Help spec a vfd for compressor

[nandomart]

Im looking at purchasing a compressor with a 7.5hp 3 phase motor. I dont have three phase at my place, so Instead of buying a single phase motor Im considering a VFD. I found one with the specs below and Im hoping you guys can help decipher if this will work for my application..







Voltage (AC)
460 V

Phase
Three

Input Frequency
50/60 Hz

HP
15

kW
11

Amps
23

Efficiency1
97.4

Watt Loss2
342

Height
11.5 in

Width
4.92 in

Depth
9.49 in

NEMA 1 Kit
NEMA1LP4

Unit Size
M4

Weight
13.20 lbs


Factory Installed Keypad
Keypad

Enclosure Type
IP20/Open

Revision
1st Revision

Notes
Brake Chopper is included with 2HP drives

1 At rated load conditions
2 At rated load conditions


Environmental Conditions
Enclosure
IP20 (NEMA 1 with optional NEMA 1 kit)

Installation Location
Do not install in locations where product could be exposed to dust, corrosive gas, inflammable gas, oil mist, vapor, water drops or direct sunlight. There must be no salt in the atmosphere. Condensation must not be caused by sudden changes in temperature. For use at altitudes of 3280 ft. (1000M) or less without derating.

Ambient Temperature
-10 to +50 ºC

Ambient Humidity
5 to 95 % RH (non-condensing)

Vibration
1.0 g

Storage Temperature
-25 to 65 ºC


Standards
Approvals
CE, UL, cUL, and C-Tick
Suitable for use on a circuit capable of delivering not more than 100,000 rms symmetrical amperes for 230 V and 460 V.
WEEE and RoHS Compliant


Input Power Supply
Rated Input AC Voltage
200-240 Vac, 1-phase, 50-60 Hz, ± 10 % V
200-240 Vac, 3-phase, 50-60 Hz, ± 10 % V
380-480 Vac, 3-phase, 50-60 Hz, ± 10 % V

Max. Voltage Imbalance
3 % of rated supply voltage

True Power Factor
> 0.4 nominal at rated load

Displacement Power Factor
> 0.98

Switching on Input Power Supply
Maximum twice/minute

Environment According to EN60664-1
Overvoltage category III/pollution degree 2


Output
Rated Output Voltage
0-100 % of supply voltage

Output Frequency
0-200 Hz (Adv. Vector Control Plus Mode)
0-400 Hz (Volts/Hertz Mode)

Switching on Output
Unlimited

Accel/Decel Times
0.05 to 3600 s

Overload Current Rating
150 % of drive rated current for 1 minute


Control
Control Method
Sinusoidal PWM Control (V/Hz with torque vector control)

Switching Frequency Select
2 kHz
4 kHz
8 kHz
12 kHz
16 kHz

Operation Method
Keypad operation: Hand, Off, Auto
Digital Input: Programmable for Start/Stop, Forward/Reverse, Jog
Timer operation: Stop after predetermined time frame
Link operation: RS-485 Modbus RTU

Frequency Reference Setting
Up or Down buttons on keypad or external reference

Analog Input
Built in Potentiometer
0-10 Vdc analog input
4-20 ma analog input

Preset Speeds
8 presets via digital inputs

Link Operation
Drive RS-485 or Modbus RTU

Second Reference Setting
Switch from speed reference 1 to reference 2 via digital input

Trim Reference Setting
Available for speed reference offset via potentiometer, voltage input, or current input

Acceleration/Deceleration Time
0.05-3600 seconds (two acceleration and deceleration rates are selectable via digital inputs.
Acceleration and deceleration patterns can be selected from linear or S-curve

DC Injection Braking
Starting frequency: 0.0 to 400 Hz
Braking time: 0.0 to 60.0 seconds
Braking level: 0-150 % of rated current

Frequency Limit
0 to 400 Hz

Jump Frequency Control
2 jump (or skip) frequencies via parameter set to avoid mechanical vibration

Jogging Operation
Operation via On key or digital input (Fwd or Rev)

Auto-Restart After Power Failure
Restarts the drive without stopping after instantaneous power failure

Slip Compensation
Maintains motor at constant speed with load fluctuations

Energy Savings
Controls output voltage to minimize motor loss during constant speed operation

Start Mode Function
This functionality smoothly catches a spinning motor


Logic Controller (LC)
Logic Controller Events
Over 23 types of Programmable Events

Comparators
Array of 4 Comparators

Timers
Array of 3 Timers, adjustable from 0.0 to 3600 sec

Logic Rules
Array of 4 Boolean Logic Rules

Logic Controller States
Array of 20 Logic Controller Action States


Process Controller (PI)
Process CL Feedback Select
Analog input 1
Analog input 2
Local bus reference
No function
Pulse input

Process PI Control
Inverse
Normal

Process PI Anti Windup
Disabled
Enabled

Process PI Start Speed
0.0 to 200 Hz

Process PI Proportional Gain
0.00 to 10.00

Process PI Integral Gain
0.10 to 9999 s

Process PI Feed Forward Factor
0 to 400 %

On Reference Bandwidth
0 to 200 %


Indication
LEDs
Green - drive is on
Red - indicates an alarm
Yellow - indicates a warning

 

[454ragtop]

You're going about this all wrong. In the first place, what do you mean you don't have single phase power? You must have single phase power. To use that VFD, you'd need 460 volts, which I'm 99.99% sure you don't have. An air compressor is a poor application for a VFD, better off doing it right and getting a single phase motor.

 

[nandomart]

Changed it. I meant I don’t have three phase. Can you explain to me why I’m going bout this all wrong? From the reading I’ve done there are some benefits of running a vfd on a compressor. Also, I’ve read that a three phase vfd would work for the application I’m considering. From what I under stand you would need to double the hp rating of the vfd due to the derating that occurs when you run a three phase vfd on single phase power. My question is will the one I provide the specs off work with my motor.

 

[Packard V8]

From what I under stand you would need to double the hp rating of the vfd due to the derating that occurs when you run a three phase vfd on single phase power.

Are you sure it works like that? Yes, a three-phase motor started via a static converter and run on single phase will only produce 2/3 rated power. AFAIK, the VFD produces full rated power output.

From the reading I’ve done there are some benefits of running a vfd on a compressor.

As they say, "Your opinions and results may differ," but most of what we've seen shared here do not encourage using a VFD on a compressor motor.

jack vines

 

[manwithtools]

Are you sure it works like that? Yes, a three-phase motor started via a static converter and run on single phase will only produce 2/3 rated power. AFAIK, the VFD produces full rated power output.
As they say, "Your opinions and results may differ," but most of what we've seen shared here do not encourage using a VFD on a compressor motor.

jack vines

Single phase input to a three phase VFD does require derating of the VFD rated HP by approx. 50%. Caveat - there are single phase input VFD's available that don't require derating up to about 3hp .

Anything larger than 3hp will typically will be three phase input designs that require derating when supplied with single phase.

 

[matt_i]

There's some conflict in specs due to the opening line of "460vac" and then later it mentions "200-240" and 380-480 vac input, although maybe that's cryptically telling you that +/- 10% of nominal input voltage is acceptable and not that its auto-ranging input (the latter would be very rare)

I would want to call/email a person before pushing the "buy" on that one. If the opening line was 240vac input then I wouldn't have this question.

Also you have to read the manual enough to setup a 2-wire start/stop setup and redo the pressure switch to be on low voltage, the VFD itself has a weak DC power supply in it (typically) to feed various inputs.

 

[454ragtop]

That's a 460 volt VFD, do you have 460 volt power? I still think a VFD is a poor choice for a compressor, but whatever.

 

[laser3kw]

That's a 460 volt VFD, do you have 460 volt power? I still think a VFD is a poor choice for a compressor, but whatever.

is the 460v motor dual voltage? If it is then rewire for 230v 3phase and get a 230v vfd.
What ever input the vfd is designed for is the maximum voltage you will get on the output. 240 in 240 out. You can not run a 460v on 240 (and get the rated performance).
Better yet - save money and hassle / time - get a 7.5 hp single phase motor.

 

[MattT]

There's some conflict in specs due to the opening line of "460vac" and then later it mentions "200-240" and 380-480 vac input, although maybe that's cryptically telling you that +/- 10% of nominal input voltage is acceptable and not that its auto-ranging input (the latter would be very rare)

Looks like the OP cut and pasted specs that included the 200v class and 400v class voltages. I've never seen an "auto ranging" drive that'll run on 200v and 400v.

Assuming the specific drive the OP is talking about is 400v class no it will not work with 240v input. Might be possible to run it with a transformer to step the 240v up to 480v. That's if the drive will run with single phase input and generally falls into the more trouble than it's worth category.

 

[nandomart]

Thanks guys I appreciate the feedback. It appears that I wasnt doing the right research regarding VFDs and compressors. I went back yesterday and found threads on not using them with compressors.

Is that still the consensus? I mostly wanted to use the slow start funtion of the vfd on the compressor start up....


I know getting a single phase motor is probably the easiest way...but if there is another option that allows me more control of what I have i would like to pursue that if its a viable option

is this a viable option? If so would the drive below be adequate? It would be the 230v one that I am looking at....

 

[hsvtoolfool]

How about a solid state phase converter instead? A compressor motor doesn't need the "features" of a VFD, just lots of clean, brute 3-phase power...

Phase Perfect PT-330 10HP rated

The outdoor model allows you to mount the converter outside at your main box, run the 3P wires through a breaker box, then directly to your compressor. Or you can run 2P to the indoor model next to the compressor.

Just some ideas.

 

[Firebrick43]

Thanks guys I appreciate the feedback. It appears that I wasnt doing the right research regarding VFDs and compressors. I went back yesterday and found threads on not using them with compressors.

Is that still the consensus? I mostly wanted to use the slow start funtion of the vfd on the compressor start up....


I know getting a single phase motor is probably the easiest way...but if there is another option that allows me more control of what I have i would like to pursue that if its a viable option

is this a viable option? If so would the drive below be adequate? It would be the 230v one that I am looking at....

You have confused us all and still have not cleared it it. Is your motor 480v???? Better yet take a pic of the name plate.

If you motor can not be rewired to 240v you can not use a Vfd to make it work period. While there are a few fractional hp vfd's that can step up 120 to 240 most are voltage in/ voltage out. While the VFD maybe multi voltage input you can not input 240 and get 480 out.

Also be aware that while a Vfd could help "soft start" motors, most air compressor pumps are designed to turn a mininimum rpm to provide proper lubrication. You can not go below this rpm to get quieter operating or you risk rod bearing failure.

 

[matt_i]

How about a solid state phase converter instead? A compressor motor doesn't need the "features" of a VFD, just lots of clean, brute 3-phase power...

Phase Perfect PT-330 10HP rated

The outdoor model allows you to mount the converter outside at your main box, run the 3P wires through a breaker box, then directly to your compressor. Or you can run 2P to the indoor model next to the compressor.

Just some ideas.

Phase Perfect is north of $5k last I checked....which is OK if you have the right application, its potentially portable anywhere one could move but its generally cost competitive with true utility 3ph.

 

[stonesfan68]

You can use a VFD on a reciprocating compressor but as Firebrick43 noted you need to operate the compressor above the minimum speed so as to keep the machine lubricated and cooled properly. The compressor manufacturer can give you the min and max speeds of the compressor.

You might also have to look at installing a pressure transducer and using it to control the VFD as opposed to the pressure switch that came with the compressor.

It might just be easier and less costly to get a single-phase motor, pressure switch and mag starter and convert the machine to single phase operation.

 

[bsaint]

What about just a rotary phase converter but at that point you can just buy a single phase motor.

For a recip compressor, I wouldnt run a vfd.

 

[manwithtools]

You can use a VFD on a reciprocating compressor but as Firebrick43 noted you need to operate the compressor above the minimum speed so as to keep the machine lubricated and cooled properly. The compressor manufacturer can give you the min and max speeds of the compressor.

You might also have to look at installing a pressure transducer and using it to control the VFD as opposed to the pressure switch that came with the compressor.

It might just be easier and less costly to get a single-phase motor, pressure switch and mag starter and convert the machine to single phase operation.

Why a pressure transducer? A VFD will start and stop with a 2 wire control circuit from a pressure switch just fine.

 

[nandomart]

You have confused us all and still have not cleared it it. Is your motor 480v???? Better yet take a pic of the name plate.

If you motor can not be rewired to 240v you can not use a Vfd to make it work period. While there are a few fractional hp vfd's that can step up 120 to 240 most are voltage in/ voltage out. While the VFD maybe multi voltage input you can not input 240 and get 480 out.

Also be aware that while a Vfd could help "soft start" motors, most air compressor pumps are designed to turn a mininimum rpm to provide proper lubrication. You can not go below this rpm to get quieter operating or you risk rod bearing failure.

I’m confused as well, the nameplate is and has been attached to the thread since I started it. Can you not see it?

 

[laser3kw]

Thanks guys I appreciate the feedback. It appears that I wasnt doing the right research regarding VFDs and compressors. I went back yesterday and found threads on not using them with compressors.

Is that still the consensus? I mostly wanted to use the slow start funtion of the vfd on the compressor start up....


I know getting a single phase motor is probably the easiest way...but if there is another option that allows me more control of what I have i would like to pursue that if its a viable option

is this a viable option? If so would the drive below be adequate? It would be the 230v one that I am looking at....

the spec sheet states capacity "(input) -230v single phase 1/8hp up to 3hp
so, no it won't work for 7.5hp
double down if your compressor motor is 460v 3 phase to boot.

 

[marinusdees]

the spec sheet states capacity "(input) -230v single phase 1/8hp up to 3hp
so, no it won't work for 7.5hp
double down if your compressor motor is 460v 3 phase to boot.

Compressors don't like "man made" three phase. Just the way it is.

 

[CGT80]

If you can get a 15+ hp three phase motor for less money than a 7.5 hp single phase, then it may work to do a rotary phase converter. The downside, is that it will have to be running when the compressor is ready to cycle.


Most compressors will run on two or 3 different HP motors and you may be able to run a 5hp single phase motor with less air output, if you chose to do so. They run slow and quiet with the smaller motors. Mine has a 5hp motor but the pulley was not the right size to spin it fast enough for full output (still fast enough for proper lubrication though, and it was very quiet).


Others have stated that their power companies demand they check with them before running any motors over 5hp as sometimes the supply is not suited for 7.5 and larger motors.


The motor on my compressor is an old 5hp baldor that has a nameplate amperage of 28.5 at 240v, but it pulls 169 amps to start and will dim the lights in the house and other garage.......maybe the neighbors house depending on the transformer and supply from the power company.


I have read many of these threads and it always ends up being best to use a single phase motor, although it doesn't mean that is the only way.

 

[hsvtoolfool]

Phase Perfect is north of $5k last I checked....

About $3K for the 10HP model adequate for a 7.5HP compressor motor.

Compressors don't like "man made" three phase. Just the way it is.

Only true for small, rotary phase converters. Phase Perfect solid state phase converters are fine for use with large motors including CNC machines.

 

[sberry]

2 5hp comps will make 40 cfm. A couple cheap 7.5 will make north of 50. If I was working g on cars would want a 5 or better for boxy and paint. I might be tempted to get 5 and 7.5, the big one wouldn't need to be great quality, just a boost for blasting.
This might even all be done with a 7.5, you gonna white blast the whole car? I can make more, I have big tanks, use a little smaller jet and I blast a long time with a 3 and a 5, .
I have 200# of sand.

 

[930dreamer]

You could build a phase converter cheaply and I run my compressor from my 10hp phase converter.

 

[laser3kw]

You could build a phase converter cheaply and I run my compressor from my 10hp phase converter.

I assume it's the compressor in your avatar?
Is the phase converter over sized for the compressor or is the compressor a 10hp?