Priority Switch - Three Phase

Kevin!

Is it possible to install a priority switch similar to those used for electric showers on three phase car ramps? I'm looking to reduce my maximum import capacity and would like to ensure that the demand does not exceed 29 kVA,


Thanks

Bruthal

Kevin! wrote: »

Is it possible to install a priority switch similar to those used for electric showers on three phase car ramps? I'm looking to reduce my maximum import capacity and would like to ensure that the demand does not exceed 29 kVA,


Thanks

It could be done alright, but is it needed? What are the electric motor sizes?

I wouldnt have thought they would be all that big, since the lifting would be done over a time frame. If it was 3 seconds, it would be a much bigger motor needed than if it was over 30 seconds for example.

Kevin!

I have an Owl energy usage monitor set up to monitor the three phase connection, and with one ramp running it spiked to 13.02kW with one ramp in operation.





It's difficult to measure all ramps at the same time as they are connected to three different electricity meters, the equipment installed is as follows:


Maximum Import Capacity Calculation kW

Computing 0.5
1 IBM eServer 514W 0.5
1 HP Gen 9 Server 500W 0.5
7 Desktop Computers 180W 1.26

Workshop 3 Phase
1 Extractor Fan 0,75 kW 380V 1.9 A 0.75
1 Ramp 1 2.2 KW 400V 50hz 2.2
1 Ramp 2 2.6KW 3 Phase 2.6
1 Ramp 3 3.5 KW 3.5
1 Compressor 4HP 3KW 3
Total 14.81


It's Ramp 3 that is illustrated in the ramp diagram at 13.02kW


Thanks

Bruthal wrote: »

It could be done alright, but is it needed? What are the electric motor sizes?

I wouldnt have thought they would be all that big, since the lifting would be done over a time frame. If it was 3 seconds, it would be a much bigger motor needed than if it was over 30 seconds for example.

Bruthal

It might have picked up the ramp at the time the motor started, to get that large max reading from the ramp. Motors take multiple times the normal running current at the time of startup, as the motor rotor is stopped right at the instant power is supplied to it. But only for a very brief time, the time it takes the motor to start turning.


If it is a 3.5kw motor as stated in the equipment list, then that is its full load demand, which would be about 4.3kva (@ 0.8 pf) of your capacity used while it is running.

Its doubtful a priority unit is needed there.

dodo mommy

Can anyone tell me how to work out the rate per hour for the owl energy monitor. I'm clueless.

LeBash

Could be done with a 3 phase meter that has a settable point for triggering a relay easily enough. Cost a quite a bit to do, so you'd need to be sure it was really necessary?