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We know the equation kva= kw/power factor. When power factor reduces, kva increases. The substation authorities have to pay a penalty if demand indicator (kva) increases over an integrating period. How the maximum demand (kva) is being calculated in substations. Are there any ways to avoid load shedding of critical loads in substations if the maximum demand indicator goes over a maximum value when power factor is reduced?

In a Tr ...

This power inverter is designed for 12v DC, but also can be connected to 24v DC, my goal is 800 watt, strive to 1000 watt pure sine wave output. The inverter overall structure is, downside is a large cooling plate, upside is a power board with same size as the cooling plate, length 228mm, width 140mm. 4 power tubes of voltage boost portion, 4 power tubes of H-bridge and 4 TO220 packed fast diodes are screwed on the cooling plate ...

First of all, a DOL controlled motor may run in Fwd only, or in Fwd and Rev, depending upon the load and process (quad 1 or quad1 & quad 3 operation) - you simply switch it on/off via a contactor and it accelerates/decelerates between 0 and full speed, through its designed torque/slip curve. There will be no generation in these quads, the contactor is open, therefore the electrical supply to the motor windings is OFF and the motor will simply slow and stop in a load defined time (instanta ...

A soft starter is NOT a replacement for a VFD (variable frequency drive) if you have to start a high inertia load. A soft starter works by reducing the RMS value of the voltage supplied to the motor by delaying the firing of the output SCR's (or IGBT's etc.) until later in the half cycle after the zero crossing. To all intents and purposes, it is an oversized lamp dimmer that will reduce the motor starting torque (saves the mechanical drive) and ...

Situation
I have recently encountered a fairly unusual installation where a YNyn0 transformer has been used to supply a low voltage pump installation incorporating a large VFD.
The transformer was initially chosen to offset harmonic distortion with an adjacent Dyn11 supplying an identical VFD.
The transformer has been installed with the primary neutral connection floating in an effort to prevent zero sequence currents from causing nuisance tripping at the su ...

We were called in to replace an old imperial frame 180 kW motor on a circular saw because they needed a faster cutting speed. Shipping a motor of that size to a remote location was expensive, plus all the mounts and pulleys would have to be changed (imperial to metric and smaller frame size.). Instead we changed the VFD, the forced cooling fan and made some changes to the programmed cutting cycle.

With an older motor you often get more copper, and a lower efficiency. But you do get ...

Induction motor with squirrel cage rotor has two different speeds. The synchronous speed refers to the stator rotating magnetic field, which depends on the number of poles and frequency. The other speed is the rotor's. The rotor speed will be always slower than the stator speed, we call it slip. Without the slip, the squirrel cage induction motor doesn't have torque. Even without load the motor has slip. It increases with the load, according to the current x torque curves you can check it out ...

VFD and IMO are not going to be competitors in the same market. The benefits of VFD are various depending on the intended use. Bigger the motor (from kW to MW), bigger the benefit. They can act as soft starters therefore reducing the stress caused to the motor during the startup. With the VFD you do not go above nominal current (if you do not want).

VFD for fan and pump applications will considerably increase efficiency of the system as reducing 10% the top speed, the power absorbe ...

BLDC motors are usually in small capacity ratings, and it is universally adopted principle across word to use star connection (either internal or external) in small HP motors. Anyway, Star or delta connection matters only in case of motor with 6 leads and operating with star-delta starter, which is never a case with BLDC motor.

Star/Delta connection matters only when there are six leads and starter ...

Situation: Here is my current problem and was wondering if anyone had experience of the following:
Application - 260Kw submersible motors/pumps must be running up to full speed within 5-6 seconds of startup.

My proposal had always been to use a soft start until the pump manufacturer has stated that in order to provide sufficient cooling to the stator windings (using the sea water), it must be at full speed in 5-6 seconds.

I have been in touch with ...

Energy Management is a major part of Industry and understanding how much money it costs to operate electric motors in industry is a large part of that management. Electric Motors take up the major percentage of energy used in industry and even a small percentage drop can mean major savings.

When we go out and purchase a car, the first question most people ask is: "what is the fuel consumption"? In actual fact the cost of the fuel over a 7 year period is very low in comparison to th ...

If we define nominal torque, it's generated at the motors peak efficiency point, that being at the apex of rated voltage and Hz. The lower the RPM, the higher the nominal torque, but the higher the current. Then, nominal torque is basically what the motor can generate continuously at the peak efficiency point without overheating. To define using nominal torque at zero speed is better defined as stall torque, and not really applied in high torque starti ...

For someone who works with machines that are for large, heavy-duty industrial processes (like steel mills), the answer will be different than if they come from a background of moderate process requirements (pumps and fans) or precision processes (servo motors, actuators, etc).

From my perspective (which is the "large industrial" side of things): I work with designs that have continuous torque ratings that start at about 4500 lb.ft (6.1 x 10^3 N.m) and go up from there. The largest ...

First make sure the cause of the noise is not mechanical in nature (bearings, misalignment, worn bearings, lose hardware, lubrication, etc., etc.). If the cause is identified as being electrical in nature you can check some of these.

Is the motor rated for VFD service? Although you may be able to use a regular 3 phase AC motor with some VFD's, a regular 3 phase motor is not design to work with VFD's and thus will operate with higher electrical losses than a motor which is rated for ...

The function of a capacitor bank placed at an MCC panel is to provide reactive power to the inductive loads (improve power factor) and raise the voltage according to the system strength and capacitor bank size.

If the MCC loads also contain harmonic current distortion as is commonly produced by variable speed motor drive rectifiers, then a distortion problem can be produced should one of the principl ...

We are looking at an approx 90% + efficiency rating using asynchronous motors with the proper VFD's. With using regen instead of dynamic braking resistors, both in deceleration in traversal motions and in the overhauling effect of the load to the motor in lowering mode, the energy generated by the motor is channeled back to the line source, instead of being dissipated away as heat.


However, ...

The Buchholz relays I am used to dealing with have two levels, a Gas Alarm (Volume) and Gas Trip (Surge). They have a nitrogen injection port on the tank side of the Buchholz to inject to test each of these contacts, and a bleed port from the top of the Buchholz which allows for the nitrogen or fault-gasses to be captured for laboratory analysis.

Obviously an open flame is a low-tech way of determining if there are short-chain hydrocarbons present in the gas in the Buchholz, but if ...

All variable frequency drives using power electronics are essentially "frequency choppers". Either the VFD is a current-sourced inverter topology, or a voltage-sourced inverter topology. To obtain the desired output (usually defined as voltage at some specific frequency), the incoming signal gets "chopped" and rectified to produce a DC pulse, which is then inverted back produce a "sample" of a fraction of a sinusoidal waveform.

The sample can ...

The question was directed to single phase motor which it is surmised to be of induction type. Depending on the load characteristics, your motor could stall or overheat (or simply not start) if the frequency is not the one it was designed for at a given load. Three phase motor is not exactly the same as a single phase motor in speed-torque characteristics. Single phase motors are meticulously designed to have start-up torque through shaded pole or capacitor, etc. They can handle certain loads ...

Asynchronous motors are capable of developing significantly higher starting torque than synchronous motors. It has everything to do with the slip. Two pole motors are also an issue at start, due to a significantly lower starting torque capability than 4 or more pole motors.

An encoder of some type is typically used for hoisting applications when the hoist has no mechanical load brake in the gear case. Generally, when we build flux vector hoist controls, we employ 1024 PPR, 24 VDC, ...