# Huanyang vfd puts out 175v instead of 220v



## Sblack (Dec 20, 2019)

as the title suggests this vfd runs fine but puts out only about 75% of the proper voltage. To make things interesting he included manual is only in Chinese! Why do they even bother? There is a table of parameters and it shows units and default values and from that I managed to change the frequency to 60 from 50 and speed up the acceleration. So the thing does work. But I can’t imagine why it would put out such an odd voltage.
it is a zw g2 2t 3, whatever that means. It says on the case that it outputs 220v at 3 kw. Any idea what parameter could be changed? Any idea where I might find a manual?  

Right now it is just hooked to a 600v 3phase doall vertical bandsaw but given that it shows 400v at the transformer output and 175v at the transformer input I don’t want to try turning on the saw. could the vfd be interacting with the transformer in a way that I don’t understand? I understand just the basics of electricity. Start talking about power factors and back emf and my eyes glaze over.

any advice appreciated


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## MikeInOr (Dec 20, 2019)

I think you might need a True RMS (root mean square) volt meter to accurately measure the voltage coming out of a VFD since the wave form is probably not a perfect sine wave.

https://www.fluke.com/en-us/learn/blog/electrical/what-is-true-rms


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## mksj (Dec 20, 2019)

You cannot measure the VFD output voltage with a conventional multimeter/RMS, the wave is a function of many smaller voltage on/off pulses that occur well beyond the capacity/frequency of typical sinusoidal AC wave. You need a scope to measure the output. You can set the display on some VFDs to show all the different operating and performance characteristics of a VFD, not so on the cheaper Chinese ones, let alone programming limitations. There are tons of HY manuals on the net. "HY VFD manual"








						How to Measure Output Voltage from a VFD to a Motor
					

How to measure output voltage from a VFD to a motor




					www.fluke.com
				




You cannot use the VFD output to drive a power transformer if that is what you are doing. So maybe add some clarity as to how you have it hooked up, specifications of what your driving, and what are the issues or problems your are having.


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## ub27Rocks (Dec 20, 2019)

The most obvious response might be to go back to the vendor to get the English version of the manual? Can't answer the other questions, although driving a transformer seems unlikely.


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## Sblack (Dec 20, 2019)

So a fluke set to


mksj said:


> You cannot measure the VFD output voltage with a conventional multimeter/RMS, the wave is a function of many smaller voltage on/off pulses that occur well beyond the capacity/frequency of typical sinusoidal AC wave. You need a scope to measure the output. You can set the display on some VFDs to show all the different operating and performance characteristics of a VFD, not so on the cheaper Chinese ones, let alone programming limitations. There are tons of HY manuals on the net. "HY VFD manual"
> 
> 
> 
> ...



ok thatwould explain the blinding flash!  I ”was” running a 220v vfd to generate 3phase power and ran that into a 3phase transformer to step up to 600v. So I guess the transformer messes with the vfd somehow? Can you explain? Anyway, after readingup a bit and learning that the meter was probably reading incorrectly and everything else seemed to be working I tried to turn on the saw. That’s when the flash happened. Ittripped the 25amp breaker and fried the vfd and made a loud pow.

so I guess I need to use a rotary converter?


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## JimDawson (Dec 20, 2019)

I think a rotary converter would be the correct answer.


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## Joe in Oz (Dec 20, 2019)

WHY would a transformer not work????
The arrangement of coils in a transformer are VERY similar to those in a motor - for which a VFD is designed - except that no torque vector is generated. The fact that the output wave form isn't quite sinusoidal would have EXACTLY the same effect on a transformer as it has on a motor.....
I would be interested for you to find the root cause of the "flash".
You didn't by chance have the VFD already running when you switched on the bandsaw, did you???? You must NEVER switch a load downstream of a VFD - either on or off (adding or subtracting a small load like a coolant pump has been successful for lots of people).


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## Sblack (Dec 20, 2019)

Joe in Oz said:


> WHY would a transformer not work????
> The arrangement of coils in a transformer are VERY similar to those in a motor - for which a VFD is designed - except that no torque vector is generated. The fact that the output wave form isn't quite sinusoidal would have EXACTLY the same effect on a transformer as it has on a motor.....
> I would be interested for you to find the root cause of the "flash".
> You didn't by chance have the VFD already running when you switched on the bandsaw, did you???? You must NEVER switch a load downstream of a VFD - either on or off (adding or subtracting a small load like a coolant pump has been successful for lots of people).



i had to have the vfd running as it powers the motor contactor on the band saw


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## Flyinfool (Dec 20, 2019)

VFDs and transformers on the output do not play well together. You would be better off getting a 1P 220 to 440V transformer and then using a 440 1P to 440 3P VFD to drive the motor. This way you will still be using all of the features of the VFD. (assuming the motor can handle it).
Depending on just what transformer you have, certain 3P transformers can be hooked up to 1p power so there is a slight chance that the transformer you have can be used on the input side but it will be very de rated.

Another option is to use a rotary phase converter to convert the 220 1p into 220 3P and then feed that into your transformer. Not ideal but better than the VFD.

CAUTION: Semi technical stuff sort of translated into layman's terms to follow........... Read at your own risk......
Not all motors will last long on a VFD, That is why they now make most modern motors with a "Inverter Duty" rating. Technically a VFD is outputting DC. The way it works is by pulsing the DC power on and off very fast. When it is simulating the peak of the wave form the DC power is on for a longer time, as the simulated sine wave gets closer to the zero volt part of the cycle the DC power is on for a very short time. So the average of all that kind of follows the intended sine wave. But  any time it is in the on part of the cycle it is outputting 312V DC.The motor insulation on the winding has to be able to handle this voltage without breaking down over time. The output of the 440 VFD will be pulsing 624V DC pulses into your 440 motor. If it is a very old motor it may not like this if you run heavy loads and make the motor work hard.

As for why the transformer will not work, I have never seen a transformer rated for inverter duty, A transformer works by having a nice clean pure sine wave power coming into it. A VFD is about as unclean of a power source as you can get, this unclean power will cause the transformer to get very hot due to the eddy currents that will be happening with all of the DC voltage spikes. I motor does not care if the input power is clean or not. They both use the some kind of power but they use it in very different ways.


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## JimDawson (Dec 20, 2019)

Joe in Oz said:


> WHY would a transformer not work????



The VFD output waveform instantly saturates the the transformers iron core and the current spikes.


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## mksj (Dec 20, 2019)

Transformers are design for specific operating frequency, more or less less sine waves, the sharp on/off pulse of a VFD is more like hitting a brick wall and the primary current goes vertical as Jim mentioned. VFD is probably toasted. Electronics, switch gear, contactors/coils, capacitors... also do not play nice being fed with the output of a VFD.  There are types of transformers used on the output of VFDs which are specifically for that application and operated at a fixed frequency. There is mention of this for larger motors for wells,  offshore submersible applications, etc. where the higher voltage = smaller cables/wires. Very expensive. I am a doctor not an engineer, so I just know what I read and have been installing/working with VFDs for the past 10 years.

What is typically done  is to use a step-up transformer before the VFD, and then use the VFD to drive the 3 phase motor. The additional problems you would encounter, would be if feeding this with single phase then the VFD size would need to be ~doubled (5 Hp) to operate in a derated mode and it may not operate at all because of phase loss. Additional problem is the VFD voltage spikes on an older motor cause much more rapid degradation of the insulation and motor bearings (i.e., don't do it on an old 600V motor). Easiest approach is a 230V RPC to your current step-up transformer for 600V 3 phase to the machine. If you want VFD speed control, replace the motor with a 230VAC 3 phase motor.


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## Sblack (Dec 20, 2019)

The saw has an infinitetly variable vbelt drive so no need for the variable speed feature. I think I will go with a rpc. Thanks for the education.  I am $130 poorer but better informed than I was this morning. Live and learn.


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## markba633csi (Dec 21, 2019)

The failure was most likely because you connected the load while the VFD was running.  But even so, it would have been an inefficient setup.  
An expensive lesson for sure
M


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## Sblack (Dec 21, 2019)

So should I have bypassed the contactor on the saw and run it direct from the vfd? In that contactor there are phases split out for the blade welder, coolant pump and hydraulic pump So that would have required rewiring it all. But perhaps those were single phase. Anyway, I am more peeved at the waste of precious spare time than the 100 bucks And I learned something. Better I smoke this than something high dollar. 

thank you to everyone here who shared their knowledge. Note to self: in the future ask here BEFORE you go out and buy stuff.


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## Superburban (Dec 21, 2019)

If you study how the saw works, it is likely simpler to use the switch that controls the contactor, to directly control a VFD, bypassing the contactor. You want the VFD to be wired directly to the motor it is controlling. I found, if you have 3 3 phase motors, I would run 3 VFD's. Except for lights, switches do not care how much voltage is going through them.


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## Joe in Oz (Dec 22, 2019)

To sblack: ABSOLUTELY! 
You should NEVER have contactors downstream of a VFD.
The main motor HAS to be connected directly to the VFD. Secondary smaller motors can be switched on and off AFTER the main load is running.
A blade welder will NOT run off a VFD, by the way.


Cheers
Joe


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## Joe in Oz (Dec 22, 2019)

JimDawson said:


> The VFD output waveform instantly saturates the the transformers iron core and the current spikes.


Hi Jim. 
Have you looked at the wave form of a VFD with a motor connected and running (with a scope)? Or for that matter with a transformer and motor connected and running?
Let me tell you you would be surprised....

Why do you think it would "instantly" saturate an iron core on a transformer and not on a motor? It certainly isn't a square wave or a saw-tooth wave form.
So I still don't understand why theoretically you can't use a transformer.

Someone else said a transformer is designed for a specific frequency. Yes, true. That only means it will be less efficient at another frequency. 
50Hz transformers work OK on 60Hz - a 20% mismatch. So would a 60Hz transformer be OK at 72Hz? Maybe even at 100Hz?
I don't run any of my motors faster than 100Hz, because of bearings and ventilator fans.... and rarely slower than 20Hz because of lack of cooling (I mean of course under significant load).
So I don't buy that argument for this scenario, sorry. 

In any case, I admit that I have 'ignorantly' connected a 3-phase transformer between a VFD and a motor and it worked fine. The transformer happened to be double the rating of the VFD and the motor was about half the rating of the VFD.
When I needed a bigger motor on that machine, I used a single phase transformer and a bigger 415V VFD, so I haven't got the old installation running any more.

Cheers
Joe


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