Controlling Single Phase Reversible Motor with Three Phase Starter

Thread Starter

jhaislip

Joined Aug 17, 2010
2
I have a solid-state three phase reversing contactor (Crydom DRC3R40D420 datasheet) and would like to use it to control a single phase, 6 wire, 120VAC reversible motor (picture of motor info plate attached). When reversed, the Crydom contactor connects L1 to T3 and L3 to T1. From the motor info plate, the BLU, RED, ORG wires should be connected to L1 and the WHT, YEL, BLK wires should be connected to L2. Reversing is achieved by swapping RED and BLK leads.

Is it possible to use this contactor to control this motor? The only way I can think of doing it is shown in the attached diagram. If I wire T2 of the contactor back around to L3, I could connect T1 -> RED, T2 -> (WHT, YEL), and T3 -> BLK. I would then need to wire BLU and ORG directly to L1 (neutral). I believe this achieves the correct connections, but is it safe to wire neutral directly to BLU and ORG and only switch the other motor wires using the contactor?

Thanks!
Josh
 

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MaxHeadRoom

Joined Jul 18, 2013
25,017
If I read your dwg right, you won't get the correct configuration?
I think you will need 4 switching elements not 3.
That is a relatively small motor, is there any reason you would not use a small 3 phase reversing contactor?
Max.
 

Thread Starter

jhaislip

Joined Aug 17, 2010
2
If I read your dwg right, you won't get the correct configuration?
I think you will need 4 switching elements not 3.
That is a relatively small motor, is there any reason you would not use a small 3 phase reversing contactor?
Max.
Thanks Max. Sorry for the poor drawing. The crydom is a 3 phase reversing contactor. The black vertical lines in the drawing represent the state when the contactor is activated in the 'forward' direction. L1 => RED, BLU, ORG and L2 => WHT, YEL, BLK. When the crydom contactor is activated in the 'reverse' direction, the swapping of L1 and L3 is represented by the orange lines. L2 remains unchanged. So L1-> BLK, BLU, ORG and L2 => WHT, YEL, RED. Am I making a mistake? Another concern was with always having neutral on the BLU and ORG lines since they cannot be wired through the contactor.

Are you suggesting I should use some other type of 3 phase reversing contactor? I happen to already have this 3-phase reversing contactor and was hoping there was a way to make it work.

Thanks for the quick reply!
 

MaxHeadRoom

Joined Jul 18, 2013
25,017
From what I can see you would need a four switching paths rather than three, The standard dual 3ph reverser would do it.
I generally use the Telemecanique line, you can pick them up on Ebay.
Max.
 

tcmtech

Joined Nov 4, 2013
2,867
Unfortunately no. As Max said, you need more switching elements to do it.

Two control the main on/off function of the motor and four more would be needed control the forward /reverse function since on a single phase motor the startup direction is entirely dependant on which phasing orientation direction the start winding is in which means it needs to have a H Bridge configured control circuit to select between 0 and 180 degrees relative phase orientation of the start winding.

However if you don't have the main on/off then yes, your 3 phase reversing device would work assuming it can handle the starting current draw of the motor which can be 4 - 6 times the nameplate running current rating.
 
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