60 Hz VFD on 50 Hz Service

I concur with previous comments but wish to add a cautionary note.

I have encountered a situation where motor/pump combination was run in the +/- 10% voltage range and all seemed good UNTIL motors started burning out. (The VFD was being used to vary the motor speed and on occasion was running at faster than design frequency)

The overload protection became ineffective, since overload current at "normal" was not exceeded at the higher supply voltage, all seemed well. Further investigation determined that running continuous duty for extended periods at that condition led to excessive heating in the coils/iron and eventual motor failure.

If you operate at a different frequency, check that the new operating conditions have appropriate modification of the protection circuits.

Just an Eng makes a good point.... Filters can be used to limit voltage, but there is no substitute for good engineering...

"There are basically three different types of commercially available filter networks for reducing the overvoltages at the motor terminals. These filters are typically installed at the output of the VFD. Line reactors (inductors), resistor-capacitor (R-C) snubbers, and R-L-C low-pass filters are commonly used to reduce the voltage at the motor terminals. In the majority of cases, the R-L-C low-pass filter has been found to be the most effective filter. However, the user should consult the VFD vendor to select the filter that will match the specific VFD that is selected for the application."

"Use of 230 V / 460 V Motors

Many motors are designed for operation from either a 230 V or a 460 V supply. In such cases, 230 V VFDs and motors rated 230 V / 460 V will solve the problem. This is because the insulation systems for dual-wound motors are designed for 600 V rms operation; when 230 V is used, then even if voltage magnification occurs at the motor terminals, the peak voltage is still below the insulation withstand capability of the motor. This is a viable option for many small fractional horsepower motors that have the provision for either 460 V or 230 V operation."

http://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/vfd_motors.pdf

As stated a VFD does not care about the incoming Hz, as for running your pump with the same performance.

Pump performance depends on efficiency and Hz or RPM, to find out what that is you need to study the pump curve and then what the rate of flow is at your new Hz. To work out what your flow rate would be you need to apply the "laws of affinity". (Google it).

you have two options regarding the voltage.

1. run your motor at the output voltage of your drive, that might decrease the motor HP, (you've not mentioned the drive output voltage or motor NPV) and means you MAY not be able to use a pump with the same number of stages.

2. get yourself a step-up transformer

find the formulas regarding voltage/Hz change & the "Laws of affinity". they should help you.

Will there be no problem with the DC voltage ripple on the DC bus in the VFD.

It takes more time in a 50Hz system to reload the DC bus capacitor. The result is that the mean voltage level of the DC bus will be lower. This can cause to under voltage trip on the VFD.

THANK YOU ALL FOR THE FEEDBACK. THE vfd MANUFACTURER CONCURS. i LIKE THE REMINDER ABOUT LINE REACTORS; THEY SEEM LIKE A GOOD IDEA ANYWHERE. aS TO THE PUMP PERFORMANCE, MY RELATIONSHIP TO THE AFFINITY LAWS GOES BACK TO THE SLIDE RULE I STILL KEEP IN MY DESK. THE ONE THING I'M SURE OF IS HOW TO SET THE PUMP UP. SOFTWARE MAKES IT A BIT EASIER THESE DAYS.

JT

good to hear that the slide rule is not dead..