Junos OS

Hi,

The URL gives a brief introduction about Juniper MX480 AC power supply.

My question is:

1. How to differentiate normal AC PS and high capacity AC PS from the model number?

2. MX480 supports low-line and hight AC power configuration, how to identify this is low-line config or high-line config?

Thanks,

Bo

Here's a PDF that goes over the high capacity power supplies for the MX-series.

http://www.juniper.net/techpubs/en_US/release-independent/junos/information-products/topic-collections/hardware/mx-series/common/mx-series-fan-tray-power-supply-upgrade.pdf

Regarding low-line versus high-line, that depends on if you plugged the power supply into a 120V outlet or 208/220/240V outlet.  120V is low-line, the 208V is high-line.  

Look at "show chassis power" to see the power output of the power supplies.  You'll see a line with "Capacity" on it.  That tells you how much power it is capable of supplying.  On a 120V connection it will be around 1400W, probably less.  On a 208+V connection, it will be 2050W or more.

This shows I have four power supplies, all running in high-line mode.

show chassis power 

PEM 0:
  State:     Online
  AC input:  OK (1 feed expected, 1 feed connected)
  Capacity:  2050 W (maximum 2050 W)
  DC output: 171 W (zone 0, 3 A at 57 V, 8% of capacity)

PEM 1:
  State:     Online
  AC input:  OK (1 feed expected, 1 feed connected)
  Capacity:  2050 W (maximum 2050 W)
  DC output: 228 W (zone 0, 4 A at 57 V, 11% of capacity)

PEM 2:
  State:     Online
  AC input:  OK (1 feed expected, 1 feed connected)
  Capacity:  2050 W (maximum 2050 W)
  DC output: 171 W (zone 0, 3 A at 57 V, 8% of capacity)

PEM 3:
  State:     Online
  AC input:  OK (1 feed expected, 1 feed connected)
  Capacity:  2050 W (maximum 2050 W)
  DC output: 348 W (zone 0, 6 A at 58 V, 16% of capacity)

System:
  Zone 0:
      Capacity:          4100 W (maximum 4100 W)
      Allocated power:   1441 W (2659 W remaining)
      Actual usage:      918 W
  Total system capacity: 4100 W (maximum 4100 W)
  Total remaining power: 2659 W

Regarding part number, this is from show chassis hardware

> show chassis hardware 
Hardware inventory:
Item             Version  Part number  Serial number     Description
PEM 0            Rev 09   740-029970   xxxxxxxxxxx       PS 1.4-2.52kW; 90-264V AC in
PEM 1            Rev 09   740-029970   xxxxxxxxxxx       PS 1.4-2.52kW; 90-264V AC in
PEM 2            Rev 09   740-029970   xxxxxxxxxxx       PS 1.4-2.52kW; 90-264V AC in
PEM 3            Rev 09   740-029970   xxxxxxxxxxx       PS 1.4-2.52kW; 90-264V AC in

Cheers!

-Chad

I have another interesting demand regarding low-line and high-line AC inputs on MX480 chassis.The official documentation is referencing 3+1 PEM redundancy , so I can have an extra PEM inserted in the chassis. But how do you secure such a chassis regarding AC input failure ?

In DC mode, you have a 2+2 redundancy so you can cable your PEMs following the ABAB pattern where A and B are different power input arrivals. 

How will a MX480 chassis cabled in ABAB mode behave with A and B , AC low line inputs , in cas of disruption of A or B ?

yes, very interesting question. Hope someone can answer that.

MX480 is a single power zone.  That means all of the power supplies are sharing the load.  My guess is it will depend on how much power is allocated.

Look at the output of show chassis power and see what the allocated power is.  Here is what I show for high power.

> show chassis power 

PEM 0:
  State:     Online
  AC input:  OK (1 feed expected, 1 feed connected)
  Capacity:  2050 W (maximum 2050 W)
  DC output: 171 W (zone 0, 3 A at 57 V, 8% of capacity)

PEM 1:
  State:     Online
  AC input:  OK (1 feed expected, 1 feed connected)
  Capacity:  2050 W (maximum 2050 W)
  DC output: 228 W (zone 0, 4 A at 57 V, 11% of capacity)

PEM 2:
  State:     Online
  AC input:  OK (1 feed expected, 1 feed connected)
  Capacity:  2050 W (maximum 2050 W)
  DC output: 171 W (zone 0, 3 A at 57 V, 8% of capacity)

PEM 3:
  State:     Online
  AC input:  OK (1 feed expected, 1 feed connected)
  Capacity:  2050 W (maximum 2050 W)
  DC output: 348 W (zone 0, 6 A at 58 V, 16% of capacity)

System:
  Zone 0:
      Capacity:          4100 W (maximum 4100 W)
      Allocated power:   1441 W (2659 W remaining)
      Actual usage:      918 W
  Total system capacity: 4100 W (maximum 4100 W)
  Total remaining power: 2659 W

Since my allocated power is only 1441 W, and two PEMs in high power mode provide 4100 W, I take that to mean the system can drop two PEMs without a problem.  It should be able to run on a single PEM since the high power PEM capacity of 2050 W is greater than the 1441 W allocated.  Unfortunately the MX480 is live so I can't confirm if that is true or not.  Based on what I recall of the MX960 behavior when it was a single zone (before the high capacity power supplies), I'm fairly confident that it will behave as I expect.

MX960 with the high capacity PEMs is zoned, so where A & B power go matters.  PEM 0 and 2 support a zone, and PEM 1 and 3 support a zone.  So on the MX960 using A & B power, it needs to be connected A, B, A, B.  When the MX960 was running with a single power zone which ones were A or B didn't really matter.  Same should be true for the MX480 since it is also a single power zone.

Remember, this is an educated response, not a definitive answer.  For a definitive answer, check with JTAC and / or test yourself.

-Chad