Relays & Logic
These switching devices have many advantages over electromechanical relays, including faster switching and superior service life because they have no moving parts.
What are Solid-State Relays (SSRs)?
Solid-state, reduced-voltage starters are commonly referred to by this two-word term because of the smooth acceleration they provide.
What are soft-start controllers?
An AFD controls the speed of an AC motor by converting input power into these two adjustable variables.
What are frequency and voltage?
This braking method is controlled by a solenoid and is unique because it does not require any operating power source to provide braking force.
What is friction braking?
These are usually the very first items checked when a motor is inoperative.
What are fuses and circuit breakers?
This type of time-delay relay provides the time delay after the relay is de-energized.
What is an off-delay relay?
This conventional starting method uses a transformer to allow for adjustment of starting torque and inrush current for high-torque loads.
What is autotransformer starting?
This is the specific frequency at which an AFD transitions from a constant volts-to-hertz ratio to a constant voltage/varying frequency range.
What is the base frequency?
In this method, a DC voltage is applied to the motor stator windings for a timed interval; the braking energy is lost as heat.
What is DC injection braking?
When checking a fuse with a DMM, this resistance reading indicates that the fuse is "good" or has continuity.
What is zero ohms?
In an SSR, the input control circuit provides coupling to the output circuit using these two specific electronic components.
What are a Light-Emitting Diode (LED) and a photo detector?
This solid-state starting control method provides an initial burst of current to help break a rotor free from a hard-to-start load.
What is a kick start?
These loads, found in machines like hoists and conveyors, require the same amount of torque regardless of the speed.
What are constant-torque loads?
This specific braking method is the only one that saves energy by returning it to the incoming power source.
What is regenerative braking?
To reduce the amount of coupled noise in solid-state devices, this type of wiring must be used.
What is shielded wire?
This rule of thumb describes the impact of heat on an SSR's lifespan for every degree increase above its maximum permitted environmental temperature.
What is cutting the life span in half?
This starting method involves connecting motor leads in one configuration for starting and another for running to control high-inertia loads.
What is Wye-Delta starting?
This category of semiconductor devices, which includes SCRs and triacs, turns on with a pulse and only turns off when current is interrupted elsewhere.
What are Thyristors?
During dynamic or regenerative braking, the power connections are reconfigured so that the motor acts as this device.
What is a generator?
The voltage imbalance between any two legs of a three-phase voltage source must not exceed this specific percentage.
What is 2%?
In this SSR switching mode, the amount of output voltage varies as a function of the input voltage.
What is Analog switching?
This older method of motor control involves applying power to only a portion of the motor’s coil windings for starting.
What is part-winding starting?
This term represents the speed difference between the synchronous speed and the base speed, which allows induction motors to develop torque.
What is Slip?
When using DC braking, the amount of braking torque can be controlled by adding this specific component to the circuit.
What is a current-limiting resistor?
This is the recommended method/tool for cleaning solid-state devices according to the preventive maintenance slides.
What is a dry cloth or soft brush