vfds

I have a question regarding protecting a variable frequency drive (VFD). I have read that the important part to protect of the variable frequency drive is the active front end (prior to the IGBT's). I also am under the impression that the VFDs themselves protect the motors from faults. So my questions are as follows:

1. Do you need an overload to protect the motor? And if so do you put in on the PWM output side?
2. How should I protect the variable frequency drive and Motor? ...

Q: What will happen if shaft earthing brushes are not provided for VFD driven motor? Is it acceptable? Motor is of 50 hp, 415 V, and is at 200 m from VFD panel.

A: More than likely it will work just fine. Think of the shaft brushes as cheap insurance. They will make sure the bearings are protected from discharge current to equipment ground. On the other hand, the brushes will also ensure a long useful life from the motor by preventing eve ...

This question is a little more complex than it seems on the surface. Let's start with understanding the reason you believe you need to provide some form of braking in the first place. Do you need to stop very quickly under either normal or emergency stop conditions? Does your process need to be able to decelerate quickly when changing from a higher speed to a lower speed? If none of these conditions exist you may not need to provide any form of braking at all. The system friction and windage ...

The vast majority of variable frequency drives (VFDs) are the "voltage-source inverter" (VSI) type with a diode front-end. These non-regenerative VSI-type VFDs, do not contribute to upstream fault current as the input diodes block any current that might flow from the dc bus to the mains.

For regenerative VSI VFDs, the actual front-end regenerative circuit can be either transistors (IGBT, etc.) or thyristors. The VFD controls will respond very quickly. The controls will sense eithe ...

I have used variable frequency drives (VFDs) from a number of manufacturers over the years (ABB, Gozuk, Control Techniques, Emerson, to name a few), and I have not had specific failures with any of them. What I did do:

1) Spent a lot of time up front to size the VFD properly for the application.

2) Spent time up front to research the VFD product specified to be used for the application - in ...

Every engineer has good points about variable frequency drive (VFD) failure reasons. Some of the phenomenons occur more frequently and some are rarer.

The sizing of VFD is important. Also the application and demands of application should be studied carefully. In some case it might be better to use soft starter than use VFD. Thus VFD is suitable for wide range of applications, some parameters should be examined before installin ...

JOG - a small change in rotational position. A "jog" command is essentially an energy "pulse". A very quick ramp up and down of voltage and/or current is commanded with the idea that it will generate enough torque to overcome static friction and move the rotor some arbitrary fraction of a revolution. Since the duration and amplitude of the pulse are programmable, the resulting angle of the move is also variable. A drive train which contains large inertia components (either in the driven equip ...

As for the good performance of a well-controlled variable frequency drive (VFD) system tank capacity is not an issue, my own criteria is to dimension them as expansion tanks, to take water hammering, and expansion due to temperature raises -if pipes are exposed to the sun for e.g., or water heating tanks are in the line.

For domestic and small civilian uses, a bigger tank will prevent start-stop cycles due to small leakages, but this will highly depend on relationship between set ...

Continuous level control, using a level sensor, would allow for cost-savings if applied using a properly-sized variable frequency drive (VFD). The VFD would allow more consistent level control, improve reliability in not requiring a control contactor and decrease operational costs. Employing a non-contact level sensor will supply a feedback to the VFD and would allow the pump to ramp up/down as the inflow increases/decreases. If the level goes too low, you could put the motor in an off state ...

Most modern day variable frequency drives (VFD) will offer V/Hz control, sensorless Vector control and optionally closed loop control for full field orientation control method. The V/Hz control is retained for applications generally whereby a high torque speed or dynamic control is not required such as applications like centrifugal pumps and fans, or lightly loaded applications.

Although it can be argued that in modern Sensorless Vector VFDs the motor modeling and speed of the M ...

If the motor is designed to run in star a 380V 3-phase power supply, then it cannot be connected in delta on the 'same' supply. That would be the equivalent of applying 380 volt to 220v windings so clearly the motor would fail.

Note that in star, each winding gets root3 of the applied voltage (or 380/1.732) connecting in delta means that each winding get the phase-phase voltage EG 380V.

If the motor is rated at 380V - 'delta connected' then it could be connected in sta ...

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 ...

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 ...

Most of the users installed variable frequency drive (VFD) near the MCC because it's easy to maintain the system but there are some issue's which may happen due to placing the VFD near the MCC like there is a kind voltage reflection issue if the length of the cable is more than the critical length which may damage the motor.

In this case we need to follow instructions given in the user's manual supplied with the variable frequency drive. Generally following are recommended by manuf ...

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 ...

It is possible. However, UPS, VFD etc. manufacturer's follow the IEEE519 recommendations for the allowable I & V limits. Generally, the user must specify for the requirements of IEEE519. But, there will be other Non-Linear loads are not only Electronic Converters but also Ferromagnetic Devices e.g. Mag. Ballasts, Trafo's, Mag. Circuits etc. and Arcing Devices e.g. Arc Furnace, Fluo. Lights etc. These Non-Linear Loads produce Harmonics which are classified as Excursion and flow where there ...

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 ...