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Subject: Re: [LML] [LNC2] Oildyne Hydraulic Pump Inrush
From: Colyn Case <colyncase@earthlink.net>
In-Reply-To: <list-6618310@logan.com>
Date: Thu, 28 Nov 2013 21:23:34 -0500
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Message-Id: <D12C9CA4-C9E1-421D-8671-57AED844042B@earthlink.net>
References: <list-6618310@logan.com>
To: "Lancair Mailing List" <lml@lancaironline.net>

good info.  thanks!

On Nov 28, 2013, at 4:56 PM, John Cooper wrote:

Today I inserted a 75A / 50mV shunt in the power lead to my hydraulic =
pump in order to measure the current draw. I connected my Fluke 87-V =
digital voltmeter on the 600mV range across the sense terminals of the =
shunt . With the pump running in the "gear down" direction and the =
equalization valve open, the motor was drawing a steady 29 Amps. I then =
shut off the pump, closed the equalization valve, and with the Fluke in =
the "250 uS peak" mode, measured the inrush when the pump started up =
again briefly. Would you believe 135 Amps!  (Disclaimer: I purchased the =
shunt on eBay and can't vouch for its calibration.)

Next time the plane is up on jacks, I'll re-do this test in both gear up =
and gear down directions. Also, I intend to temporarily remove the ZNRs =
across the hydraulic relay contacts and measure the voltage spikes with =
no protection.


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