Hello There,

I am in search for a solar inverter suitable for running two 3HP induction motors (one after another). Currently I have Axpert VM III 5KW, which sometimes restart while starting one motor. The reason I believe due to high inrush current.

Upon consulting with some technician, they said these high frequency inverters are not suitable for induction motors. They said to go for any transformer based inverters.

I would like to ask you experts here, which type of inverters are best for running induction motors? transformer based low frequency or high frequency?
Among these two which one can be used for long duration. Moreover can you suggest few brands and model?

Regards,
Rajkumar

forgot to ask, can a VFD be used for the motors to check the high inrush current?

Transformer based (ie low frequency) inverter would be the way to go, eg victron inverters. 

 

Alternatively, you can use the capacitor based non transformer inverters (high frequency), eg your current one, all the Sunsynks etc, but you'll have to size them up significantly to cater for the entire inrush current.

Or you can use a soft starter device to reduce that inrush current. 

Edited June 11, 20242 yr by abd7

1 hour ago, rajkumar.b said:

3HP induction motors (one after another)

What type of induction motor are you using? Any single phase motor with separate start winding, start capacitor or centrifugal switch is not compatible with a vfd. Soft starters can be used in your case. I would not use a 5kw inverter to run a 3hp(2200w) motor as your start power will exceed ~6kw. In your application i would recommend using a 8kw inverter. Even when using low frequency inverter you will still need 8kw for your application. Below details of company that specializes in soft starters.

EMHEATER

Coenraad Swanepoel - B.Eng / MBA

Executive Director

+27 (0)82 888 2417

[email protected]

www.emheater.co.za

www.tcgc.co.za

 

11 hours ago, rajkumar.b said:

I would like to ask you experts here, which type of inverters are best for running induction motors? transformer based low frequency or high frequency?
Among these two which one can be used for long duration. Moreover can you suggest few brands and model?

If you go the low-frequency route, try looking for models from Victron, MLT, Microcare or SMA. Not an endorsement of any particular manufacturer.

12 hours ago, rajkumar.b said:

Hello There,

I am in search for a solar inverter suitable for running two 3HP induction motors (one after another). Currently I have Axpert VM III 5KW, which sometimes restart while starting one motor. The reason I believe due to high inrush current.

Upon consulting with some technician, they said these high frequency inverters are not suitable for induction motors. They said to go for any transformer based inverters.

I would like to ask you experts here, which type of inverters are best for running induction motors? transformer based low frequency or high frequency?
Among these two which one can be used for long duration. Moreover can you suggest few brands and model?

Regards,
Rajkumar

Can you share the actual application. Starting induction motors one need to consider the actual start load as in the torque to move the load. 

If the motors have a massive/heavy load to move like a loaded conveyor it is more difficult to move than say a water pump or fan. 

This has a bearing on the type of gadget to use to reduce start power. 

Running 2 after each other does this imply both run at the same time? 

Edited June 12, 20242 yr by Scorp007

I have a Wolf Typhoon 2600W lawn mower and used it before during LS with other house loads my Deye 8kw doesn't even blink an eye.

2 hours ago, TaliaB said:

I have a Wolf Typhoon 2600W lawn mower and used it before during LS with other house loads my Deye 8kw doesn't even blink an eye.

Some further examples using 1 ph induction motors. 

0.375kW pressure pump from a 0.75kW 12V brick inverter

0.75kW caravan mover from 1.5kW 12V brick inverter

1.5kw steel cutter(brush motor) starting via about 75V SCR controller from a 2.4kW 24V Axpert

1.2kW table saw(brush motor) via SCR controller on the same 24V Axpert. 

The important thing is to find the lower voltage that can overcome the starting voltage(torque) needed. If it does not turn from the word go the windings take a strain and given enough time they will overheat. 

Brush motors normally start turning from about 30V upwards. 

Always surprised to read about people battling to start their motors. Actual load must just be managed when starting it. 

 

Edited June 12, 20242 yr by Scorp007

3 hours ago, Scorp007 said:

Actual load must just be managed when starting it. 

A squirrel cage induction motor will take a certain amount of current to start - and that is dictated by the design. The time it takes that current can vary by load.

4 hours ago, P1000 said:

A squirrel cage induction motor will take a certain amount of current to start - and that is dictated by the design. The time it takes that current can vary by load.

My point was the load on the inverter to be managed when starting some motors. Must have the needed spare output available during the 1st few seconds.