Varying input voltage refrigerator testing application

[Jaime Rodriguez]

I am working on an application for refrigerator testing. One of the specs that we need to comply requires that we vary the input voltage, (ex. 127 VAC for a 120 VAC unit) through some sort of voltage regulator. The biggest unit we test has a 2 hp compressor with a max current draw of 18 amps. We would like to know what equipment we would need in order to accomplish this through a LabVIEW application that we are working on. We could do this through GPIB, serial, etc. Any help on this matter will be appreciated.

[RavensFan]

I would look at an AC motor controller.  They take an input voltage and restructure it to drive a motor at different voltages and frequencies.  They usually have serial interfaces so a PC can speak directly to it.  In your case, you didn't mention the need for different frequencies, so you can set it to be a constant 60Hz.  But there should be a drive parameter that would let you vary the output voltage.

You may need to have an input power to the drive that is higher than the highest voltage you want to put out.  For example, to put out 127VAC, you would need to put in at least 127 VAC to the drive.

[Jaime Rodriguez]

Do you know of ant specific one that might do the job???

[RavensFan]

We've used several different ones from Control Techniques.  www.controltechniques.com  such as the unidriveSP and and Commander SK.  I'm not sure which would be the best.

I must say though that we use them because we are a part of Emerson Electric Co. as well as they are.  However, even if we weren't, I'd still use them because I've been happy with their performance.

[Jaime Rodriguez]

I am sorry but I did not mention that these refrigerators are single phase 120 / 240 VAC. Emerson only works with 3 phase motors.

Any help in this regard??? 

[RavensFan]

You might be right.  I was think of one small 1.5 HP controller (Commander SE) we are using that is being powered by 1-phase 240 VAC supply.  So I was thinking the motor was 1-phase, but actually it does the voltage chopping to create a 3-phase supply to the motor.

It may be possible to still use one where you just use 1 phase relative to ground, but I'm not sure, and I'm not an electrical engineer to be able to tell how to do such a thing.  It may be worthwhile to ask them if such a thing can be done.  Or look around for some other motor speed controller manufactures that make a 1-phase motor controller.

I'm sorry, but I don't know where else to look or be of any help.

[Brian_Beal]

You might want to check with Georator or Xantrex.  They both offer solid-state power sources with adjustable outputs.

[johnsold]

It has been quite a few years, but I have used California Instruments AC power sources for clean adjustable power.

Lynn

[Jaime Rodriguez]

tHANKS a million for your responses.. .I am speaking to all your recommended suppliers..