Drive Swap Advice

Tim Ganz · Aug 19, 2014

I have a machine that has a failed Yaskawa drive. The drive on the machine is a F7 model and is a 17 amp drive and I have a spare A1000 model that is a 31 amp drive.

This is on a center winder application and I wanted to see if I can use the 31 amp drive as it's a brand new spare that went to a machine we scrapped earlier in the year. If has encode feedback with the encoder built into the Baldor motor but since the encoder is so hard to change when it fails we do run it in encoder less mode until we have a scheduled shutdown.

I set it up on the bench and it appears to take the 10 HP drive and amp setting ok but I am not sure how it will control and this being a winder we need decent control.

Any tips?

Tim Ganz · Aug 20, 2014

jraef · Aug 20, 2014

Should be fine. Most VFDs can accept a motor size at least 50% of the unit rating, some even slightly less. The only real issues are that the current sensors can start to lose accuracy at very low loads on motors that are too small, which can affect SVC algorithms (but is often fine with V/Hz mode), and it sounds as though you will be using SVC. Secondly, VFDs are required to provide the motor short circuit protection now, because the motor is no longer directly connected to the up stream branch circuit protection. So when the motor is too small, that SCPD function may be out of range for that motor if it can't adjust itself low enough (usually associated with the first issue).

But 17A of a 31A drive is probably fine. Typically the drive mfr will give you a warning if you attempt setting it out of range, or simply not allow the settings to go low enough. So if it allowed it, that's likely an indicator that it's OK.

But RTFM...

Tim Ganz · Aug 24, 2014

jraef said:
Should be fine. Most VFDs can accept a motor size at least 50% of the unit rating, some even slightly less. The only real issues are that the current sensors can start to lose accuracy at very low loads on motors that are too small, which can affect SVC algorithms (but is often fine with V/Hz mode), and it sounds as though you will be using SVC. Secondly, VFDs are required to provide the motor short circuit protection now, because the motor is no longer directly connected to the up stream branch circuit protection. So when the motor is too small, that SCPD function may be out of range for that motor if it can't adjust itself low enough (usually associated with the first issue).

But 17A of a 31A drive is probably fine. Typically the drive mfr will give you a warning if you attempt setting it out of range, or simply not allow the settings to go low enough. So if it allowed it, that's likely an indicator that it's OK.

But RTFM...

This worked fine. Thanks for the advice above. Unfortunately this was a topic not covered in the manual though.

Drive Swap Advice

Tim Ganz

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Tim Ganz

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jraef

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Tim Ganz

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