Subject: RE: Question about capabilities of PC5-120B measuring chopped waveforms

From: "Nick Gayeski" <[email-masked]>
Date: Sat, 6 Dec 2008 00:17:42 -0500

Cory,

The P-series looks like it should work.  Could you give us prices and lead
times on the P-142B as well as a P-special with a 15 amp RMS current rating?

Before we commit to this path we have some questions to ensure that our
solution is a simple matter of frequency limitations and current
limitations.  I have attached images of the compressor and condenser fan
current and voltage waveforms for reference.  The voltage waveforms are
typical PWM square waves phase to phase and a PWM reconstructed sinusoidal
wave phase to neutral (see attached).  The current and average voltage
frequencies for both are between 100 and 400 Hz.  We have read that even
PC5s should work between 40 and 400 Hz in the operation and calibration
manual.  However, the carrier frequencies for the inverters seem to be
around 10-15 kHz.  Also, the PCB-120B is correctly sized so we have
confirmed that the PC5s do not work for these waveforms even with the
correct current rating.

1)       Will the P-series be able to handle this carrier frequency and the
types of waveforms in the attached doc?

2)      Why can't the PC5 handle these waveforms?  Are the internal
transformers bandwidth limited?

3)      On the AC Watt transducer description/specification doc, it lists
0-150 input voltage.  Is this RMS phase-to-neutral? Or phase-to-phase?

Thank you for your support.

Regards,

Nick

Nick Gayeski

PhD Candidate

Building Technology, MIT

617-835-1185

 

From: Cory Forler [mailto:[email-masked]] 
Sent: Wednesday, December 03, 2008 3:10 PM
To: [email-masked]
Cc: Dominick Piccinich; Ansul Robb
Subject: RE: Question about capabilities of PC5-120B measuring chopped
waveforms

Nick,

Check out the P- series online, since your freq range is 120Hz-360Hz.

We will standby for your reply for quoting. 

Cory Forler   PRODUCT TECH SUPPORT 

Ohio Semitronics, Inc.    

4242 Reynolds Dr.   

Hilliard, OH. 43026 

Tel: 614-527-0475 Fax: 614-777-4511  www.ohiosemitronics.com 

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-----Original Message-----
From: Ansul Robb 
Sent: Wednesday, December 03, 2008 2:11 PM
To: Cory Forler
Subject: FW: Question about capabilities of PC5-120B measuring chopped
waveforms

Cory,

Can you help them?

Thanks

Ansul Robb

  _____  

From: Nick Gayeski [mailto:] 
Sent: Wednesday, December 03, 2008 2:00 PM
To: Ansul Robb
Cc: 'Peter Ross Armstrong'
Subject: Question about capabilities of PC5-120B measuring chopped waveforms

Ansul, Corey,

Thank you for your support.  We are trying to measure the power consumed by
a 3 phase variable speed compressor where the speed is controlled by a pulse
width modulated voltage signal.  It is the compressor on a Mitsubishi Mr.
Slim MUZ-A09NA outdoor unit heat pump.  The attached document shows the
current measured on one of the phases and the voltage measured from that
phase to a virtual ground.   The voltage supplied to the motor is created
from a 4.5 kHz carrier through voltage and/or pulse width modulation.

Is this a signal that the PC5-120B should be capable of measuring?
Presently, we cannot make sense of the output from the PC5-120B.  There is a
significant amount of noise in the output, and the output does not seem to
vary with compressor speed (which it should as power consumption increases).

Thanks again,

Nick

Nick Gayeski

PhD Candidate

Building Technology, MIT

617-835-1185