Can a Variable Frequency Drive convert standard wall outlet (120V/15A/single phase) to ~220V 3 phase?

Question

In my workshop I have a device that requires 220V 3 phase power, with a requirement of up to 1.5kVA. In North America, my wall outlet provides ~120V/15A single phases.

(EDIT - my device can take +/- 10% voltage, so anywhere from 220V to 240V 3 phase is fine.)

Doing some research, I found devices like these, called 'Variable Frequency Drives' that seem to take this type of single phase input and give the 3 phase output desired:

https://www.mcmaster.com/variable-frequency-drives

I am a noob at electronics, and I just want to confirm if I could buy one of these VFDs to solve my problem as described. I guess I would get the 2 HP version to match approximately 1.5kVA.

Thank you for any help, and open to other suggestions if this won't work.

Answer 1

There are VFDs that will accept 115V single phase input and give you a 230V 3 phase output. They use what is called a "voltage doubler" front-end rectifier, meaning they rectify the 115VAC to approx. 165VDC, then put it through a circuit that doubles the DC to 330VDC, then the inverter section uses PWM to recreates an output that MOTORS react to as if it is 230VAC 3 phase. The key point however is MOTORS; this can ONLY be used for 3 phase AC induction motors, you cannot use the output as a general 3 phase power supply source. it is the inductive nature of the motor that allows the PWM to become a pseudo-sine wave. Without the motor, it's just pulsating DC that changes direction.

Then there is the size issue. On a 15A 115V circuit, you can actually only load it to 80% of that continuously, so 12A. The largest 115V input VFD is for a 1-1/2HP motor, but the INPUT CURRENT on the 115VAC side is actually 20A; too much for a standard 15A circuit and actually, too much for even a 20A circuit (80% rule means a 20A circuit is only good for 16A continuous). For that reason, MOST of the companies that sell a 115V input VFD limit it to 1HP, and even those require a 20A circuit (the NEC allows you to use a 20A breaker for a 15A outlet if you use 12ga wire).

Bottom line, if you have only a 15A 115V outlet, you cannot (legally) connect a device to it that requires 1.5kVA continuously, that is too much for that circuit regardless of what you put on it.

Answer 2

Knowing the cost of doubling line voltages for 3 phase from 120 to 240V, I think it would be better to install a 2nd line to get 120+120=240V service wire to hard wire the VFD and the variety of choices is better, at a much lower cost.

Selection

my pick

$275

The come with a fancy set of interfaces that don't have to be used but can add value to some operations.

There is also a variable torque version can drive up to 3Hp for the same size/cost unit as this 2Hp constant torque version.

Answer 3

With the luxury of not attempting to answer the question while it was so incomplete and misleading, I would say that you should not use a VFD. Using a VFD to power something that is essentially another VFD is asking for trouble.

I recommend that you consider:

1. Determine if the servo drive will accept single phase input.

2. If it will, see if you can get a 240 V outlet installed.

3. If installing a new line for 240 V is not attractive, investigate the methods for using two existing 120 V circuits.

4. Consider using a 120:240 V step-up transformer.

5. If the servo drive will not accept single phase, there is probably a way that is can be hacked to make it work. However that will probably require a level of assistance that you can not get here.

6. If you absolutely need 3-phase:

7. There are both electronic and rotary phase converters on the market.

8. There are hobby groups for metal working and perhaps other areas that have online plans for making phase converters.