The three most commonly used electrical test instruments are: the clamp-on amp meter, the AC voltmeter, and the Ohmmeter. These three meters are commonly known today as digital multimeters (DMM). It is vitally important that electrical personnel know how to correctly use a DMM. These meters are used to not only understand how an electrical …
This article covers the following items about electrical timers: The five sections of timers Nine timer operating principles Five common modes of timer operations Timer charts Sections of Electrical Timer Figure 1 provides a block diagram that shows the five functional sections of a timer. Timers can be divided into the following sections: Power or …
Variable Frequency Drive Working A variable frequency drive (VFDs) uses solid state electronic circuits to provide a signal to a motor to control its acceleration, deceleration, direction of rotation, torque, and horsepower. Drives do this by converting a fixed frequency (either 50 or 60 Hz) AC power source, to a variable frequency power supply to …
Generally, it can be stated that a circuit breaker is intended to protect the electrical conductors in the circuit from overheating. It can also be stated that the equipment grounding conductor (EGC) is required by the NEC to be connected so that a low impedance fault current path is provided for the main purpose of …
Molded Case Circuit Breakers or MCCB circuit breakers are black plastic–cased automatic switches. They are designed to primarily protect insulating materials from overheating. Molded case circuit breakers (MCCB) are by far the most commonly used breakers in residential, commercial, and industrial facilities. When an MCCB has opened (or “tripped”) to protect the circuit, it can …
The term “power factor” (PF) is an expression of the relationship between the peak voltage and the peak current. Stated differently, the power factor is an expression of how far out of phase the voltage and current are to each other. What is power factor? Figure 1 shows both voltage and current peaks occurring at …
A control panel is used to house instruments used for measurement, monitoring, protection, detection, control, and management of processes. For operational convenience, these panels are located in a control room as well as a field known as a local control panel. Types of Electrical Control Panels Industrial Panels VCB Panel (HT Section): A Vacuum Circuit …
1. A transformer will work on (i) a.c. only (ii) d.c. only (iii) a.c. as well as d.c (iv) none of the above 2. The primary and secondary of a transformer are ……… coupled. (i) electrically (ii) magnetically (iii) electrically and magnetically (iv) none of the above 3. A transformer is an efficient device because …
1. The yoke of a d.c. machine is made of (i) silicon steel (ii) soft iron (iii) aluminium (iv) cast steel 2. The armature of a d.c. machine is made of (i) silicon steel (ii) wrought iron (iii) cast steel (iv) soft iron 3. The coupling field between electrical and mechanical systems of a d.c. …
1. An ammeter is …………… instrument. (i) an indicating (ii) an integrating (iii) a recording (iv) none of the above 2. The controlling torque of an indicating instrument ………. as the deflection of the moving system increases. (i) remains unchanged (ii) decreases (iii) increases (iv) none of the above 3. When the pointer of an …
