Solenoids
Last Post 02 Jul 2015 09:51 AM by Mike McGregor. 2 Replies.
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Yashodhar Kahate
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Posts:1

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22 Jan 2015 09:57 PM
    Friends, I have DC solenoids designed for 24VDC. I find they heat up a lot during operation. Can I use the solenoids with 230Vac as they are? What can be the consequences? Will they work? The idea is to reduce the heat generated, assuming they will draw less current at 230Vac for the same load.

    Please advice.
    jwd217
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    07 Feb 2015 05:10 PM
    I would not assume that the current would be less at 230vac for a solenoid made to run at 24vdc. It will probably be much more and melt the wiring. Although changing from dc to ac would have an effect on the amount of current but would be very difficult to know without measuring it. The amount of current through a coil of wire for a dc voltage is only the wire resistance. For an ac voltage it would be effected by the magnetic properties of the core. AC solenoids tend to run cooler then dc because of how they work. When current is first switched on for an AC solenoid the core is outside of the coil. It draws a lot of current and creates a strong magnetic field. Once the core is drawn into the coil, the magnetic properties cause the coil to draw much less current and the magnetic field to drop. But, since the core has already been pulled, it needs less current to hold it in the activate position. I would just look for an equivalent ac solenoid that might run cooler.
    Mike McGregor
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    02 Jul 2015 09:51 AM
    Don't forget Ohm's law. If you increase the voltage, you increase the current, not decrease it. The solenoid creates a magnetic field within the former. In the case of a relay or contactor, the former is attracted towards the solenoid. The current induced in the former sets up another magnetic field that opposes the initial one (mutual induction). This serves to REDUCE the initial current surge following switch-on. If your solenoid is getting too hot, then the current is not being reduced enough. In the case of a solenoid valve, make sure that the solenoid fits snugly over the former, if not the you have the wrong solenoid for the valve. If your application is a relay, make sure it is not jammed, the former must be free to move towards the solenoid.
    Usually AC solenoids have a remanence ring to help sustain the magnetic field as the current reduces to zero (it passes through the zero point 100 times a second on a 50Hz supply). Otherwise your relay would chatter. So AC solenoids can be used for DC, but using DC solenoids for AC can be problematic. The change from 24 to 230 is unwise.


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