LRVF mod

Hi. I’m doing a traction mod. Old set up has 220 building power stepped up to 480v for Otis drive and motor. Is there any reason to keep the high voltage for new controller and motor ? Holister Whitney and Alpha seem to be fine with the 220v ?

the only reason someone would use high voltage machine / motor is to lower the Amps, what is the existing speed and capacity of the car ? if the HP is greater that 40HP or even 30hp its better to go with high voltage . smaller drive and better price on the controller , the down side is you need a step up transformer .

Only reason to do that would be if the motor voltage is higher than line voltage. Alot of gearless pm motors are in the 300-400v range and if your line voltage is too low, the dc bus won't be able to charge to a high enough voltage to be able to run the motor.

If your going to use a motor especially an induction motor that's the same as line voltage, there's no benefit. Your control transformers are going to kick it down to 120 or less anyhow for all of the controls. And I've never seen a door operator run on higher than 220/240. Most new operators are fine with lower voltage.

And yes, you'd need a step up iso transformer to do this.

The existing motor is 460v 10HP. With FLA= 14.3

100fpm 2500lb cap

HW is giving us a new 208/230/460 20HP motor .
AMPS - 29.2/28.2/14.1

With geared traction machine that says 7.3 HP

Sounds like it can be wired up low voltage and be good to go

But then my amps will be 29.2? Looks like we need the 460v to keep similar FLA ?

This is true, if you halve your voltage and keep your hp the same your amperage will roughly double. I guess it depends on your goals. Is higher FLA bad? Wouldn't you just need to pull wires to the motor a little heavier?

Your FLA amps to the motor would be higher. But if your motor HP is staying the same, the line current supplying the controller would not change. The only change in amperage you'd see is between controller to motor. The old setup the current supplying the controller was just as high before but was being supplied to the transformer primary, and on the secondary side (controller to motor) the amps were lower due to higher voltage. But power consumed is power consumed regardless of voltage.

Sounds like a Solid setup with alpha and HW

Are you going with the GT-11 machine?

Yes GT11.

I just don’t want to trip our main line breaker .. I think we should keep the existing transformer and the 480v to controller. This way amp is same as now

It doesn't make a difference to me what you end up doing, but I think your missing what I'm saying about power being equal. A transformer simply transfers power, it doesn't increase or reduce it. It changes the voltage/current relationship. The amperage is going to be the same through your disconnect regardless of whether you keep the transformer or ditch it. Because the voltage through the disconnect is not changing and the power required is not changing the current is not changing. The previous system only seen a reduction in current on the secondary side of the transformer, which is the controller side. This is why the data tag on a dual voltage motor has 2 amp ratings and 2 voltage ratings but only one HP rating. I'm speaking of Power in the electrical meaning of the word.

Keeping the transformer wouldn't hurt anything, but it is unnecessary. Unless you want to keep it for helping reduce harmonics. But if alpha is supplying a line reactor in the controller(they should be), that is sufficient.

Thanks EE. Got it

There is a couple potential perks to keeping the transformer, such as it serving as an iso transformer to help reduce voltage spikes as well as harmonics and maybe downsizing the drive to save a few bucks and saving a few bucks on motor wiring size

Do you see any issue with keeping the existing Otis transformer ?

I don't think it would be an issue that I can think of. If you have the floor space and it's not a big deal to keep it can provide a couple of benefits. It's not a part that has a high chance of failure. The chance you'll have problems from it are pretty low.


I personally am a fan of remove as much old as possible when doing mods or upgrades though.

So alpha does not have a line reactor in the controller. Is this enough reason to use step up ?

It sort of depends. There's a significant difference on the drive side and line side of a line reactor, if you put a scope on the power wires on either side. the line side is a clean sine wave. The drive side is somewhat a sine wave but very rough with lots of harmonics when the car Is running.

If it was me I'd keep the transformer then. It's definitely worth it for ease of life. There's no real drawback to keeping it but you can rest reasonably assured you wont have power issues since the last car ran with that setup without issues. I wouldn't want to cause any power issues in the building backfeeding harmonics and possibly interfere with other items in the building. And if there was more than one car I'd definitely want isolation in some form to prevent dirty power between cars messing with the drives or other parts of the controller.

That is odd. Most every traction controller I work on with a vvvf drive has a line reactor. I wonder why alphas not using one. Kind of one of those extra steps for top quality you take in advance to prevent problems instead of waiting to see if you have problems. I would at least want some ferrite rings on the power wires going into the drive.

This is the power wires in-between a keb f5 drive and the line reactor, while the car is running

Same car while running, on the other side of the line reactor, in-between the line reactor and iso transformer

Same car, on building side of iso transformer

Thanks EE. Good info brother