Changing Voltage and Frequency Question

[mstephenson]

The question I have is, will electrical equipment (motors, drives, solenoids, plc power supplies) listed at 400 volts/50 hertz work properly at 480 volt/60 hertz? Now let me give some background on what I have and maybe someone could advise me on potential problem that I may run into. This is used equipment that was originally built for and installed in Australia and was run for 3-4 years at 400 volts and 50 hertz. The equipment has been relocated here in the states and I have the opportunity to rewire it. This is the first time I have run across this and just had a few concerns with the differences in the voltage and frequency, they also brought the cabling that was used in the original installation, which is not UL listed and have asked if we can reuse the old wiring. My concerns on the wiring are, would there not be a difference in the amperage with the changed voltage and frequency? Also, does the wire have to be UL listed to be used in the US? There are over 100 motors, some powered by drives, some on starters (will there be a problem with coils pulling in?), about as many solenoids and photo eyes, I know the limit switches should be ok to reuse. Any help would be greatly appreciated.

 

[Phase]

When it comes to an inductor "coil of wire" it has a certain amount of resistance, inductance and inductive reactance. When an AC voltage is applied to this inductor "coil" and a circuit is completed current still start to flow, once the first positive half cycle starts to climb to its most positive amplitude "peak" it starts to "cut" into the adjacent coils, this "cutting" action induces a magnetic field into the coils of the inductor. Once the AC wave form starts to fall and is headed toward its negative half cycle it must pass through the point of zero potential, at this point in time the built up magnetic field "due to the cutting action" collapses and induces a voltage of its own back into the inductor. This induced voltage known as "inductive reactance" and is 180 degrees out of phase with the applied voltage, and will try and limit "push back on" the amount of current in this circuit. Again the AC wave form will continue into its most negative direction and will hit its "peak", and start heading back to the positive direction. Once it reaches its point of zero potential the voltage will be zero and the magnetic field will collapse and inductive a voltage back into the inductor.

There is a number of different ways to determine the amount of inductive reactance, - 2*pie*F*L. F-frequency, L-inductance (measured in Henry's). The inductance of an inductor can be calculated like this - inductive reactance / 2*pie*F.

So you can see "via calculations" the higher the inductance of an inductor, and the higher the frequency the more induced voltage (inductive reactance) an inductor will induce. So if we had an inductor with a lower amount of inductance we would need to apply a higher frequency to produce the same amount of inductive reactance opposed to inductor with a higher inductance.

So if you have a inductor that says it should be operated on 400VAC 30hz and 60hz is applied to that specific inductor it will induce a Higher amount of inductive reactance into the circuit, therefor limiting more current then originally intended to operate on.

Please keep in mind that I was talking specifically about the resistance being negligible, inductors to exhibit internal resistance, therefor the total limiting factor would be the %Z. This can be computed using vector addition since the resistance and inductive reactance are usually out of phase.

I tried to keep this as simple as possible without to many calculations, so I'm sorry if this is not understandable.


Scott.

 

[Besoeker]

The question I have is, will electrical equipment (motors, drives, solenoids, plc power supplies) listed at 400 volts/50 hertz work properly at 480 volt/60 hertz? Now let me give some background on what I have and maybe someone could advise me on potential problem that I may run into. This is used equipment that was originally built for and installed in Australia and was run for 3-4 years at 400 volts and 50 hertz. The equipment has been relocated here in the states and I have the opportunity to rewire it. This is the first time I have run across this and just had a few concerns with the differences in the voltage and frequency, they also brought the cabling that was used in the original installation, which is not UL listed and have asked if we can reuse the old wiring. My concerns on the wiring are, would there not be a difference in the amperage with the changed voltage and frequency? Also, does the wire have to be UL listed to be used in the US? There are over 100 motors, some powered by drives, some on starters (will there be a problem with coils pulling in?), about as many solenoids and photo eyes, I know the limit switches should be ok to reuse. Any help would be greatly appreciated.

Fixed speed motors, those with starters, will run 20% faster on 60Hz. That may well be a problem. Even a headache.
Those on variable speed drives may be OK provided the VSD is rated to operate at 480V input. Many are specified to operate over a range of input voltages. The frequency ought not to be an issue
Solenoids will probably be OK - the V/f ration is the same for both systems.
PLC power supplies - again check the spec. on input voltage.

Wiring,I don't know.......