VFD / Motor experts, O.L. Faults on Yaskawa V1000

Gene Bond said:

Yes, the torque available at 1800 rpm (90hz) would be right back where you were with the 1800rpm motor (@60hz). Still just 5hp.

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I'm not sure of this but motor impedance/resistance will ask for more voltage at 90hz but you will be topped at max voltage when reaching 60hz so current will decrease and Torque will decrease too untill you reach the point where conveyor ask too much torque to run. You need a safety factor to do that and here is doesn't seem to have much room...with a 5hp....

the gearbox handle the nominal torque of a 5hp 1800rpm so theoretically the gear box won't suffer of using a 7.5hp as long as you aren't asking for more torque at 60hz...the 7.5 will just have more remaining torque a 15hz but probably still less than the 5hp at 1800rpm.


With the yaskawa, can you boost the output voltage a little bit at low rpm? You could get more power with the same current....Not sure how far you can go this way but i use to do this when i have to move a sticking belt...

milmat1 said:

which gets back to my original statement, which I was hoping to verify. We simply haven't got enough HP to begin with.
Yes we could change the gearbox and get the motor in a happier spot on the RPM scale, but at the cost of reducing the top speed.
The big man upstairs (The Owner) Want to put a vector drive Baldor on this thing. Because it claims 100% Torque down to 0Hz.
I cannot understand how it does this though, Without using more current......

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It can't - you will still need the same current. However, the unit is probably rated for constant torque and the electronics can handle the high current at low speed.

The first step is still to determine how much torque you need. A 5 hp motor of any brand won't deliver more than rated torque. Work with the supplier to make sure you have the needed torque at the low speed.

another option to install proportional control valve

If you can run successfully at full speed, you are not short of HP. Just as Tom Jenkins mentions, you are, instead, short of torque possibly at the lower speeds or probably just short of cooling capacity in the shaft-fan cooled motor.

If you can inexpensively change the power train ratio, as in belts/pulleys or chain/sprockets, resize the pulleys or sprockets so the motor is at 90hz at the load machine's top speed. No, you will not loose torque at the top end because the reduced torque in the motor is exactly offset by the increased mechanical reduction ratio.

By making this change, you reduce the low speed motor torque by one-third and increase the motor's low speed cooling by 50%. What is really happening is that you now have 5hp from full speed (90hz) down to 2/3 speed (60hz) and proportionally less hp from 60hz down to your lowest speed (which is now 50% faster than before).

This is not smoke and mirrors. Look in any commodity motor handbook and you will see that there is constant hp available from 60hz to 90hz. Upping the mechanical ratio simply uses all 5hp over a larger portion of the load's speed range. Without the ratio change, the only place you have 5hp is at full speed (60hz). The hp goes down proportionally as speed goes below 60hz.

The suggestion of changing to a 6 pole 1200rpm motor would accomplish the same thing if there is room for the larger motor and the mechanical ratio is too hard or expensive to change.