs. A class 10 relay breaks the circuit within 10 seconds of overload, a class 20 relay breaks the circuit within 20 seconds of overload, etc.

twisted pair

Two insulated copper wires that are twisted around each other to reduce electromagnetic induction from one wire to the other.

varistor

A device that protects the relay against overvoltage by diverting high voltages away from sensitive components. A varistor's rating should be a minimum of 10% higher than the line voltage of the output circuit.

voltage drop

The amount of energy used by a device with resistance in the circuit. In a series circuit, voltage drop increases as resistance increases, and decreases as resistance decreases.

voltage spike

A sudden, short surge in voltage. Voltage spikes can be caused by lightning, power outages, short circuits, or power transitions in large equipment on the same power line.

wiring tray

A device for organizing and managing multiple electrical wires. Wiring trays should be used to minimize electrical noise in wires by keeping them separate.

zero switching relay

A type of solid state relay in which the load is turned on when the AC sine wave crosses zero. Zero switching relays are used for resistive, inductive, or capacitive loads.