50Hz Equipment

[blues]

I have a client who would like for us to provide an electrical feed to some motorized equipment that operates at 50Hz. I will need to transform down the voltage to meet their requirements. My questions is what are the adverse effects if I supply the equipment at 60Hz? What are my options? My supply will terminate into a motor control cabinet that has associated control wiring.

Thanks in advance for any advice.

Dan Craven

 

[LarryFine]

Anything frequency-dependent, such as most AC motors, will run at 6/5 normal speed.

 

[PetrosA]

Also, some servo controlled stuff may lose accuracy. A simple example would be an automatic 3 bay doser in a a washing machine that will not send the water sprayer to the correct bay for pre-wash, wash and rinse.

 

[Brian Oshman]

Running 50 Hz equipment on 60 Hz will burn it up.

 

[LarryFine]

Running 50 Hz equipment on 60 Hz will burn it up.

Not necessarily. There are many devices with 50/60Hz ratings, such as contactor coils. They'll say something like "120v 60Hz/110v 50Hz."

Equipment not so marked can still be operated on the others' frequency, as long as the limitations are observed. Others here can add more.


Others?

 

[Brian Oshman]

Not necessarily. There are many devices with 50/60Hz ratings, such as contactor coils. They'll say something like "120v 60Hz/110v 50Hz."

Equipment not so marked can still be operated on the others' frequency, as long as the limitations are observed. Others here can add more.


Others?

That is right, equipment with 50/60Hz rating burt not 50 Hz.

You can run 60 Hz equipment on 50 Hz but not the other way around. Overclocked equipment will and does burn up.

 

[LarryFine]

That is right, equipment with 50/60Hz rating burt not 50 Hz.

You can run 60 Hz equipment on 50 Hz but not the other way around. Overclocked equipment will and does burn up.

Thank you, Others.

 

[Jraef]

Anything that converts AC to DC, i.e. power supplies, drives, ballasts not likely a problem. Anything with coils, potentially a problem. Motors; 20% over speed and more HP, so possibly some mechanical problems. Also, motors work by virtue of having their designed V/Hz ratio supplied. So if the motors are designed for 400V 50Hz. that is a V/Hz ratio of 8:1. If you supply 60Hz, you must also supply 8 x 60 or 480V. So in that case, do NOT tansform down to the nameplate voltage; leave it alone (assuming the speed is not an issue).

 

[Brian Oshman]

^^^Actually all components operated on 60 Hz that are designed to run on only 50 Hz will burn up.

60 Hz components operated on 50 Hz are not a problem even if not listed as such because they are not overdriven.

I work with a lot of foriegn equipment and any unit that was put into service that was not built specifically for North American use would self destruct over time.

This included motors, ballasts, transformers, capacitors, etc... Transformers used in power supplies rated at 50 Hz would also fail. The power supply after the transformer would be OK due to the regulators and it being DC at that point but the step down transformers would go bad.

If this machine is going to be used occasionally or intermittently then it will probably last for years but if it is going to be subject to constant use then it will self destruct over time.

You can try a VFD or frequency converter on it to reduce the clock speed but as mentioned before you may run into calibration issues due to the winding ratio differences.

It may be easier and more reliable to find replacement components to install in it otherwise just hook it up and count your blessings for every day you get out of it.

 

[blues]

50Hz Equipment

I appreciate all of the advice. This is very expensive equipment I was hoping for a more permanent solution. The equipment will be used intermittenly.

Dan

 

[gar]

090619-0919 EST

Brian:

The statements you are making are wrong and should not be propagated as fact.

Provide a technical analysis for the statements you are making, and provide some definition of the devices you are referring to.

60 Hz components operated on 50 Hz are not a problem even if not listed as such because they are not overdriven.

As a general statement this is nonsense and wrong.

If you ever studied the theory of ferromagnetic circuits, then you would know that the magnetizing current goes up very rapidly as you lower frequency with constant applied voltage because the core is driven further into saturation. This is simply a result of the volt-time integral.

.

 

[Brian Oshman]

090619-0919 EST

Brian:

The statements you are making are wrong and should not be propagated as fact.

Provide a technical analysis for the statements you are making, and provide some definition of the devices you are referring to.

60 Hz components operated on 50 Hz are not a problem even if not listed as such because they are not overdriven.

As a general statement this is nonsense and wrong.

If you ever studied the theory of ferromagnetic circuits, then you would know that the magnetizing current goes up very rapidly as you lower frequency with constant applied voltage because the core is driven further into saturation. This is simply a result of the volt-time integral.

.

I agree with you on that particular statement about running 60 Hz on 50 Hz and stand corrected however, I stand by the rest of my statements that you cannot operate 50 Hz equipment on 60 Hz without adverse effects and that is based on years of correcting problems with prototype equipment imported with 50 Hz components that fail. It is real world experience. I have no reason to make it up.

Motors, transformers, and ballasts, and other types of components of this nature are designed for one frequency and will self destruct on another frequency. Components that are dual frequency generally will have two separate windings calibrated for each frequency.

For the original poster, you will probably not have any trouble doing so as you mentioned that it will be only light duty intermittent use but if it is expensive equipment then look into a frequency converter to reduce or eliminate risk of permanent damage.

 

[LarryFine]

If you ever studied the theory of ferromagnetic circuits, then you would know that the magnetizing current goes up very rapidly as you lower frequency with constant applied voltage because the core is driven further into saturation. This is simply a result of the volt-time integral.

What if you lower the applied voltage proportionately?

 

[Besoeker]

Not necessarily. There are many devices with 50/60Hz ratings, such as contactor coils. They'll say something like "120v 60Hz/110v 50Hz."

Equipment not so marked can still be operated on the others' frequency, as long as the limitations are observed. Others here can add more.
Others?

As ever, you are the voice of reason.
And I am others...:wink:
Excluding some specialist applications, the world has 50 and 60Hz at the point of use.
Much domestic and consumer electronic kit is designed to accommodate all world standards. The chargers for my lap top and phone are both 100-240V and that seems to be common for "wall warts". That's useful if you have to travel to different countries.

 

[ibew501ed]

Wouldn't it be possible to use a VFD with a 60hz input with a 50hz output before a transformer that would then bring 480 down to 380 (or what ever is required) or would that be cost prohibitive?

 

[templdl]

Gentlemen,

Regarding induction motors and transformers, A motor or transformer designed fo 60hz will with almost all certainty overheat and fail when applied a 50hz.
The core of a transformer will saturate causing the primary current to sky rocket and the secondary voltage to collapse. In other words the transformer will sense being a transformer.
Both transformers and motors are designed with more core steel to deal with the greater flux density created by the lower frequency. 50hz transformer cost more in material to make.
A motor or transformer designed for 50hz will work fine when applied at 60hz. The motor speed however is based upon its synchronous speed at the frequency it is powered by.
A 4p motor will have a synchronous speed of 1200rpm ay 50hz and 1800rpm at 60hz.

Other that the nameplate showing only 50hz they can be applied a 60hz. However, in so much as the NEC in concerned it would be a misapplication as the device isn't be applied per the nameplate per Art 110. Most transformers an motors can be labeled 50/60hz if they have beem designed for 50hz anyway. As such it may make sense to specify 50/60hz.

 

[gar]

090620-1324 EST

Larry:

You are correct that if you lower the voltage in proportion to lowering the frequency for the same transformer, then the same saturation level is reached.

The integration of voltage over time scaled by some constant determines the flux density. What is integration? It is the summation of very small areas from one limit to another. The very small areas in this case are the magnitude of the voltage times an infinitely small increment of time. What the integration does is calculate the area under the voltage curve from one point in time to another.

So consider a sine wave. Let zero degrees be the positive zero crossing. The integral from 0 deg to 0 deg is 0 because there was zero area under the voltage curve from 0 to 0. Note as we move from 0 deg to 180 deg the value of the area under the curve increases. The integral of sin u du is -cos u. When you evaluate the integral from one point to another the final value is evaluated first and the initial value second and subtracted from said first.

The integral from 0 deg (0 radians) to 90 deg (Pi/2 radians) is - cos 90 - (-cos 0) = -0 - (-1) = 1 . Next consider the integral over the full half cycle. The result is - cos 180 - (- cos 0) = - (-1) - (-1) = 2 .

If we want to know the average value of a half wave rectified voltage, then we divide the area under the curve by the base of the curve over which the average is being determined. For this calculation the angle is measured in radians. The base for a full cycle is 2*Pi. Thus, the average is 2/2*Pi = 1/Pi = 0.318 . If we want the full wave rectified average value, then double this value and the result is 0.636 . This you might recognize as the constant to convert the peak value of a sine wave to its full wave average value.

In a similar fashion you can derive the constant for conversion of sine wave peak to its RMS value. The integral of sine squared is (u/2) - (sin 2u/4). RMS is the root mean square. For 1/2 cycle this is (Pi/2 - 0) - ( 0 - 0 ) = Pi/2 . To average this divide by the time of 1/2 cycle, (Pi/2)/Pi = 1/2 . Then take the square root (the root part of RMS) and the result is 0.707 . Again a familiar constant.

Back to the magnetic circuit. As you progress from the positive zero crossing of the voltage to the negative zero crossing the flux is increasing according to the function K * ( 1 - cos u ). Therefore maximum flux density in the positive direction occurs at the negative zero crossing. Look at photo P7 on my web site at
www.beta-a2.com/EE-photos.html
Here you see the maximum magnetizing current pulses occurring at the negative zero crossing, about 0.9 CM on the scope scale for the first peak. These pulses result from the core going into saturation.

In the magnetic circuit the flux is a result of the time the voltage is applied and thus a scaling factor has to be applied in front of the integral that is proportional to the period of the sine wave. Period is the inverse of frequency.

The integral alone of the sin gives us the shape of the buildup of the flux. The absolute magnitude of the flux and therefore flux density is determined by the length of time for one cycle and other parameters, such as, number of turns, core material, and cross-sectional area of the core.

.

 

[Speedskater]

Gentlemen,

(snip)
A motor or transformer designed for 50hz will work fine when applied at 60hz. The motor speed however is based upon its synchronous speed at the frequency it is powered by.
A 4p motor will have a synchronous speed of 1200rpm at 50hz and 1800rpm at 60hz.
(snip)

I completely agree with the rest of your post.
But won't the 60hz RPM be 1440?

 

[gar]

090620-1956 EST

Comments on post #16 by temldl.

The synchronous speed of a 2 pole motor is 3600 RPM for 60 Hz, 60 revolutions per second. A 4 pole is 1/2 this RPM or 1800.

For 50 Hz it is 50 rev/sec and thus 3000 RPM. For the 4 pole it is 1500 RPM.


A 3 phase induction or synchronous motor designed for 50 Hz will work quite well at 6/5 higher RPM and 6/5 higher voltage, but may be inappropriate for the load. It is not uncommon to take a standard induction motor (1800 RPM nominal) and drive it with a vector drive at maybe 120 Hz (3600 RPM nominal). Not the best idea but it works. It is better to use a motor designed for vector service. We did this with a standard 5 HP unit on a machine that builds automotive differentials. The various speeds were 3000, 1800, 900, and 600 nominal RPM from a 4 pole motor. In a second machine modified in the same way we changed the motor to one designed for vector service. Prior to using the variable speed excitation a two speed motor was used. With the vector drive we had four speeds available and the speeds were adjustable.

A single phase capacitor run and/or start motor designed for 50 Hz may work OK at 60 Hz in some applications, but not others, and probably not at full load. Probably OK on a drill press.

A home refrigeration unit designed for 50 Hz should not be run at 60 Hz. Here you have an optimized package of compressor and motor designed for minimum cost and almost certainly there will be a problem from speed relative to the compressor and overheating from the marginal design. What the nominal voltage is becomes another factor.

.

 

[gar]

090620-2034 EST

brian:

On your post #12.

I agree that there are many devices rated for a particular frequency that should not be operated very far off frequency. Sola ferro-resonant constant voltage transformers are one in particular.

But there are many other devices that can operate very well over a substantial frequency range. One needs to understand how the device and/or its load works and make judgements from this knowledge to determine whether one can operate at non-normal conditions.

As an example there are 3 phase CNC machines that be be operated from single phase with or without modification of some of the components. The main spindle drive and servos may all operate from an internal DC bus. This DC bus is created directly from rectifiers off of the line into a capacitor input filter. This no transformer is needed. By increasing the filter capacitance and the peak current capability of the rectifiers this can be supplied from single phase. If auxiliary motors are all single phase then the modification is simple.

.