Alex wrote:
When motor starting my meter shows 70V momentarily(not sure if it's a true
reading) then goes blank for a second then 108V and stays there while
motor is running with no load.

Is this too much of a drop?

Jerry Martes wrote:
I have been assuming that you are curious to know if your new 1 1/2 HP
motor is working properly. Now you ask if the input voltage as supplied by
your house is adequet for this motor.

Get a voltmeter that connects to your computer and a program to save the
data from its readings. Then it is easy to record the voltage at the input
to the motor as a function of time. Excel will allow you to display a
graph of the line voltage as a function of time. If you get a data saving
program that is fast enough, it is easy to see exactly what voltage is
existant at the motor input terminals at any time.
Or, you can go to a neighbor's house and try the motor there.

If *I* was asked to make a guess at whats wrong with the 1 1/2 HP motor,
I'd guess nothing.

I wouldn't want to run a desktop PC on a supply that drops to 70V. If
its normally about 115V, its dropping to about 60%. That is probably
going to crash the PC. He's posting from a windows box and glitching
the power like that is a good way of scrambling the hard drive. OTOH if
he has a UPS or a laptop, a PC connected meter is a great idea.

The other concern is, what if his excessive voltage drop is cause by a
bad neutral. If that drop to 70V is appearing as a surge to 160V on the
opposite phase and the PC is on that phase I'd reckon on getting some PC
repair/replacement business off him if he was near me.

Beware of the PC scope pods. Many of them are not capable of handling
mains voltages without 100:1 probes (remember its the PEAK voltage that
counts : 1.415 * Vrms) and aren't isolated. OK if the PC is a laptop
sitting on a rubber mat running off its own battery with no other leads
or devices connected to it apart from the scope pod, and if the operator
has the skills to work with a floating scope without winning a Darwion
award. If you are doing data acquisition with mains voltages, an
infra-red keyboad + mouse combo is cheap insurance against getting shocked.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
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