variable speed drives

It's useful to warn engineers against taking decisions without any supporting facts and numbers, just taking for granted what salesmen say. When just connected to the grid, an induction motor will probably have more than necessary flux, because it will probably work below its nominal power. The assumption that one can exactly match the size of the motor to the application is unrealistic. The motor cannot be sized for exactly the required torque for many reasons, including the fact that sizes ...

First, what size of variable frequency drive (VFD) is being approached? When we speak about costs, remember that cost is quite different between a 10 MW VFD and a 7.5 kW VFD. Performances vary as well, in per unit basis and absolute value (kW).

There are also different types of VFDs for different types of motors, that is synchronous or induction for example. Therefore, evaluating case by case makes sense and other considerations along with the above mentioned also needs to be carr ...

Using a DOL system is an economic way to start a motor en by the way have cost saving, but for me the only way of really saving money according energy consume is variable frequency drive (VFD), for an easy reason, is that all the system size have a margin error in calculation and the load thermic load point is most of the time different of the real load on site, due to many reason.

I mean that using a VFD help to get the real needed load point of an application and by the way make ...

For the only reason that actually we have on the industrial market enough technology and tools to comply with all process using rotating machine, so actually just having a look to technology is not enough anymore.

And more than this if we build high efficiency product and we talk a lot all around the world of energy saving is not only for fun, but to push people working in technical business like ours to go a bit more deeper than just make something moving and more and more take c ...

I am in the sugar industry and our factories tend to be very close to nowhere. We have large energy demands which we meet with a renewable fuel but we do have "brown outs" and short duration "blackouts" aside from the total "blackout" situation. If this is not what you require, stop reading now.

We have recently started introducing "ride through" to many of our critical applications. If the factory is stopped it is very difficult to get going again and the losses are high. The mos ...

No device has an infinitely fast response to an input, so the rise and fall times are specified for each one. As the variable frequency drive signals increase in frequency and shorten in duration, more time proportionately is spent "in transition" rather than at one or the other power rails. While the device is in transition, it will need to dissipate additional energy as heat, and raise the operating temperature locally.

Pretty much all semi ...

Case: I have a VFD installed at my plant to run a 500 hp motor. Recently we had an incident of motor tripping on Ground Fault. The motor's insulation resistance was tested & the results showed that winding was grounded. After repair, the motor was again connected to the VFD & started but the VFD tripped the motor on "Inverter Ground Current". I checked the insulation resistance of motor & cable but the values were in Mega Ohms. I even checked the VFD physically to ensure that the ...

The power developed by Induction motor during idling time if wasted in power resistor used for braking is called dynamic braking resistor. Dynamic braking resistors are used to dissipate the power generated by the motors during dynamic braking. Typically, the variable frequency drive (VFD) will rectify the power back to a DC source and the resistors are cut into the dc link via a heavy-duty contactor. The power is then converted to heat in the braking resistor grids. These resistors must be a ...

The value of critical distance depends on the propagation voltage and output rise time so as much the value of propagation voltage the critical distance will be increases. Mostly variable frequency drives (VFDs have same critical length and it already mentioned in VFD manuals so there is no need to measure the critical distance as you can get information from your distributor or manufacturer of the VFD.

Some manufacturers of large variable frequency drives integrate output circuit ...

For large mills requiring variable speed, the wound rotor motor and SER drive are economical for a total rating of approximately 2MW to 16MW. Above 16MW, the gearless drive (cyclo-converter) is typically used because gearboxes and pinion gears reach their present limit in size. Around 2MW and below, the squirrel cage/VVVF drive is simple and cost effective.

Advantages of the wound rotor/SER drive are:

1. If the SER converter drive fa ...

Understanding the motor load is critical to specify a VFD. There are three basic types of load; constant torque, variable torque, and constant horsepower and you only need to know which you have. The machine defines it; the VFD difference is the amount of overload they allow. There are also options available for overhauling/regenerative loads.

PWM VFDs are still the predominate type and are simple t ...

Variable Frequency Drives convert AC to DC and then from the DC creates an output voltage at an adjustable frequency to run the load motor at whatever speed you want from 0 to 60 Hz. The voltage generally varies from 0 to full voltage as the speed goes from 0 to 60 Hz. They can also go above 60 Hz up to 400 Hz, but the torque falls off as the speed increases.

A VFD is a device that changes the frequency that an AC motor sees a ...

VFD means Variable Frequency Drive, by using VFD you can use AC motors on highly controlled way. VFDs slightly adjust frequency based on given parameters and AC motors are able to achieve even extreme options for example zero speed at max torque (brake operation mode). AC motors are much less sensitive than DC ones so using VFD and AC motors after SCR and DC motors is a really joy.

Applications of VFD are becoming very common and continually get benefits from it. Basically the app ...

Variable frequency drive (VFD) is a whole science and even a very broad deliberation here will not give you any good picture. I was teaching VFD course for one of the manufacturers and for an introductory session I talked for 8 hours, full course - 5 days and this is still just facts. Surely, you can buy 1HP VFD hook to 1HP motor and it is going to work regulating the speed by a pot on it. However, if you buy 4MW (that is 4 mega watts) VFD to run pil ...

Just a note of caution if you are going to use a variable frequency drive (VFD) on an existing motor it should be manufactured with at least Class F insulation and be rated for inverter power source. Because of the PWM (Pulse Width Modulated) waveform there is residual heating and most motors will go to 1.0 SF from 1.15 SF. There can also be issues relating to lead lengths in excess of 100 feet or more, output filtering may be required, ie. ...

A VFD is shortened for variable frequency drive it's a sort of AC drive which control the speed of the ac motors depending on frequency change. VFD is very useful in industry today, but much thought to the application must be taken. For example, if you are controlling motor speeds at or below 50% to 75% (and maintaining them in this range), you may want to consider changing motors to a different RPM. VFD produces harmonics that ca ...

What really happens with a variable frequency drive (VFD) / variable speed drive (VSD) and the actual frequency that is imposed on the electric motor terminals? For induction motors, it is never 0 Hz. For synchronous motors - it can be DC / 0 Hz - but this is only in the case of Permanent Magnet Synchronous machines, and motors with Wound Fields that have the ability to supply significant Current into the wound fields at standstill.

I am not going to discuss synchronous motors fur ...

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 ...

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 ...

Problem:
Pump type is a piston dosing pump with manual struck length adjustment with motor 3 phase 220 AC volt delta connection variable speed. We control it with a GK3000-2S0007 1 hp variable frequency drive (VFD) single phase 220 VAC to three phase output. We control the dose of the pump through the VFD with analog reference signal 4-20 mA which effect the frequency (V/F) which change the motor speed rpm. The problem is at low required dosing ...