I've got requests to provide inverter backup (UPS) for several 3-phase motors. The motors are considered as critical operation and at present they're supplied by Eskom power are are backed up by generator so during power outages/load shedding the motors stop then auto-restart after a short time period when the generator supply has stabilized. This short downtime has been deemed unacceptable and the power supply needs to be improved to be uninterupted so the supply will be Eskom > UPS > Generator and vice versa upon Eskom supply restore.

All the motors are standard 380-400v 4-pole induction motors and range between fractional horsepower and 2.2kW and are used for air movement so they're not under high mechanical load start. Some of the motors are run by variable speed drives which would require a 3-phase and neutral supply, some are simply configured as direct on line and will run on a 3-phase supply without neutral. All motors would require independant inverters and batteries/UPS's as they're located in different buildings.

 

I've always been a fan of Victron products since the days they were only used in marine applications but I'd like to explore other manufacturers options as well. Can you recommend any other products that are equally suitable for critical industrial applications. 

Thanks in advance.

Hi @Marv

Cheapest option may be to replace the 3-phase VSD's with single phase VSD drives that can supply the 3-Phase motors.

About R3k for a 2.2kw VSD https://cfptechnologies.co.za/product/veichi-ac10/ 

You will then only need to have single phase inverters and as the VSD's can be configured for a soft-start so should be relatively light on the inverters. 

Thanks for the suggestion @Sc00bs, that would definately be an option worth considering.

Deye has three phase inverters: https://www.deyeinverter.com/product/hybrid-inverter-1/sun8-10-12ksg01lp3.html which range from outputing 5kW-12kW.

 

 

Kind of a silly situation - Inverter (VSD) being driven by another inverter - if there was more demand, there might be an integrated solution that would make more sense - grid tied inverter with variable frequency output.

 

Anyway, my actual reason for responding - just cautionary note @Marv . You might be aware if this already, but if you have cause to deal with fans (I assume by 'air movement' you mean a fan of some sort) in future - especially bigger units, they are often high inertia machines and have longish run up times the startup current spike at 6-7x full load amps is accordingly long  - this is particularly true of larger, slower running fans. i.e. they are under high mechanical load start.

Obviously the above goes away with a VSD, I've seen a number of folk bitten with DOL starts on fans.

I agree, an inverter supplied by another inverter, even though they're serving different purposes isn't ideal but they're both bringing something to the table. As you point out an integrated, single inverter solution would be far more elegant and efficient...if only one was available.

On 2022/03/22 at 5:36 PM, Sc00bs said:

Hi @Marv

Cheapest option may be to replace the 3-phase VSD's with single phase VSD drives that can supply the 3-Phase motors.

About R3k for a 2.2kw VSD https://cfptechnologies.co.za/product/veichi-ac10/ 

You will then only need to have single phase inverters and as the VSD's can be configured for a soft-start so should be relatively light on the inverters. 

I good solution as long as there is an external star point. Some motors have the star inside at the windings. The VSD's need to get 220V per winding. I would suggest one contact a place like PhD Powerhouse as the have 3 pH UPSes from small to many kW. Not sure if PSS still make their own UPSes.