Resistance readings expected small single-phase EC motor windings

[Mark_B]

I am building an HVAC system model (see other post) and chose a Bell and Gossett Ecocirc+ 20-18 pump. I got this pump open box on ebay and there is a short return window so I decided to check motor windings resistance upon receipt.

I am used to measuring windings on larger three-phase and capacitor-start single phase motors so this one is new to me. It has just two leads for connecting 120V power then a small terminal for 0-10VDC input. Checking the resistance between these two leads yields a reading around 200k ohms which slowly counts up toward one Megohm. Is this normal?

Would performing an insualtion test on this motor using these leads be possible with the use of an insulation tester applying DC voltage?

 

[Mark_B]

I am building an HVAC system model (see other post) and chose a Bell and Gossett Ecocirc+ 20-18 pump. I got this pump open box on ebay and there is a short return window so I decided to check motor windings resistance upon receipt.

I am used to measuring windings on larger three-phase and capacitor-start single phase motors so this one is new to me. It has just two leads for connecting 120V power then a small terminal for 0-10VDC input. Checking the resistance between these two leads yields a reading around 200k ohms which slowly counts up toward one Megohm. Is this normal?

Would performing an insualtion test on this motor using these leads be possible with the use of an insulation tester applying DC voltage?

My assumption is that the power leads are attached to the commutator and so are electrically insulated form the windings. This would also suggest insulation test cannot be performed using these leads.

I applied power to the pump for just two seconds to hear the impeller spin and it did appear to start normally.

 

[waross]

WOW!
If you don't know what you are doing. DON'T DO IT.

I applied power to the pump for just two seconds to hear the impeller spin and it did appear to start normally.

It passed the test.
That is a Brush-Less-D-C motor. BLDC
The motor is a three phase, permanent magnet synchronous motor.
It is fed by a variable frequency inverter.
The inverter is fed DC.
The DC is developed from the incoming AC line with a bridge rectifier.
There will also be a smoothing capacitor.
The small test current from your meter passed the bridge rectifier and slowly charged the capacitor.
As the capacitor charge increased,the current dropped until at full charge, there was basically no more charging current and thus a high resistance reading.
There is a 0-10 Volt DC input that controls the speed.
If you don't have the components to supply the 10 Volts DC, then RTFI to find out how to run the pump without a 0-10 Volt signal.

If you don't know what you are doing. DON'T DO IT

 

[waross]

Would performing an insualtion test on this motor using these leads be possible with the use of an insulation tester applying DC voltage?

That will probably destroy the electronics.

 

[Mark_B]

WOW!
If you don't know what you are doing. DON'T DO IT.

It passed the test.
That is a Brush-Less-D-C motor. BLDC
The motor is a three phase, permanent magnet synchronous motor.
It is fed by a variable frequency inverter.
The inverter is fed DC.
The DC is developed from the incoming AC line with a bridge rectifier.
There will also be a smoothing capacitor.
The small test current from your meter passed the bridge rectifier and slowly charged the capacitor.
As the capacitor charge increased,the current dropped until at full charge, there was basically no more charging current and thus a high resistance reading.
There is a 0-10 Volt DC input that controls the speed.
If you don't have the components to supply the 10 Volts DC, then RTFI to find out how to run the pump without a 0-10 Volt signal.

If you don't know what you are doing. DON'T DO IT

"I am building an HVAC system model (see other post)." Your response reads "WOW! If you don't know what you are doing, don't build a model at home with your own money to learn!" Thanks for the assistance but man why did you need to package it in a vitriol sandwich.

BTW I will be using a JACE building controller to supply 0-10VDC to modulate pump speed.

 

[Mark_B]

WOW!
If you don't know what you are doing. DON'T DO IT.

It passed the test.
That is a Brush-Less-D-C motor. BLDC
The motor is a three phase, permanent magnet synchronous motor.
It is fed by a variable frequency inverter.
The inverter is fed DC.
The DC is developed from the incoming AC line with a bridge rectifier.
There will also be a smoothing capacitor.
The small test current from your meter passed the bridge rectifier and slowly charged the capacitor.
As the capacitor charge increased,the current dropped until at full charge, there was basically no more charging current and thus a high resistance reading.
There is a 0-10 Volt DC input that controls the speed.
If you don't have the components to supply the 10 Volts DC, then RTFI to find out how to run the pump without a 0-10 Volt signal.

If you don't know what you are doing. DON'T DO IT

Controls/hydronics/Air handling project for deeper learning - input appreciated - HVAC/R engineering

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