Re: (ET) ET test box

["Konstanty, Walter (GE Energy Services)" <Walter Konstanty ge com>]

Geof,
   We still test DC motors at GE using an electrical pump back test
setup which I think will work on these small motors.

- Couple motor to identical motor using a v belt
- Wire motor (to be loaded/tested) thru a 100 amp breaker to 36VDC with
the ET control or a large rheostat capable of 100 amps to vary the volts
to the motor or use 12/24/36 volts from battery banks for 3 steps of
testing with a rheostat.
- The generator is wired thru a 100 amp breaker and contactor (or knife
switch) in parallel with the motor.
- A separate field power supply capable of 45 volts or so and 2-3 amps
to power the generator field separately with a rheostat to vary it.
- Voltmeter across the motor terminals and another one across the knife
switch.  Put an ammeter between the motor and generator to measure load
amps.
 
Theory: The motor is connected to the generator mechanically thru the
belt.  The motor is accelerated to various voltage steps for testing
using the rheostat.  At a voltage level (say 24 volts) you run it no
load (except for windage of generator with knife switch connecting the
motor to the generator open) and make sure the motor is ok (no sparking,
vibration, etc..).  Increase field voltage to the generator until it
matches the motor (voltage across the knife switch goes to 0) at which
point you close the knife switch so now the motor and generator are at
the same potential.   By SLOWLY increasing the field on the generator,
you cause the generator to load the motor and circulate amps.  The
batteries make up the electrical losses.  The ammeter measures the load
and the breakers prevent overcurrent.

  We can surely discuss this "off line" and resend a final version.  The
setup is relatively simple and should work even on these compound
motors.  

...Walt

-----Original Message-----
From: Geof Thompson [mailto:geothompson xplornet com] 
Sent: Sunday, June 05, 2011 9:34 AM
To: elec-trak cosmos phy tufts edu
Subject: (ET) ET test box

Gentlemen
I have a Technical question. I would like to create a test (load) box
replicate the load, of a ET motors so that I can benchtest controller
etc. I have quite a few machine that I need to restore and repair.
I am thinking for a PM motor a large resistor will work, but motors with
field weakening is beyond my limited electrical design capacity. Any
ideas would be welcomed along with suggested values of the components
etc.  To say this another way I am looking to make a test box with
meters and resistors which will look like a motor to the Electrak
controlers. Once I get this going I will be happy to share the design.

Geof 


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