ac drives

Variable frequency drive (VFD) operation with voltage and frequency control of the induction motor was acceptable for most applications. There were certain machines that DC motor control had some technical advantage. The VFD needed more intelligence to know the true load of the motor. An AC machine requires a magnetizing current to operate at no load. This current is not actually a lot of power, but looks like the induction motor always has 20 to 30% load. The DC machine load on the armature ...

Variable Frequency Drive, in short VFD, it can be called VVVF drive, variable voltage and variable frequency to change this from sinusoidal AC, the VFD changes the AC to DC first then DC to AC by using IGBT, this is done by firing IGBT very fast (carrier frequency), so this output is not sinusoidal.

If you want to know how does a VFD work, you should hit up Wikipedia or Google it, lots of articles out there. If you're wondering about how to use a VFD, there are numerous considerati ...

I would certainly say that thyristors are indeed extremely robust. Many IGBTs are designed to deliberealy limit the max current they can supply to limit short circuit currents and then allow a slower ("soft") turn off within the 5-10us s/c withstand time. So if you want very high peak to average current rating it may be this deliberate thing that is working against you.

Thyristors are 4-layer devices with two sources of carriers in difference with IGBTs. They operate at higher pla ...

An Active Front End (AFE) Drive installation where shutting off the filter would also shutoff the variable frequency drive (VFD). This is truly a serious and widespread problem that the AFE Drive manufacturers don't want anyone to know about. In fact, they actively promote their AFE 'low harmonic drives' as the ultimate solution. I chuckle when I watch one elaborate video produced by an AFE drive manufacturer that properly highlig ...

If the variable frequency drive (VFD) has a load of 1000KW, then the low frequency impedance must be fairly low to prevent excessive voltage drop. The problem is what the high frequency impedance looks like and whether there are any local supply resonances in the KHz range.

We see a lot of problems on the power supply with common mode, often coming from the output of poorly installed VFDs. Issues due to active front end and actives filters can be so much worse. It is both equipmen ...

High inertia loads present some challenges in both mechanically and from a control standpoint. Suppose the load is a "cement block". We could use a better description as to how this "cement block" is being put into rotation, what the inertia value is, what the speed of rotation is, and mechanically how the proposed motor would be connected to this load. Will it be directly connected? If so, what type of coupling is being considered? If there is a gear reducer, what is the type and gear ratio? ...

I don't even own a copy of IEEE 1566, but I note that its abstract defines it as a "standard for performance of adjustable speed drives rated 375 kW and larger." What do you call a 200kW drive? I have, however, worked in this field for 28 years. I'll concur with the complaint that words are used imprecisely, but that's the way life is. Had you said "adjustable speed AC drive"? I would say they and VFDs were the same thing, but simply "adjustable speed drive"? No, sorry.

As for your ...

I think there are a few more differences between different variable frequency drive (VFD) designs. For example: I've used VFDs that never use output load reactors, and can go, depending on the VFD model, 300 to 1000 Ft between the VFD and motor unaided. To exceed that distance, they use an RFI filter. Not tooting a horn, but pointing out one of the manufacturer's capabilities versus others, with respect to wanting to define the application as thoroughly as possible before taking on system des ...

In variable speed drive (VSD) systems, both AC and DC, the first stage of power conversion is from AC to DC. In a DC drive, it's the only stage - from fixed AC to variable DC. In an AC drive there are two additional stages: filtration and inversion back to AC.

The simplest converter is a full-wave diode bridge, which converts the incoming AC to a fixed DC voltage. This isn't useful in a DC drive, but works fine for AC variable frequency drive (VFD). Standard industrial drives - bot ...

If you talk to someone in variable frequency drives (VFD) sales, they will often tell you that there is no place for a soft starter because the VFD reduces the current more than a soft starter and the VFD saves energy, but in reality there is definitely a place for both of them. If you need to vary the speed of the driven load, then a VFD is definitely the choice. If you are looking to reduce the starting current and the starting torque of an induction motor, then a soft starter can be select ...

In simplest terms, the variable frequency drive (VFD) starts at zero hertz (Hz) and can run there indefinitely. I can make such a bold statement because at that frequency, and with the motor stationary, there is only magnetizing current being taken through the semiconductors. The variable frequency drive normal cooling system can disperse the heat that would be generated in this situation.

The motor in this case is likely one of two types; Induction or Permanent Magnet (PM). We al ...

A 12 pulse variable frequency drive (VFD) will develop a harmonic signature with high magnitudes on the 11th and 13th order. The good thing is the typical harmonic signature exponentially falls off as the order goes up. This is the reason that an 18 pulse VFD will have less harmonics than a 12 pulse VFD and so on and so forth. Another advantage is the DC buss will have less distortion when a multi-pulse front end is used. Most medium voltage VFD comes standard with 24 or 36 pulse front ends. ...

Inverters can be adapted from stall right up to CHP ranges, only design limits are feedback device and proper cooling aspects to the machine load profile. Some applications require extended low speed performance. Normally the variable frequency drive (VFD) supplier indicates speed range capability based on type of VFD and feedback device required.

There may be some confusion between frequency and motor speed.
Open loop, typical speed regulation is plus or min ...

When a motor power is stated, it is always the mechanical power, shaft power i.e. NOT the input electrical power.

Variable frequency drives (VFD) are also (mostly) rated in terms of kW albeit it's wrong. Because VFD output is electrical (not mechanical). Mechanical power (i.e. motor shaft power) is always "active" power, where in electricity we also have reactive (doing nothing but losses) power. The apparent (total) power (stated in terms of ...

Variable frequency drive (VFD), also called frequency inverter, variable speed drive (VSD), adjustable frequency drive (AFD). This article is about the basic guide of how to select a VFD.

The correct selection of the variable frequency drive (VFD) is critical for the normal operation of the mechanical equipment electrical control system. To choose the best suitable VFD, we need to know the specified machinery type, the load torque characteristics, speed adjusting range, static spe ...