control power monitor
control power monitor
(OP)
Hey Folks,
Anyone now of a really cheap montior for control power status?
I have a job that has ten feeders with ten separate CPT's on each feeder and the design engineer has requested that the 120VAC secondary of each CPT be monitored... this is lots of $ for something we have never done here before...
I have checked with AB and Carlo Gavazzi and found a couple however they are in the $200-$300 dollar range.
Anyone have experience with this?
Regards,
TULUM
Anyone now of a really cheap montior for control power status?
I have a job that has ten feeders with ten separate CPT's on each feeder and the design engineer has requested that the 120VAC secondary of each CPT be monitored... this is lots of $ for something we have never done here before...
I have checked with AB and Carlo Gavazzi and found a couple however they are in the $200-$300 dollar range.
Anyone have experience with this?
Regards,
TULUM






RE: control power monitor
RE: control power monitor
I am not familiar with what a CPT monitor should do? Is it supposed to warn of a dip in voltage?
A control relay would drop out basically at 30% voltage and pickup again around 80%. Is this an acceptable method in industry for monitoring control...
My thought is - what is required? To let the scada know the Control power is gone, or let the SCADA know that there is a dip and you may loose it?
Regards,
TULUM
RE: control power monitor
If it is to monitor the power and send a signal that power is lost, then a simple relay will work fine.
I would find out what the designer is trying to accomplish.
RE: control power monitor
I am sure that monitoring for voltage dips and recording the time of events is already done at the main panel, on the incoming lines and possibly on the feeders.
Any voltage dips on the feeders will be passed on to the secondaries of the control transformers.
A problem or impending failure that shows up as a voltage dip only on the secondary of a control transformer will certainly develop into a complete failure in a short period of time. Probably before it can be located by the technicions.
Typically monitoring of control power transformer secondaries is used to warn of complete failure of control power. This would be open fuses or breakers and/or a failed control transformer.
I would consider an economical PLC. Connect each transformer output to a seperate input on the pLC.
You would want to verify the threshold voltage of the input interface on the PLC.
With a PLC installed, it will be simple to communicate the status to a DCS or SCADA system.
respectfully
RE: control power monitor
I will look at both options...
RE: control power monitor
RE: control power monitor
There are inexpensive adjustable voltage monitor relays available from plenty of sources, $200-$300 seems grossly excessive. Time Mark has one for less than $100 that plugs into an octal socket, this one needs just one screw in the center and is only about $65.
http://sacramentoelectronics.com/ncc/SSR5-5.htm
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RE: control power monitor
RE: control power monitor
Some schemes wire this "Ready Relay" between the motor overload and the Auto switch so the relay only picks up when the motor starter control circuit is powered, the H-O-A switch is in Auto and the overload protection is OK.
RE: control power monitor
Thanx
Regards
Ralph
RE: control power monitor
respectfully
RE: control power monitor