Inverter failure guidance

[GavlarParticipant @gavlar]

Looks like your motor is rated 1380 rpm at 50Hz. The motor is designed for 50hz. Pushing it to100hz will mean it runs at double it's design speed. Who knows how long it will last?

A lot of dual voltage motors are 50 or 60Hz so they can be used in the US and the UK, so pushing them to 60 or 65 hz won't do any harm, but personally I wouldn't run them much higher.

Edited By Gavlar on 08/05/2020 21:53:56

[SteviegtrParticipant @steviegtr]

There seems to be some miss conception about motor frequency. In the setting there will be a parameter for the base motor frequency to be set. That setting will give you an option of 50hz or 60hz. This needs to be set at 50hz. For UK supply. Save & exit that setting. That is that finished with. There are setting for upper & lower frequency which something different from the base setting.

Some people choose a lower of say 10hz. I have mine on the lathe at 2.5 for jogging. The mill one I have at zero. Then the upper limit is whatever you want. I have mine set at 85hz which gives the motor quite a bit more speed. Bear in mind any particular motor comes in 2 guises. A 2 pole & a 4 pole in the same frame. So your 4 pole motor will be safe to 2800 anyway. I probably would not go that high but you can. I am not familiar with the model you have bought but, most of the settings are the same. The expensive ones just have lots of parameters that are not needed for the hobby shop, just for industrial use. So whichever inverter you have.

There will be those settings mentioned. Confusing the frequency thing but that is how they work.

Steve.

Edited By Steviegtr on 08/05/2020 22:41:49

Edited By Steviegtr on 08/05/2020 22:43:13

[Rod ClemettParticipant @rodclemett60985]

Jim,

is it possible that there is a default parameter in the settings for your new inverter that needs to be reset to match the number of poles in your motor?

I'm wondering if this could be responsible for the reduced motor speed you are experiencing at 50Hz.

Clem

[Pete RimmerParticipant @peterimmer30576]

Posted by Gavlar on 08/05/2020 21:42:50:

Looks like your motor is rated 1380 rpm at 50Hz. The motor is designed for 50hz. Pushing it to100hz will mean it runs at double it's design speed. Who knows how long it will last?

A lot of dual voltage motors are 50 or 60Hz so they can be used in the US and the UK, so pushing them to 60 or 65 hz won't do any harm, but personally I wouldn't run them much higher.

Edited By Gavlar on 08/05/2020 21:53:56

Mechanically there should be no problem. Many motors come in 2-pole and 4-pole variants, the 2-pole running double the speed of a 4-pole.

[not done it yetParticipant @notdoneityet]

Speed rating maximums may depend on the type of bearings fitted. Sleeve type may not be suitable – but not sure; ball bearing should be OK – if in good condition.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Jim Young 2 on 08/05/2020 21:16:28:

…

Only one question, with a max frequency of 50Hz the lathe is slower than it was. The inverter can do 0-400 Hz. Set to a max of 100Hz the max speed seems better. Is that ok? Motor plate says 50Hz

…

What can be done depends on the physical motor. Jim's plate says the motor normally runs at 1380rpm off a 50Hz supply, which can be taken as it's guaranteed comfort zone rather than an absolute limit.

Increasing frequency will spin the motor faster, dropping the frequency will slow it down. Slowing the motor down and asking it to do hard work risks overheating. But the risk is low on a machine doing intermittent light cuts. Speeding the motor up risks damaging the bearings, and maybe overheating as well because the motor can be pushed by the operator well beyond it's normal power rating. However, 1380 rpm is easy meat for most motor bearings, and I'd be surprised if they gave trouble at twice that speed.

Pushing the motor above normal power is probably OK too, because lathes work intermittently, and – carbide apart – most owners don't take long heavy cuts at high speed. As long as the motor has time to cool between bursts of work, all should be well. (I've never managed to get the motor on my lathe more than luke-warm. ) Three-phase induction motors are tough cookies too, far less vulnerable to abuse than single-phase and brushed DC types.

Might be worth investing in a Portable Tachometer, or Permanent Tachometer. With speed control handy to know what RPM the chuck is actually doing, and it confirms that the Inverter settings are realistic.

The other issue with high-speed is the lathe itself. Most older machines just aren't designed for it. Particularly unwise to over-speed plain bearings and total loss lube systems. Worse if the bearing is driven fast and deep cuts are taken. Probably won't fail spectacularly, instead years are taken off the life of the bearings.

Driven reasonably – no problem. And it sounds as if the broken VFD was already running the motor above 1380rpm without bother. Shame we don't know the old settings, but it's a fair bet. A tacho will tell.

Dave

[Jim Young 2Participant @jimyoung2]

Thanks to everyone for their wisdom. All working happily to a max of 65Hz. I realised that there was a parameter not listed on my instruction sheet (P25) discovered whilst watching a youtube video. It sets the number of poles. It is in the inverter and programmable …..just not listed.

It seems that this vfd is delivered in several different cases but is basically the same electronics inside.

Just for info it is the XSY-AT1 not very expensive, but beware there is no way that the terminals comply to any european (uk) regulations. There are no cable gland holes and the terminals are easy to touch. I am going to mount it inside an IP65 box and gland off the cables now I have everything working from external controls. There is even facility on the VFD to power an external cooling fan. Last job is to get some proper control cable for the pot and the switch, I don’t like using the green / yellow for anything other than earth even if it is only 10v!

[SillyOldDufferModerator @sillyoldduffer]

Posted by Jim Young 2 on 09/05/2020 18:21:18:

…

Just for info it is the XSY-AT1 not very expensive, but beware there is no way that the terminals comply to any european (uk) regulations. There are no cable gland holes and the terminals are easy to touch. I am going to mount it inside an IP65 box and gland off the cables now I have everything working from external controls. …

That's right. Few VFDs are user-facing consumer items. Most need to be enclosed inside an appropriate cabinet, not used out in the open. It's in the same class as the lathe's other protected "don't touch" electrical innards: contactor, fuse-holder, switches and wiring etc. The VFD box is barely more than a dust cover over the electronics. Not suitable for external use, especially in a workshop.

Have to undo six screws from a steel cover at the back to get anywhere near the VFD hidden inside my headstock. It's the cable-glanded and earthed lathe that meets Consumer Regs, not the VFD.

Dave

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