Inverters and electric motors

[Col_T]

I am almost certain that I've asked this before, but can't find when or where so apologies in advance.

 

My understanding is that a 1500w inverter will not run a motor rated at 1500w because the motor has an initial start surge that the 1500w inverter can't supply. Is there a rule of thumb to calculate this e.g. rating of motor times 1.5, or 2.3, or whatever??

[Onewheeler]

Six or seven should be ok. Might get away with less.

[Chewbacka]

21 minutes ago, Col_T said:

I am almost certain that I've asked this before, but can't find when or where so apologies in advance.

 

My understanding is that a 1500w inverter will not run a motor rated at 1500w because the motor has an initial start surge that the 1500w inverter can't supply. Is there a rule of thumb to calculate this e.g. rating of motor times 1.5, or 2.3, or whatever??

Most inverters have a surge rating and a continuous rating, however the surge rating on some cheap inverters is only for mS and will not start a motor.  Some cheap inverters can not even manage their continuous rated output for more than a few mins.  So you need to look at the spec sheet for the inverter.  

 

The start up peak load by the motor is not usually on any spec sheet and it depends on the motor, my fridge takes about 5 amps at 220v (so about 1100w) for over a second when it starts, then almost nothing once it’s running.

Edited August 29, 2019 by Chewbacka

[Jen-in-Wellies]

Fridges do seem to be particularly bad for this. Generally reckoned to need, at a minimum, a 1000W inverter to start a fridge compressor that then runs at around 60W. In contrast, my 1600W Victron inverter would run the old 1300W vacuum cleaner OK. This is before I went to a battery vac. No rule of thumb really. Just try it and see, or ask on here about a particular bit of equipment.

 

Jen

Edited August 29, 2019 by Jen-in-Wellies

[TheBiscuits]

Once again I will suggest sunshine solar.

 

 https://www.sunshinesolar.co.uk/Category/PureSineWave12V

 

All their inverters will spike to twice their rating briefly unlike a lot of the noname ones that quote the spike load as the rating and hidden in the manual tell you to only use them at half the quoted power.

 

You still need an appropriate power for what you want to run, but you can expect these to run at rated power.  I'd suggest going at least one size up from what you think you need.

 

They are good quality at reasonable prices, and my only connection is as a satisfied customer.  I have recommended them to several people who have bought one and are happy with it.  And @mrsmelly who doesn't know if he's happy with it because it's not come out of it's box yet!

[Rickent]

8 hours ago, TheBiscuits said:

Once again I will suggest sunshine solar.

 

 https://www.sunshinesolar.co.uk/Category/PureSineWave12V

 

All their inverters will spike to twice their rating briefly unlike a lot of the noname ones that quote the spike load as the rating and hidden in the manual tell you to only use them at half the quoted power.

 

You still need an appropriate power for what you want to run, but you can expect these to run at rated power.  I'd suggest going at least one size up from what you think you need.

 

They are good quality at reasonable prices, and my only connection is as a satisfied customer.  I have recommended them to several people who have bought one and are happy with it.  And @mrsmelly who doesn't know if he's happy with it because it's not come out of it's box yet!

We too have a sunshine solar 1000w pure sine wave and are very satisfied with it,  does what it says on the tin for not a lot of money.

[Sir Nibble]

Eight times running current is the rule of thumb

[Onewheeler]

1 hour ago, Rickent said:

We too have a sunshine solar 1000w pure sine wave and are very satisfied with it,  does what it says on the tin for not a lot of money.

We too. I tested it recently with the washing machine on cold wash and it ran with no problems even on the spin cycle.

[mrsmelly]

11 hours ago, TheBiscuits said:

Once again I will suggest sunshine solar.

 

 https://www.sunshinesolar.co.uk/Category/PureSineWave12V

 

All their inverters will spike to twice their rating briefly unlike a lot of the noname ones that quote the spike load as the rating and hidden in the manual tell you to only use them at half the quoted power.

 

You still need an appropriate power for what you want to run, but you can expect these to run at rated power.  I'd suggest going at least one size up from what you think you need.

 

They are good quality at reasonable prices, and my only connection is as a satisfied customer.  I have recommended them to several people who have bought one and are happy with it.  And @mrsmelly who doesn't know if he's happy with it because it's not come out of it's box yet!

Very true but I am looking at campervans at the moment so it may end upon that 

[Rickent]

4 hours ago, Onewheeler said:

We too. I tested it recently with the washing machine on cold wash and it ran with no problems even on the spin cycle.

Ours will run our washing machine, which is a Zanussi and very fussy over electricity,  problem is, even on a cold wash, the heater comes on to heat the water to 20 degrees and overloads the inverter. Hand washing then rinsing and spinning in the machine causes no issues.

[TheBiscuits]

11 minutes ago, Rickent said:

Ours will run our washing machine, which is a Zanussi and very fussy over electricity,  problem is, even on a cold wash, the heater comes on to heat the water to 20 degrees and overloads the inverter. Hand washing then rinsing and spinning in the machine causes no issues.

What power rating is your washing machine and what power rating is your inverter?

[wiltshirewonderer]

It depends...... You have peak vs continuous rating on the inverter. You also have to take into account the device e.g. many power tools now have a 'soft start' which minimises or eliminates the startup surge. I happily ran a 2kw electric chainsaw all winter (with soft start) from a 3kva Victron.

[Rickent]

2 hours ago, TheBiscuits said:

What power rating is your washing machine and what power rating is your inverter?

1000w inverter, the heating element is too much for it.