Emerson Exchange 365

• Not Answered

Type of charm for 24VDC contactor

I have a 24VDC contactor that I need to turn on/off. What type of charm should I use? I have DO 24VDC and DO HSS available but if I try with the former, nothing happens when I send the on signal. With the DO HSS, the contactor gets activated but it turns off himself.

I'm using a DO block to send the on/off signal.

Any advices?

Carlos Velazquez

• 6 Apr 2017 8:47 PM
• Cancel

6 Replies

• Tinh Phan

  

  • 7 Apr 2017 1:42 AM

  Hello Carlos,  Without knowing your wiring setup and power setup, I am guessing you have having some sort power setup issue.  Here is a commissioning document that ou can verify 24 VDO and HSS wiring and setup verification.  Maybe this will help with troubleshooting your issue. Let me know if your wiring and confirguration is correct and still are having issue.  I will look at other possible cause.

  Commissioning Charms

  • Cancel
• Andre Dicaire

  

  • 7 Apr 2017 7:18 PM

  The DO channels need to be matched up with the steady state power requirements of the field device. So you need to know the power requirements of the contactor to select the right CHARM.
  
  The DO 24VDC High Side is rated for 100 mA steady state, and has a resettable fuse that will trigger at approximately 200 mA. If the starter is drawing more than 100 mA, it may be causing the internal protection of the CHARM to open circuit and this is causing the motor to drop out. The DO 100mA energy limited CHARM operates at a slightly lower voltage and limits current to 100 mA. This CHARM would not provide enough power for the relay.
  
  For Higher current up to 1 Amp steady state, you can use the DO 24VDC Isolated. If you need the CHARM to provide power, you would couple this with the Fused Injected Power Terminal block, which draws field power from the local Baseplate Power distribution. This gives you 1 amp per channel.
  
  If the contactor needs more than 1 Amp, you can use the Relay Output Terminal blocks, which provides Form C contacts rated to 5 Amps (max voltage is 28.8 VDC I think). The Relay terminal block is intended for use with field side powered circuits. It provides an Normally Open and a Normally closed contact. You would use the DO 24 VDC High Side CHARM with this terminal block to drive the relay coil in the terminal block.
  
  DO channels offer the most field options, and require more options on the IO card to adapt to the selected field device. From Voltage type (DC vs AC), system powered vs field powered, and various current options, to Intrinsically Safe, the CHARM IO card lets to match the field requirements by using the matching CHARM/Terminal block.
  
  Once you've got the electrical characteristics of the circuit lined out, the system configuration comes into play. If the DO channel itself can be configured to be Latching (Default), Momentary, or continuous pulse. With motor start commands, a momentary output might make sense, but the starter must be setup to latch the start command. You can also choose to control the Start bit from the control module for a momentary start, and again the starter must be setup to handle this to latch the start command. Once the DO channel configuration is set as you want, you can configure the logic to drive the DO block as needed.

  Andre Dicaire

  • Cancel
• Carlos Velazquez

  

  • 21 Apr 2017 1:34 PM

  In reply to Andre Dicaire:

  Thank you to both for your response. Now, using the information from Andre, I used the DO 24VDC ISO in the FIPT block but the contractor did not get activated or close the circuit. After this, I tried manually and it worked, then I tried the DO HSS and it started but opened almost immediately, so I guess the Contactor is drawing more than the 100 mA.
  Just to check if I'm doing something wrong with the connection or wiring, I connected a pair of cables to the two terminals of the Contactor and the two terminals of the FIPT block where I have the DO 24VDC ISO. Just for reference the contactor is a TP1-D32 10; Shamrock Controls.
  
  Any advices?

  • Cancel
• Andre Dicaire

  

  • 21 Apr 2017 3:00 PM

  In reply to Carlos Velazquez:

  What is the steady state current for the starter. That determines the CHARM needed.
  
  As for why the DO Isolated with FIPT TB did not work, was there power provided to the Baseplate address plug terminal block.
  
  Using a Volt meter, confirm that the DO ISO CHARM is driving the field wiring. If properly powered. The DO ISO drives up to 1 amp.

  Andre Dicaire

  • Cancel
• Carlos Velazquez

  

  • 21 Apr 2017 5:12 PM

  In reply to Andre Dicaire:

  I am not an electrician so please bear this question with me. Do you mean that I have to supply a 120 VAC to the Baseplate address plug terminal block? To be more specific, I would have to run a cable from a 120 VAC source to the positive and negative terminals of the Baseplate address plug, am I right? If I am making no sense, please forgive this ChemE.

  • Cancel
• Andre Dicaire

  

  • 21 Apr 2017 6:23 PM

  In reply to Carlos Velazquez:

  Till now you've been using 24 vdc CHARM types, so why are we talking about 120 VAC?
  
  You should involve an electrician or instrument tech and read the CHARM installation manual to understand the capabilities of the product before you damage anything.
  
  The injected power terminal block connects to a local power distribution bus in the CHARM nameplate. If you need 24 VDC, connect 24 VDC to the address terminal block as indicated in the installation manual. Without this power the isolated DO will not drive the relay.
  
  If you are using the DO VAC CHARM, then you would connect 120 VAC power to the baseplate.
  
  Please get some assistance on the electrical aspects of this installation.

  Andre Dicaire

  • Cancel