T&L Publications

How can I bench test a capacitor without any specialty capacitor test equipment? The tools available are a Fluke Meter(with capacitor test function) and some jumper leads. The type of capacitors are used in central air conditiong units and are about the size of a small soda can. The one I tested tod...

I have a tranformer with 2 primary connections at 480vac and 2 secondary connections at 24vac . The transformer is labled "250va" . It is used to power 2 24vdc solenoids through 2 Full wave bridge rectifiers. How much amperage is available for the 2 solenoids? The solenoids are about as bi...

I have a transformer in my garage. It was used with 480v input and put out 135v. The rating on the side says 200va. If I hook it up to 120v household power (primary side) what voltage should I expect and what amount of amperage will be available on the secondary output?

On a hydraulic elevator the elevator is raised and lowered by opening solenoid activated valves. The solenoid has an electromagnetic coil that just sits over (around) a cylindrical spring loaded mechanical valve. When energized it just raises the valve off it's seat. The metal valve sits in the cent...

An ac motor has a running amperage of 10 amps and the measured voltage is 120volts ac. If the voltage drops to 110volts, what amperage would you expect to measure on a meter. HIGHER than 10 amps or LOWER than 10amps? 9.2 amps? , 10.8 amps? or??

Gentlemen, the test questions I posted are NOT!! trick questions, and I am sorry if you thought I was trying to fool you in some way. I very much value your input on ANY of my postings. I WOULD NOT waste your time. These 2 questions came off a real test from my company. They deal with a job that con...

The general function of an auxillary relay is to assist (a) undervoltage relay (b) protective relay (c) phase relay (d) reverse current relay

A voltage tester is a good tool for determining the _________ available from a power source? (a) nominal voltage (b) approximate voltage (c) exact voltage (d) all of the above

I seem to remember something about the subject of "positive logic" and "negative logic" that deals with 1's and 0's . there may be questions on an upcoming test. Can anyone give a brief review on what this is? EX... in positive logic 1 is high and 0 is low, but in negative logic ...

I think I know the difference between neutral and ground in my house, but what is the difference in industrial applications when dealing with high voltage and three phase? How come some systems are grounded and some are not? The "ground" on an automobile is basically the return side of the...

What is a zener diode? What is it used for and what's the difference between a regular diode and a Zener?

I came across weird volt readings in work today. Maybe someone has an explanation. Working with THREE PHASE 480V heaters. At the disconnect the voltage (when the disconnect was open) was 480V between any two legs. And 277V from any leg (3) to ground. But with the disconnect closed, voltage between o...

Don't all latching relays (24v dc ice cube type) have 2 coils, one for latching and one for unlatching? Is there a latching relay that has a coil for latching and a pushbutton (that sticks through the side) for unlatching? I thought the pushbutton on the single coil relays was for activating the rel...

I have an escalator safety circuit that consists of switches, many relay contacts (of different relays), and some internal PLC contacts that are all in series. If any link in this chain is broken it affects other links and the machine will shut down within one second. My problem is finding what part...

Where I work they have high voltage (277vac) "metal Halide" lights. These lights normally take time to come on completely (to full brightness), but occasionally they go off and the electrician has to replace the "ballast". These ballasts look alot like transformers, some have thr...