VFD external control of fan

[titan1021]

I've install (3) WEG CW300 VFD's in a cabinet and need to add a cooling fan to the enclosure. While I don't normally work with VFD's I didn't want to send a long time client elsewhere for this project. I did my homework and have everything up and running well, except that I can't find much information on using the SPDT controls for an external device.
What I plan to do is install a 4" cooling fan in the side of the enclosure that will come ON and run while one of the VFD's is in use. They use all 3 at the same time so any of the 3 will work. I can't find anything with the basic wiring from the digital inputs and or outputs, or anything about how to accomplish this.
Do I need to supply control voltage to one of the inputs on the VFD?

Thank you

 

[Saturn_Europa]

The way I would do it is wire 24v + at terminal 11. Then wire terminal 12 to A1 of an interposing relay. Then break fan power through the interposing relay.

 

[TwoBlocked]

Here's the on line manual, in case others want to have a look. I believe the OP already has it:

https://static.weg.net/medias/downloadcenter/h01/hd8/WEG-CFW300-user-manual-10003325037-en-es-pt.pdf

Yes, terminals 11 and 12 will do it. connect all three sets on the drives in parallel. (11&11&11, 12&12&12)

As S_A said:
PWR+ to 11
12 to A1 on an interposing relay
A2 to PWR- on the interposing relay
Then operated the fan using Comm and NO on the interposing relay like you would a switch

As to the voltage of PWR+ and PWR-, first it needs to be the same as the coil for the interposing relay. I wouldn't try to use any @$VDC power off the drives. Instead a control transformer from the main power coming in to pull in the relay and operate the fan. Probably 120VAC. Remember to ground X2 on the secondary of the control transformer and fuse the xfrmr properly.

I did not dig deep enough into the manual to see if the default setting for the Digital Output is to energize when the drive is running. Usually is, but might energize when there is a fault. You might have to set a parameter.

 

[petersonra]

Best bet is to just put the fans on a thermostat. It's a good bet that most of the time when the VFDs are running they won't generate enough heat to require any external cooling.

By the way, a 4-in fan will probably not be adequate for the worst case conditions. You need to look at how much heat is going to be generated to figure out how much air is required to get rid of the heat in the worst case.

A 4-in fan just won't push much air.

 

[Jraef]

I would never use the on-board 24VDC for any external device. It is there to provide power for the INPUTS only, it likely has a VERY low capacity, maybe 10s of milliamps, but certainly not enough to operate a fan.

You need an external power source for your fan. If you want it to come on via any one of the VFDs, have the VFD output relays operate another relay (an "interposing relay") that is rated for the fan watts, then put your external power for the fan through that relay contact and put the VFD relay contacts in parallel to the interposing relay coil.

Or better yet, as Bob says, leave the VFD relays out of it and make it super simple by just putting a line voltage (for the control power you bring in for the fan) thermostat on the fan circuit. Set the t-stat at about 85F. Here's an example, it will cost you less than the relay to do it the other way.

 

[titan1021]

Best bet is to just put the fans on a thermostat. It's a good bet that most of the time when the VFDs are running they won't generate enough heat to require any external cooling.

By the way, a 4-in fan will probably not be adequate for the worst case conditions. You need to look at how much heat is going to be generated to figure out how much air is required to get rid of the heat in the worst case.

A 4-in fan just won't push much air.

The fan on a thermostat is a great idea! Simple and adequate, I was overcomplicating this. I have the 3 VFD's in a 18x12x8 enclosure while its not getting super hot, it does get fairly warm at the top of the enclosure. It seems like a little ventilation would be a good idea.
Thanks for the advice!

 

[garbo]

I worked & PM'ed VFD in cabinets that only used a thermostat at top of cabinet to run exhaust fan when temperature was above maybe 90 degrees. Of course the largest drive seller in the USA ( backward hard to deal with ABB ) would have cooling fans running 24/7 in 6 by 6 & 6 by 8' 100 to 200 HP 18 pulse drives cabinets. Only problem with that is some of these drives supply power to chillers that do not run all winter. They did not like to turn off 480 volt disconnect.becsuse they liked to run pumps every week to check pump seals. So constantly running fans pulled in dirty air year round and had to blow out & wash inlet filters every month. My company did not want me to install a thermostat so fans did not run all winter.

 

[tom baker]

Hoffman has DIN mounted T Stats, and information on calculating cooling needs. Cool air is denser than warm air,have the fan push air into the cabinet with louvered at the top. I used to use Hoffman muffin fans but found out a better product it may been WEG? One project had an outdoor cabinet about 500 cu ft, used 2 fans staged by T stats.

 

[tom baker]

Rittal was the company I used for cabinet ventilation. Hoffman fans were to noisy in our outdoor cabinets