[HillBilly]

This is the second time I have encounter this application and both times I have been told it doubles the horsepower of the motor. Does anyone know the theory behind this?

I am from the old school where the iron in the motor determined the horsepower.

Thanks Darek

[Eldon_Joh]

if you run the motor at double its nameplate rpm and keep the same volts per hz then yes.

but it won't be as efficient, due to windage losses mostly. might cut the fan blades down to compensate, or remove them and replace with a fan and a thermocouple

[mactec54]

This is the second time I have encounter this application and both times I have been told it doubles the horsepower of the motor. Does anyone know the theory behind this?

I am from the old school where the iron in the motor determined the horsepower.

Thanks Darek

One question are you running 480v into the 480v VFD ??

Can this double the Hp No it can't, all you will see mostly is smoke if you run the 240v motor on 480v, this can take a few minutes or a few seconds, depending on the quality of the motor construction

If the VFD is 480v and you somehow have got it to run on 240v, without a low voltage alarm, then it would run the 240v motor at a lower speed than normal, as the VFD Buss voltage will not reach the correct voltage to run the 240v motor at it's rated RPM, it will also have less Hp than if it was running on a 240v VFD

[HillBilly]

The VFD is definitely on 480 and the motor is wired 220. No smoke the VFD limits the current to the motor rating. The power is just PWM'ed from a highet DC bus voltage. Thats where inverter duty motors come in (better insulation).

They have done just as you suggest Eldon_Joh.

[mactec54]

The VFD is definitely on 480 and the motor is wired 220. No smoke the VFD limits the current to the motor rating. The power is just PWM'ed from a highet DC bus voltage. Thats where inverter duty motors come in (better insulation).

The VFD does not limit the current, you have to set the max current draw, Yes that is what I said it will depend on the quality of the motor build, but it is not designed to run at such a high buss voltage,even Inverter duty will only buy you more time, before it fails, not even the manufacture would recommend that you do this, they will tell you the same as what I have

[HillBilly]

The VFD does not limit the current, you have to set the max current draw

What do you think the VFD does with this setting?

[HillBilly]

This is on a 5 axis Cincinnati profiler. It has been running this way 4 years I know of.

[mactec54]

This is on a 5 axis Cincinnati profiler. It has been running this way 4 years I know of.

Without you yourself having hands on, with the wiring of this motor, it most likely is a 240v/ 480v rated motor, and someone is just BSing you,it would not have lasted that long if it was not

It would also be running at 60Hz for this application

480v x 1.414=678 bus voltage

240v x 1.414=339 bus voltage

You would need to look under the terminal cover of the motor,to see how it is wired, this will tell you, what's going on, they are playing games with you

[HillBilly]

Here is the motor tag. The motor is wired 220 with 3 wires coming out (no high volt option).

The motor is allowed to run up to 120hz and the VFD is set to 240hz base speed to achieve the proper V per Hz.

I am sure of all this hands on.

[HillBilly]

Another note: The 220V motor is a 30hp but the 480V drive is 60hp to be able to supply the current the lower voltage winding is expecting.

[mactec54]

Another note: The 220V motor is a 30hp but the 480V drive is 60hp to be able to supply the current the lower voltage winding is expecting.

It does not matter how big the drive is bigger the better, is always good, it just means that the electronics in side the VFD can stand more abuse

Keep dreaming 240Hz base speed

It can still be wired for 480v most 3ph motors this size have this option even though the nameplate says it's 220v

Here is the spec for your GE motor

Motor primary use General Purpose - Premium Efficiency
Horsepower 30
RPM 1800
Rotation Reversible
Frame size 286T
Enclosure type TEFC
Mounting Foot
Connection box Side
Shaft diameter (in) 1.88
Shaft type Smooth shaft w/ 0.5 x 0.5 key
Shaft height (from base) (in) 7
Overall length (in) 28.4
Overall height (in) 0
Bearings Ball bearings
Frame material Cast iron
Electrical Specifications:
Phase Three
kW 22.37
Voltage 230/460
Amperage (full load) 71.8
Frequency (Hz) 60
Duty cycle Continuous-use rated
Full load efficiency (%) 93.6
Inverter rated Yes

[HillBilly]

Your specs say foot mount but this is definitely a face mount motor.

The only way you can change the voltage of this motor is to lift the winding.

Like I said three wires in the pecker head.

[mactec54]

Your specs say foot mount but this is definitely a face mount motor.

The only way you can change the voltage of this motor is to lift the winding.

Like I said three wires in the pecker head.

Nothing changes just a different part # they still have the dual voltage rating option, they were mostly used as pump motors so are rated as heavy duty as well

Electrical Specifications:
Phase Three
kW 22.37
Voltage 230/460
Amperage (full load) 76.2
Frequency (Hz) 60
Service factor 1.15
Duty cycle Continuous-use rated
Full load efficiency (%) 91
Inverter rated Yes
Face mount Specifications:
Face type P-base
Bolt circle diameter (centerline) (in) 9.13
Number of holes 4
Integrated base No

[Eldon_Joh]

why the 240hz base speed? seems to me it should be 120hz.. you would be delivering 480v into the motor at 120hz.

or do you have a 960v vfd.

[HillBilly]

You may be right on the 120hz base Eldon_Joh. My 240hz base would only achieve the 30hp at 120hz operating frequency if I understand correctly.

[mactec54]

why the 240hz base speed? seems to me it should be 120hz.. you would be delivering 480v into the motor at 120hz.

or do you have a 960v vfd.

The Base Frequency setting can never be set at 120Hz, the nameplate Frequency setting is, 60Hz this is always the Base setting,for any VFD setup the 121.3 Hertz is the Max that this motor is rated for, this is the max Hertz setting that this motor can be set at

It is on the Nameplate if you look closely

A standard 4 Pole motor like this is normally rated at 90Hz max, but because this is an inverter duty motor it can take a little more punishment (121.3 Hz Max ) at 72 amps

[HillBilly]

I'm not sure about all that. But I had my eureka moment. The motor actually is 30hp at 60hz. But since it's constant torque variable horsepower up to the base speed (120hz in this case) the motors achieves 60 hp at 120hz.

[mactec54]

I'm not sure about all that. But I had my eureka moment. The motor actually is 30hp at 60hz. But since it's constant torque variable horsepower up to the base speed (120hz in this case) the motors achieves 60 hp at 120hz.

That's some eureka moment, I guess you believe in magical fairy dust falling from the sky as well

This part is correct the motor is 60Hz 30 Hp at 72 amps, you don't get more Hp when you increase the Hz, you will get a decrease in Torque, and a increase in RPM only, no type of magic can turn a 30 Hp motor into a 60 Hp motor

[HillBilly]

all I can say is I understand because I didn't get it at first either. maybe because you're stuck on this 60 Hertz base setting.

[HillBilly]

(121.3 Hz Max ) at 72 amps

here's a clue. Compare this to the 60 Hertz data. there's only one way you can get 120Hz at 72 amps.