Relay and DAQ for switching a DC Motor

[svans5]

Hello..we wish to use SPDT relay with NI USB-6008 DAQ card for switching on/off a DC motor. The DC motor has a voltage rating of 122V and current rating of 10A and it is used to pump water. The SPDT relay we have has voltage and current ratings of 12V and 6A respectively. Can this relay be used to directly control the motor, if the relay is energized from the DAQ? Do we need to connect any other component in order to use this relay?

[RavensFan]

You'll need a couple of relays.  You'll need a motor contactor that has a voltage and current rating on the contacts that work for the motor.  Many of these contactors have a 24V coil that.

You will need a 24V power supply.  Now you need something between the USB-6008 and the 24V contactor.  This might be another relay.  Or perhaps a transistor driver that can take the 5V DC output from the USB=6008 that will control the 24 V DC coil.  A USB-6008 doesn't have enough current capacity (or the voltage) to drive a motor contactor coil directly.

I'd recommend talking to someone familiar with electrical control circuits about your specific requirements.

[aputman]

You can use the DAQ board to remotely operate the power supply.  Most power supplies have a remote programming terminal where you can supply a control voltage (typically 0-5VDC or 0-10VDC) with 5V or 10V equaling full output of the supply.  No relay or driver circuit is required for this.

[RavensFan]

Except he didn't say he had a power supply that was capable of 10A @ 120V.

[aputman]

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@RavensFan wrote:

@Except he didn't say he had a power supply that was capable of 10A @ 120V.

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Thank you Mr. Obvious. 

[aputman]

Sorry Raven.  I mean no disrespect.  But there has to be something supplying power to the motor.  If it is a power supply, my suggestion might work.  If not, so be it.  I don't know the whole situation so i can only offer suggestions and let the OP decide.

[svans5]

The motor is being powered by rectified power supply of 100V.

[RavensFan]

True.  Usually when I hear of 120V, I'm thinking of AC power  that is just directly powered from the lines and you need a basic contactor to connect and disconnect the motor.  For DC motors, there has to be some source of DC power, and whether that is some source of power such as a DC voltage bus within a plant, or a dedicated power supply converting 120 VAC to 120 VDC specifically for that motor, we just don't know.

Either way, we need more details from the original poster, and can agree that a 12V 6A relay is not going to be usable as is.

[svans5]

If we're to use a contactor with relay, what should be its rating and specifications?

[svans5]

Does it mean we cannot use contactors for switching a dc motor? Also this is an institutional level project for building a water pumping system.