Basics

Harmonic waves are commonly generated by any equipment that utilizes capacitors, think VFD and a multitude of single phase equipment. You will probably have to install power factor correction to get the best from your generators and these capacitors also generate harmonics. Unlike faults, the harmonics generated are not likely to trip the equipment circuit breakers and thus affect the power supply system. It causes ripples in the voltage sinus wave, one effect this produces in practical terms ...

Reactive Power is when the Current flow, caused by AC Voltage applied across a device, results in the Current flow being either ahead or behind the applied AC Voltage.

Reactive devices will store some Energy as Voltage is applied, and they will return that Energy later in the sine-wave... Think of a Spring... You put power into a Spring, then when you reduce or remove the force, such as Voltage, the Spring will spring back returning the energy put into it... No Energy is absorbed, ...

The most correct term - according to IEEE and IEC - is ASD (Adjustable Speed Drive). This refers to the electronic equipment used to regulate the operating speed of the motor and driven equipment by controlling the frequency and voltage applied to the motor.

NOTE that other terms in common use include (but are not limited to): VSD (Variable Speed Drive), AFD (Adjustable Frequency Drive), and VFD (Variable Frequency Drive), they are referring to the same motor drives, just different ...

A VFD-driven general purpose motor can overheat if it is run too slowly. (Motors can get hot if they’re run slower than their rated speed.) Since most general purpose motors cool themselves with shaft-mounted fans, slow speeds mean less cooling. If the motor overheats, bearing and insulation life will be reduced. Therefore there are minimum speed requirements for all motors.

General purpose motors can be run with VFDs in many applications; however inverter-duty motors are de ...

I've spent a good deal of time in the field recently trouble shooting motor problems and observed the following. Often the bus voltages run high. When the voltage is high the magnetizing requirement of induction motors is also higher. Often the assumption is that if the voltage is higher the current will be lower without considering motor efficiency or power factor. Motors are designed to perform best at their rated nameplate voltage. First make sure that your bus voltages are where they shou ...

Basic knowledge of power inverter
Power inverter mainly adopts the PWM at present, controller switch to DC rapidly in a pulse-period to ensure that the DC integral value is equal to the sampling values of AC sine wave at the same time. After filtered, more than 96% sine wave output can be realized. Pulse inverter is self-excited inverter that output voltage is pulse modulation. This kind of power inverter reduces the voltage and electric current pulse number by increasin ...

When calculating voltage drop please make sure that you are referring to the correct parameters. Don't get confused between voltage drop and voltage difference. Consider a busbar at the source at Voltage Vs and the voltage at the load as Vl. The voltage drop across a line impedance is deltaV and is equal to a vector quantity of the product of current and line impedance. The source voltage is then equal to the load voltage plus the voltage drop across the line added vectorially. The voltage di ...

VFD derating is a manufacturer requirement when equipment ambient temperature is above 40 C degrees OR when equipment site is above 3000 feet in altitude. It is clear for manufacturers and engineers to avoid temperature derating by having the VFD's ambient temperature not to exceed 40 C degrees. On the other hand, VFD's manufacturers claim on altitude derating is due to thinner air at higher altitude that compromises the heat dissipation from the electronics. Although, it is a real claim, man ...

More specifically, a low voltage (LV) motor is normally <1000 V or <600 V, depending on who you ask. They are usually wound with round enamel-covered wire. This is called random-wound or mush-wound coils. Medium voltage (MV) motors, with voltages up to 13.8 kV or even higher, are wound with rectangular cross-section copper wire with enamel or mica tape insulation, depending on the voltage level. This is known as form-wound coils.

Because form-wound coils must be individually ...

You should not mix voltage sags (caused by transmission/distribution faults) and voltage fluctuations (starting large motors), voltage transients, switching disturbances or fault disturbances (resulting in sags) ect. are different events.

Every time you speak about voltage sags, we are starting a discussion on power quality and reliability and the definitions, events and for identifying voltage profiles (profiles, durations...) the causes and for providing safe and reliable power s ...

As per IEC 62271.1, the rated short circuit current has a time constant of 45ms (approximately X/R=14.1 at 50 Hz). If your application requires a higher time constants, you may purchase a breaker designed to operate on short circuit currents with a time constant of 120ms. Thus if you assume that the relay takes 10mS to detect the fault and actuate circuit breaker shunt trip, it will be interrupting more DC current if the time constant is 120mS, while the AC component remains same.

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Power Transmission lines are usually very long, EHV Transmission lines used for wheeling of power. They are strung on very high lattice Towers. The transmission lines are of ACSR or AAAC conductors of appropriate current carrying capacities. In case of wheeling of large currents at say 400kV level, bundle conductors are used. They don't need any kind of insulation or jackets etc. as the ambient air serves as Air insulation. Thus maintaining requisite flash over distance vis'a vis, EHV voltage ...

Since there are several electrical standards: by frequency 50/60Hz, by low voltage (residential / commercial) use: 120-220-240-277-380-480V. and we could unify between European/American/Asian use changing all to DC 12Volts, which is used by cars. DC Green technologies are now present in power sources (solar panels) and most loads could be served in DC (led illumination, TVs and all electronic appliances) using USB co ...

When there is a phase to ground fault on the system and maintenance crew are trying to determine the source of the fault, they are even more danger considering first of all they are working on an energized system and the potential to having a phase to phase fault before resolving the first, can be potentially dangerous to life and the electrical system as a whole, also considering the heavy wear and tear of the insulation on the system and the shutdown time and cost if a fatally occurs. Why a ...

What are some factors in choosing a Four Wire Delta System over a Four Wire Wye System or Visa Vera?

In the 4 wire delta or center tap delta there is usually limits of 5-7.5% of total kVA on the single phase loading. It was meant for control power for the 3 phase load only. I have found most do not get this and overload the center tap capacity. You can tell easily when you take off the cover and Center coil is cooked black and outside coils look good.
3-phase 4-wire wye: In the U ...

What are some other considerations that go into choosing a Three Wire Delta System rather than a Three Wire Wye System other than budget?

Basically, 3-wire 3-phase systems save one conductor, the neutral, in overhead construction.
In a service (600 volts and under) the source transformer winding is a delta or an open-delta. In California, if the voltage is 240V, then one of the corners is grounded. If it is 480V then it is ungrounded.

As a distribution system, the sou ...

Aircraft electrical components operate on many different voltages both AC and DC. However, most of the aircraft systems use 115 volts AC at 400 hertz or 28 volts DC. 26 volts AC is also used in some aircraft for lighting purposes, where the power is generated by a commutator which regulates the output voltage of 28 volts DC.Aircraft AC power, normally at a phase voltage of 115V, is generated by an alternator, g ...

Basically there are just two type earth fault and restricted earth fault.
An earth fault is a leakage of current between any conductor that normally carries current, that is the phase and neutral conductors, and the general mass of earth and anything connected to it anywhere downstream of the point within the system that the earth fault protection device is situated. The protective device for this type of fault is often referred to as an unrestricted earth fault device.

A res ...

Q: I heard that if we have a 3 phase induction motor constantly operating under 40% of rated power, we can reduce its losses using a Wye connection. But I can't find any reference of recommendation about that. So is it a practical solution to maintain energy efficiency? And is there any practical intelligent Wye-Delta switch?

The voltage across each winding drops by sqrt(3). So the torque-speed curve is reduced (by a factor of 3). The equilibrium speed is only slightly changed, but ...

There are different types of relays and each type has specific applications. It looks that you are looking for overcurrent setting calculations, as can be seen from mentioning plug setting and time setting multipliers. This is a typical protection scheme in distribution systems, the story is different at transmission levels.

There are many commercial software packages available that can be used to do the calculations, but again you need to build fundamental knowledge in order to in ...