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I’m setting up a little self-service laundry mat (in Spain) composed of 3 washers and 2 dryers all having 3 phase motors running at 380V.

The washers consume 1,5kw 2kw and 2,5kw while both dryers consume 0,8kw each. The rest of appliances, UPS, lights, fans, AC outlets, etc., run on 220V off of one of the 3 phases.

The electrical technician has suggested installing a 3 phase capacitor bank to compensate for the “Reactive power” produced by the motors because if not, I may be penalized economically by the local electrical company.

I doubt the 5 motors will be running all at the same time but, just in case they will, should I really be worried about the possible reactive power? Because if so, I’ll take steps to prevent any problems caused by said motors.

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    \$\begingroup\$ Don't know about the regulations in Spain, but in the US the utility companies can't be bothered with monitoring power factor on such a small potatoes customer. They're more concerned with the guys whose electric bill to just run the dust collectors for a month is $10k. \$\endgroup\$
    – Matt Young
    Commented Sep 27, 2015 at 16:26
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    \$\begingroup\$ Matt Young's comment suggests that, rather than ask strangers on the internet, most of whom don't live in Spain (let alone your town), you're probably better off asking your power company. \$\endgroup\$
    – WhatRoughBeast
    Commented Sep 27, 2015 at 17:11
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    \$\begingroup\$ In all honesty, I suspect your electrician is trying to sell you something you don't need. \$\endgroup\$
    – Matt Young
    Commented Sep 27, 2015 at 19:10
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    \$\begingroup\$ You "may be charged"...that's what we call "weasel words". Best thing is to find out for sure. \$\endgroup\$
    – gbarry
    Commented Sep 27, 2015 at 19:16

2 Answers 2

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The electrical technician has suggested installing a 3 phase capacitor bank to compensate for the “Reactive power” produced by the motors because if not, I may be penalized economically by the local electrical company.

That's all fine and dandy if you are running your appliances all together 24 7 but, in the dead of night, ask yourself, what is that bank of capacitors doing?

Answer - they are taking reactive current that they are hoping would balance the reactive current taken by the motors BUT the motors are not switched on SO, if your utility company can bill you extra for having a poor lagging power factor then they surely will bill you for having a poor leading power factor for all those hours that the laundry is shut.

Maybe the electrician has in mind some clever caps that automatically switch in and out or maybe he means installing several sets so that each only activates when their particular motors start turning? Either way, seek clarification from him and if he falls down at the first hurdle then fire him.

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Since you don't have factory, but a laundry, the reactive power is compared with a house. For such small consumer the electric copmanies usually don't charge the reactive power (look in the bill) even so, the power factor corrector cabinet with regulator and switching bank of capacitor + cost of installation is far more expensive than the reactive power bill. You should calculate when this investment will turn over.

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