Technically Specialized Solutions
Providing technical solutions to specialized problems....just ask us how

Here are a few of our most Frequently Asked Questions

1. Can I install a VFD on my current motor or do I have to change the motor?
Yes, contrary to popular belief you can install a VFD on an existing motor as long as the motor is in good health and is at least NEMA B rated.  To determine the health of the motor, take the amperage of the motor legs.  The amperage should not be greater than 3% from the highest to the lowest.

2. Can I use a single VFD to control more than 1 motor, like 2 motors for instance or do I have to buy another VFD?
Yes you can use a single drive to control up to 3 motors (depending on the VFD Manufacturer).  The drive has to be sized to match the FLA of both motors combined.

3. What is this electrical fluting that I keep hearing about and is there any type of fix?
Well there are varying opinions here, there are a lot of band aid type fixes out there, see our electrical fluting page

4. Ok so I hear that drives save money, how do they do it?
The horsepower is a relationship to the power drawn by the motor.  Basically if you reduce the speed of the motor by 20% you can see an energy savings of 48% (or 50% as most people state).  VFD's basically change the HP of the motor, thus using less kW.

5. How could 4 motors running at 50% speed on a drive use less energy than 2 motors running at full speed not on a drive on my cooling tower?
For this example, we will use a standard 40 hp motor.  Lets start with the 2 motors at full speed, each motor draws 29.8 kW for a total of 59.7 kW.  Now each motor running at 50% speed draws 3.7 kW each for a total of 14.95 kW for the 4 motors.  You can run all 4 motors at 79% speed (21% speed reduction) and draw the same energy as the 2 motors at full speed.

6. I recently put VFD's on my cooling tower, and my BMS vendor still has the tower stage up and down as it was before, is this correct?
Absolutely not.  This is a common problem amongst BMS vendors, they are stuck in the old days.  It's kind of like this - it's either they all run at the same speed or nothing runs.  The same hold true for fans (supply and return) as long as they share a common header.

7. Speaking of fans, if I have a common header and one of my drives fail, should I run it on bypass and manually reduce the speed of the other drives?
No, on a well controlled system you should not have to reduce the speed of the fans at all they will automatically compensate for the increased static pressure from the fan that is running on bypass, and if you choose not to run the one fan on bypass, the drives for the other fans should speed up.

8. What is the minimum speed that I should run my drive at?
Well that depends on the application - on our client drives, we set the minimum speed on the VFD to 20% or 12 Hz.  I know that on certain types of cooling tower there is a splash lubrication system and the minimum speed on these should be set to 25% or 15 Hz.  I would have this setting in the VFD, as some BMS vendors like to have control over this minimum, but if for any reason the BMS fails, no problems will be created.

9. Should I buy a drive with a bypass or can I get by without one?
This is kind of like should I get a car with a spare tire or should I not get a spare tire.  There are a lot factors governing the necessity of the bypass, first and foremost is always cost.  Sure you can save money by not getting a bypass, but you have to ask yourself a few questions.  First, is there redundancy if the drive fails (can I still make my condenser water temperature if I lose one cell on my cooling tower, or can I still make static pressure if I lose 1 fan).  Second, would be who is going to bypass the drive if it fails and how easily can it be done (a 200hp 460v VFD uses (3) 500 mcm wires, how are you going to splice these to get the drive running)

10. I have a mix of Magnetek, ABB, AC Tech, and Yaskawa drives, do you work on all of these, I was told by different vendors that they only work on 1 manufacturers drives.
Yes we work on them all, to us a drive is a drive, only the software changes, the basic principle stays the same.  We get a kick out of this when we hear that they only work on one manufacturers drive.  This is like the neighborhood mechanic telling you he only works on a certain type of car (Chevy, Ford, Honda, etc)

11.  I have old Magnetek drives and I was told by my vendor that Yaskawa (the company that bought out the Magnetek Drives Division) no longer has parts and that I should change out the drives, is this true.
No this is not true, you can still get parts from Yaskawa for all the series of drives.  We deal with numerous vendors to obtain parts we do not always rely on Yaskawa.  Our goal is customer service. Yaskawa sometimes has lengthy backorder on parts, how long should your drive be down while you wait.