400V 50HZ operate on 480V 60 HZ

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winnie said:
@Deltaforce :
Motors overload based on _current_ not power.

With the increased voltage available this motor will operate at correct V/Hz and be able to produce full torque at the higher speed without overloading.
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HP=Torque×speed

Full load HP=Full load Torque×Rated speed

HP=Full load Torque×Higher than Rated speed

mean

HP more than full load HP

mean

more than motor rated current

50hz motor take

mean

motor overload
 
Mechanical output power is torque * speed

Higher speed at full torque means greater than rated power.

On this we agree

Electrical input power is voltage * current

Higher input voltage means lower input current for the same power

Overloads response to input current, not input power

If motor is operating with proper V/Hz then higher speed results in higher power without overload real or sensed
 
Same torque, frequency changes from 50Hz to 60Hz.

Output power goes up by 6/5.

Input voltage is also changed from 400V to 480V. Input voltage goes up by 6/5.

What happens to input current?
 
winnie said:
Same torque, frequency changes from 50Hz to 60Hz.

Output power goes up by 6/5.
Click to expand...
More issue than that

OP fan load

6/5 speed rise

HP require up by 6/5x6/5x6/5

Per fan law

Motor voltage increase by 6/5

Motor current need by 6/5x6/5
 
Deltaforce said:
Any refer kindly
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You already know this. You know how motors operate on VFDs. Below base speed the motor and drive is in the 'constant torque regime'. The VFD has sufficient voltage capability to maintain proper V/Hz ratio, so that the design magnetic flux density is maintained, and the motor operates at design torque per amp. Since the current is limited by motor heating and VFD current rating, if you maintain design V/Hz ratio the torque is limited to a roughly constant value. (Note: I;m ignoring things like short term overload capacity of the inverter or thermal overload capacity of the motor. The point is that at proper V/Hz ratio at a given fixed current value you have an approximate fixed torque value even as frequency and speed changes.)

The key in the above is VFD operation below base speed, which you already know about. You described it thusly:
https://forums.mikeholt.com/threads/400v-50hz-operate-on-480v-60-hz.2572875/post-2818035
A vfd operate 50Hz motor 400 v constant HP mode base speed above

Torque reduce

Overload not it
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But the question is: 'What defines base speed?' Hint: it isn't the number printed on the motor nameplate.

'Base speed' is set by the frequency at which the inverter is capable of supplying sufficient voltage to maintain proper V/Hz ratio. Commonly this happens to be the number on the nameplate because the inverter is connected to the same line voltage that the motor is designed for. But if you do something to enable the inverter to operate at a different voltage, then the 'base speed' will be different.

A common trick is to take a NEMA dual voltage motor, wire it in the 230V configuration, and then use it with a 460V VFD. In this case the 'base frequency' becomes about 120 Hz, and such a motor probably cannot be used all the way up to its new 'base speed' because of mechanical limits. On the other side of the coin, a 460V motor can be connected to a 230V VFD if you make the 'base frequency' 30Hz.

In the present case, a 400V 50Hz motor used on a VFD connected to a 480V supply would have a new 60Hz 'base frequency'.

Jon
 
Deltaforce said:
More issue than that

OP fan load

6/5 speed rise

HP require up by 6/5x6/5x6/5

Per fan law

Motor voltage increase by 6/5

Motor current need by 6/5x6/5
Click to expand...

As stated above: if the _fan_ used is the one originally designed for the 50Hz motor, then I agree with you. The OP has a system with a 1800 RPM fan and a 60Hz motor. If they replace both the fan and the motor, and use a 50Hz motor with its corresponding 1500 RPM fan, then they will have exactly the problem you describe here. The 1500 RPM fan will be operating at 1800 RPM, using (6/5)^3 more power than intended.

If, on the other hand they connect the 1800 RPM fan to the 50Hz motor and then run at 60Hz and 1800 RPM, then they will be back right were they belong and will be fine. The 1500 RPM motor will be spinning at 1800 RPM, exactly what the fan was designed for.

-Jon
 
Let's say I'm a motor designer and I design a motor to operate at 400V and 50 Hz. And I use internal components that are just at the limits of their ratings at those parameters, in all cases.

Now I want to extend my design to also operate at 480V and 60 Hz. What internal components will need to be upsized/upgraded to handle the new conditions? Obviously conductor insulation, if there's any 400V rated insulation it will need to become 480V rated.

Lastly, given the limited options for commercially available components (e.g. insulation is usually 300V or 600V, not weird in between values, if I understand correctly), would any actual changes be required in practice? I.e. does a typical 400V/50 Hz motor operate perfectly well at 480V/60 Hz?

Cheers, Wayne
 
The insulation system presents a limit, but is usually not a problem for motors below 600V. Pretty much all the same magnet wire is used for low voltage 'mush wound' motors.

The motor bearings will be operated at higher speed and have a shorter life in terms of operating hours.

For large motors you end up bumping into the maximum rotational speed of the rotor.

In the US, NEMA design motors are often expected to be capable of operating at higher then 60 Hz; see table 30-1 on page 10 of https://www.nema.org/docs/default-s.../mg-1-part-30-watermark.pdf?sfvrsn=793de734_1

The larger the motor is the less you can push it above 60Hz. A 1 HP 2 pole motor (nominal 3600 RPM) is expected to be safely operable at 120 Hz (7200 RPM) But a 30Hp 2 pole motor is expected to safely operate up to 90Hz, and a 60Hp 2 pole machine is limited to 60Hz.

-Jon
 
winnie said:
As stated above: if the _fan_ used is the one originally designed for the 50Hz motor, then I agree with you. The OP has a system with a 1800 RPM fan and a 60Hz motor. If they replace both the fan and the motor, and use a 50Hz motor with its corresponding 1500 RPM fan, then they will have exactly the problem you describe here. The 1500 RPM fan will be operating at 1800 RPM, using (6/5)^3 more power than intended.

If, on the other hand they connect the 1800 RPM fan to the 50Hz motor and then run at 60Hz and 1800 RPM, then they will be back right were they belong and will be fine. The 1500 RPM motor will be spinning at 1800 RPM, exactly what the fan was designed for.

-Jon
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Moderators and others forgive

My continue questions

Back to quote

1500rpm fan and 1800rpm fan

at 1800rpm

absorb same hp almost

It little difference to the motor

6/5x6/5x6/5 times rated hp require still apply.

Motor overload may
 
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