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07 October 2010

About electromagnetic interference

Posted in Technical papers

..and how to avoid it!

One of the problems using remote ballasts is the electromagnetic interference it can produce. There are very simple ways of avoiding this.

Modern electronic ballasts operate at high frequencies. Working with high frequency equipment can cause electromagnetic interference which can be not only a nuisance but in some cases also a security or safety hazard.

EMI can only happen if the source of the high frequency is not shielded. Remote ballasts are shielded by a metal housing which is connected to earth and the reflector terminal should be shielded as well, but the leads from a remote ballast to a lamp are not shielded. Using shielded cable would in many cases cause problems powering your lamps, so unschielded wire is used for the connection to your lamp. This unshielded wire is the cause of the most problems as it acts like an antenna. So, if you use electronic high frequency ballasts we recommend to keep the leads to the lamp from the ballast as short as possible and install the ballast as close to the lamp as possible.

As our ballasts are solid state and sealed they are safe to use in the growing environment you can mount them near the lamps. The heat dissipation of the electronic ballast is vvery little compared to the lamp and will not reach your plants as it is convection heat. Out Pro 600 ballast for example only dissipates about 35 watts of heat. A HPS lamp generates about 70-75% heat and only 25-30% usable light. In the example of the 600 watt Pro 600 the lamp would account for more than 420 watt of dissipated heat. The ballast adds less than 8% to that. As a rule of thumb you can add about 5-10% of cooling to your room to maintain the same climate with the ballasts installed inside your grow room.

To further eliminate any EMI we recommend to use integrated fixtures as you have no leads between the ballast and the reflector as the ballast is integrated in the fixture. The only disadvantage you might have using an integrated fixture it that you need about 15 cm more height to accomodate the full fixture compared to a remote reflector.Remember we have professional installation of more than 12,000 fixtures on one location. If there would be any EMI those sites would be as powerful as a large radio station. We can assure you they are not.

So, to eliminate EMI there are a few solutions:

1. Best option: Use integrated fixtures. This will eliminate EMI caused by lamp leads
2. If using remote ballasts: keep the leads as short as possible

Our Pro line ballasts operate on 240V. Double the voltage means half the amps! Your mains leads can be much thinner than the leads you would have to use for a remote reflector. So using full fixtures or remote ballasts close to your lamps makes it a lot easier to wire. You can connect more than one ballast on one lead and switch those with a high power contacter.