Changing the motor on the drive

Hello everyone,
I have an application where I would like to make frequent changes of my motor without changing my sensorless frequency drive.

Is it possible to run a 1/8 Hp or 1/4 Hp motor on a 1 Hp drive? If yes, how easy is it to pass from a 1 Hp motor to a 1/8 Hp motor? Do I need to re-program the whole drive? Can I get away with a small change in the program? Is it dependent on the drive company? Will it hurt the drive or reduce its life?

Thanks in advanced for all your help,
Luc

Types of drives

Hello everyone,
I have a few questions on the different types of drives. I was told that the best drive for my application was a sensorless vector since I need a drive that can keep the same amount of torque at very low frequencies.

1) Can someone explain to me what is the difference between a sensorless vector, a V/Hz, and a flux vector control drive? I read the explanation on this site between the V/Hz and the vector drive. They are probably taking about the same things but with different terms.

2) The 115 V, single phase VFD that I looked at don't have any internal or optional filters. Is this because there is a transformer in the drive and there is less RFI/EMI or because the manufacturer just don't bother about the interference?

Thanks for your help,
Luc Landry

EMC filtering

Hello everyone,
Can someone explain what is the EMC filter? Is is EMI, RFI, or harmonics filtering?
thanks,
Luc

Is filtering necessary

Hello everyone,
I am looking for two small variable frequency drive to put on a molding machine. We would like to have your opinions.

1) How much would it cost for a good frequency drive of about 1 hp that functions on 120 Vac or 240 Vac 1 phase with a nema 4x enclosure?

2) Is it necessary to have a filter of some kind to prevent harmonics distortions?

3) When we buy a drive do they usually come with a filter?

4) What type of filter is usually recommended?

Thanks for your help,
Luc Landry
Canada

Burnt capacitor problem

Hello everyone,

I am new to this forum. I would like some help on determining the cause of a capacitor that burnt out in one of our buildings.

The capacitor was installed less then 10 years ago in the electrical room of the building by the local power compagny when they removed one of the meters (probably the KVA meter). It is a 30 KVAR, 28.9 Amps, 600 Volts, 3 phase from Nokia company distributed by Gentec. At the front end of the capacitor we have a 3 phase switch fused at 30 amps. The non-linear loads in the building are the transformers, a few small motors for ventilation situated on the roof, fluorescent lighting, some household electronics, and a 5 hp motor for the elevator. The 600 V, 3 phase motor and its soft starter controller are situated in a small room on the roof of the building. The building is 4 stories high. The hole building is heated using electricity. Also, we have an emergency generator that can supply the building.

Last week we had some problems with our elevator. It turned out that the small emergency battery of the controller, in the soft starter, needed to be changed. When we were trying to solve the elevator problem, we decided to look at the capacitor bank and we found out that the 3 fuses for the switch were burnt. We replaced the fuses and at some time during the day one of the fuse was burned again. The fuse had melted and the capacitor was smoking. We shut off the switch and called the electrician witch confirmed that the capacitor was burned out.

Since there is no alarm to indicate when the fuses burn out the first time we don't really know how long it was since they were burned out. Was it a week or months?

Here are my questions:
1. Was it necessary to have a capacitor bank in this building? Does the power factor really needs to be corrected?

2. What would be the cause of the blown out capacitor bank? Such capacitors usually can last from 20 to 50 years. Is it normal that it burn out after 8 to 9 years of operation? Is it common to have manufacturer's defects?

3. Do you think that the equipment of the elevator had any influence on the capacitor blowing out?

4. Is it possible that the capacitors burnt out because of harmonics?


Thanks for your help,

Luc
in Lac-Etchemin, Canada