Acronyms

Question 1

PWM

Answer 1

Pulse Width Modulation - a square wave output chopped to approximate an AC sine wave.

Question 2

SCR

Answer 2

Silicon Controlled Rectifier - an electronic power device that blocks the passage of current when the voltage across is negative. When the voltage across the SCR is positive, current can pass through it if a small positive signal is applied to its control input, which is called a gate. The SCR can convert AC to DC. Using a control activated when the SCR gate is triggered, the DC amount can also be controlled.

Question 3

SLD

Answer 3

Signal Level Detector - a device that compares on signal to another. The SLD outputs the result as zero if A < B and a one if A > B. The SLD device can be created in either hardware or software. Zero speed is one type of signal generated by an SLD. Speed is compared to a constant, zero (or around zero). The output is zero when the speed is < zero and a one when speed is > zero. SLD’s usually have adjustments for taking absolute values of signals, adding time delays, inverting values, etc.

Question 4

TOC

Answer 4

Time Overcurrent - can be used interchangeable with TOL. Some manufacturers use TOL to pertain to motor protection and TOC for drive protection. In this case, it protects the drive bridge from thermal overloads. If the bridge rating exceeds the motor rating, a drive may use either one.

Question 5

TOL

Answer 5

Thermal Overload - extended over a long period of time can cause motor overheating, which shortens the motors life and could cause a fire. Electrical codes require motors to have protection against loads that exceed 100 percent of their rating after a specific time has elapsed.