# Can the output voltage of this variable frequency drive (VFD) be varied?

I am looking to buy a Cutler-Hammer "Adjustable Frequency Drive" AF91AGO BF25D. I’m a bit confused even after going through its datasheet. Can the output voltage of this VFD be varied from 0-230 V, or is it fixed between 220-230 V? I saw another VFD (a Schneider Electric "Altivar" ATV12H037F1) that says it can vary from 0-240 V, this got me confused.

Sorry, I haven’t used a VFD before. I’m looking to obtain this to get a 3 phase, 115 V, 400 Hz supply to power up some avionics.

• VFDs are intended to have an induction motor as a load. The voltage is varied depending on frequency and is usually based on an internal algorithm. You might be able to get it to work with a transformer or maybe two motors - one as a motor, the other as an alternator. Also note they expect the inductance of the motor to filter the waveform. Aug 13, 2022 at 3:36

The best thing to check when asking these questions are the manuals and datasheets.

Can the output voltage of this VFD be varied from 0-230V, or is it fixed between 220-230V?

On page 1-4 we have the same information you can see on the nameplate. The rated output voltage is 200-240 V, three-phase, with a note that indicates that this range is a function of the input voltage. So, no, the output voltage cannot be varied outside of those bounds.

We can also see from the nameplate and page 1-6 that the output frequency range is 0.5/1-360 Hz. Not quite 400 Hz.

I saw another VFD (a Schneider "Electric Altivar" ATV12H037F1) says it can vary from 0-240V, this got me confused.

The ATV12H037F1 may indeed be constructed differently. Again, check the datasheet to find that the rated motor voltage can be varied from 100 to 480 V, defaults to 230 V, but should not be set higher than the line voltage. The rated motor frequency can be adjusted from 10 to 400 Hz. Both of these are on page 57.

Now, the above is a bit moot because:

I’m looking to obtain this to get a 3 phase 115V, 400Hz supply to power up some avionics.

I would highly recommend against doing this. VFDs are not designed to supply a general power load or to be used as a power supply. The output voltage from a VFD is not sinusoidal, instead, it is a stepped PWM that relies on there being a rather large inductance attached at the load side. This is not something that I would want to connect to sensitive aircraft equipment.

115 V, 3P, 400 Hz power supplies are something that you can buy on the market.

• You can add smoothing chokes on the output of a VFD to filter out the carrier frequency, usually around 10-20 kHz. I have also connected a VFD to two step-down transformers to get 8-24 VAC at 60-240 Hz. This will work best with a simple V/f control algorithm that adjusts voltage proportional to frequency. Aug 18, 2022 at 20:38
• @PStechPaul -- neat! I have never seen that done before. However, once you're in for the VFD, reactors, breakers, transformers... wouldn't a standalone power supply be cheaper?
– user199402
Aug 18, 2022 at 20:59

I’m looking to obtain this to get a 3 phase, 115 V, 400 Hz supply to power up some avionics.

If that's for a professional use, get a proper avionics power supply. If the VFD fails or gets misconfigured - the latter is super-easy, it will damage avionics worth way, way more than a proper 400Hz power supply.

If it's for a hobby use, get three suitable audio amplifiers, connect them to regular 50/60Hz "power supply-use" step-up transformers (a step down connected in reverse), and feed them from a 3-phase 400Hz reference signal. You can generate it using PWM in most microcontrollers, or using built-in DAC, etc.

There are plenty of fairly small class-D single channel audio amplifier modules with relatively high output power (>100W), mains transformers are no big deal to get, and generating the reference signals is not hard either. It will be much, much safer than using a VFD, too, since the output voltages will be inherently isolated from mains.