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DCB · 08-20-2020, 07:07 PM

Saw these comments on another site.

Person A
“The only problem with this is, say your batteries are low, and you need 120 volts from either a pedestal or a generator to get your charger/converter to charge the batteries, how do you get enough DC voltage to close the contactor in the transfer switch?“

Person B
“Person A has a point about it being preferable to use 120 VAC line power to control the coil. There are a few other options if you want to use AC line power but use DC coils for better contact life and reduced humming. One option is to install a full wave bridge rectifier on the AC power going to the coil, then use a 125 VDC coil. Another option, if you want to scrounge parts from medium voltage motor controllers, is to use a contactor economizing module. The CEM takes in 120 VAC power going to control the coil. Initially when it receives power it passes rectified 120 VAC to the coil, then after a few seconds it drops the voltage down to maybe 20-30 VDC, I don't recall exactly. This prolongs the coil life and eliminates the humming.“

I’m in over my head, but would like to do further research. Can any of you speak to this from your own experience as to whether Person A’s issue is significant? And/or can any of you translate Person B’s response into plainer English?

Thanks!

08-20-2020, 07:07 PM	#18
DCB Seasoned Camper Join Date: Sep 2018 Location: Bloomington Posts: 57 M.O.C. #22743	Saw these comments on another site. Person A “The only problem with this is, say your batteries are low, and you need 120 volts from either a pedestal or a generator to get your charger/converter to charge the batteries, how do you get enough DC voltage to close the contactor in the transfer switch?“ Person B “Person A has a point about it being preferable to use 120 VAC line power to control the coil. There are a few other options if you want to use AC line power but use DC coils for better contact life and reduced humming. One option is to install a full wave bridge rectifier on the AC power going to the coil, then use a 125 VDC coil. Another option, if you want to scrounge parts from medium voltage motor controllers, is to use a contactor economizing module. The CEM takes in 120 VAC power going to control the coil. Initially when it receives power it passes rectified 120 VAC to the coil, then after a few seconds it drops the voltage down to maybe 20-30 VDC, I don't recall exactly. This prolongs the coil life and eliminates the humming.“ I’m in over my head, but would like to do further research. Can any of you speak to this from your own experience as to whether Person A’s issue is significant? And/or can any of you translate Person B’s response into plainer English? Thanks!