What is the waveform of the current that supplies this pump?

[treez]

Thanks, all power to your bow, I missed the 3/4 inch bit too. The datasheet says it is "self priming up to 3m"......so I presume that is how you knew to have it 4 m total.....to give that bit of margin extra. I would never have thought to have the pump sucking water up 2m as well as blowing water up 2m. Do you think the "sucking water up" bit will make the pump needs to use more energy?
From what you say about the unwanted siphon effect, I think we will need a separate water bucket above the 2m high tube, and a separate riser tube will put water in this, and a separate tube will take water down from this?

 

[treez]

Please could you tell what is the current draw likely to be of the whale gulper pump when the seacock is accidentally left closed?

 

[Dan Mills]

No idea mate, just measure it (I would assume locked rotor, but that will depend on the design of the valves and the possible presence of a pressure relief bypass valve).

Regards, Dan.

 

[treez]

Supposing i said that the power supply that currently comes with this pump has a 24-30v output which is literally PWM'd on and off, such that the voltage at the pump terminals is going up and down as a sqaure wave of 70% duty at period of 75us.......would you say that the pump must be a brushed DC motor, and not a brushless dc motor?

I always though that it was bad to pwm the dc bus to a brushless dc motor?

Strangley, when the pump is supplied with a different (bench) psu at 24v (not being pwm'd on and off) , then the pump current appears to have a slight sawtooth appearance of period some 500us......the sawtoothing tells me that there must be some switching going on in there, as if by a brushless dc inverter, but surely the power supply that comes with the pump wouldnt have been designed to pwm the dc bus to a brushless dc motor?

So the pwming of the dc bus tells me the pump must be a brushed dc motor, but the slight sawtoothing of the pump current when supplied with 24vdc (at 100% duty) tells me that it is possibly a brushless dc motor, unless its a dc motor with a on/off transistor switch mounted with it...turning its current supply on and off?

do you think its a brushless dc motor , or a brushed dc motor?

 

[Dan Mills]

Treez, THINK for a moment...

How is the armature of a brushed machine commuted?
Right, so as the thing spins, new sections of winding are brought into the armature circuit as the shaft turns.
Now what happens to the current when you connect a coil across a supply, possibly you get a ramp up (even if only due to the leakage inductance)....

Some sawtooth in the current of a brushed machine should not really be a surprise, and I can think of a couple of ways to make supply PWM to a BLDC driver work as well.

Why don't you just take one to bits to see how the motor is controlled, a bench vice and a saw would probably reveal all very quickly?

Regards, Dan.

 

[D.A.(Tony)Stewart]

Ask customer to measure input resistance between leads with Ohm meter in both directions to prove it is a 1/16 HP BLDC, which is what I would expect for reliable marine DC motors. But if the resistance is near 1 Ohm bidirectional ( turn to ensure not on edge of commutator) then that resistance will determine your peak start current. THe brochure says it is Ignition protected ( thermal breaker)

I still think best option is supply a small battery with DC charger on float voltage using Ceter tap option of half or full rect. output of 14 or 28 with 2 or 4A trickle charger to handle average current and make it guaranteed never to fail in 10 yrs.

You wouldn't want it to fail as a head pump in case it got clogged. .i.e. not grey water.

Besides it is designed for automotive battery voltages, so it will have more torque at 28V than any 24V SMPS and should be more reliable.
AWG16 or better.

 

[treez]

thanks, we only have one so cant take it to bits, so you mean if I measure approx. 1 ohms then its a brushed dc motor, and if I measure open circuit with the ohmmeter then its a BLDC motor?
By the way the datasheet says its reverse polarity protected, so it must have a diode in it probably.

When supplied with 24VDC at 100% duty the motor current does not go to zero, so for me, this is a brushed DC motor...you agree?......when I looked at the input current to BLDC fans the current is a train of trapezoids, and obviously with zero current in between the trapezoids....the zero current "dead time" bits point to a BLDC, the lack of this in our pump tells me this is a brushed DC motor?

Lets face it, a Brushless DC motor gets supplied by an inverter, and there are times when all inverter transistors are off, and thence no current is being drawn by the bldc.....the lack of this in our pump motor tells me that this is a Brushed DC motor..

If it is a Brushed dc motor, then we will supply it by PWM'ing the DC supply to it at approx. 20KHz......this way, we can limit the current to it, and thence design a smaller , less powerful smps to power it, safe in the knowledge that we will not get overcurrent and subsequent smps output voltage dropout....(and then the subsequent unwanted overload shutdown)

As such, if a brushed dc motor, we would effectively be driving the motor coil as a buck inductor....with cycle by cycle current limiting.

I am amazed that there is no emc problem with PWM'ing the supply to a brushed dc motor (if that's what it is).
The fact that the supply goes to zero so quickly in the off periods of the pwm tells me that there's little or no input capacitance in the motor casing

 

[D.A.(Tony)Stewart]

thanks, we only have one so cant take it to bits, so you mean if I measure approx. 1 ohms then its a brushed dc motor, and if I measure open circuit with the ohmmeter then its a BLDC motor?
By the way the datasheet says its reverse polarity protected, so it must have a diode in it probably. for the MOSFETS or to prevent pumping in reverse if brushed

When supplied with 24VDC at 100% duty the motor current does not go to zero, so for me, this is a brushed DC motor...you agree?. NO brushed will arc and spike past zero even with transzorb. BLDC 3 phase will be steady current low noise. . .....when I looked at the input current to BLDC fans the current is a train of trapezoids, and obviously with zero current in between the trapezoids....the zero current "dead time" bits point to a BLDC, the lack of this in our pump tells me this is a brushed DC motor? Small fans are often 2 phases & 4 stopping positions

Lets face it, a Brushless DC motor gets supplied by an inverter, and there are times when all inverter transistors are off, and thence no current is being drawn by the bldc.....the lack of this in our pump motor tells me that this is a Brushed DC motor. I suspect 3 phase full bridge.

If it is a Brushed dc motor, then we will supply it by PWM'ing the DC supply to it at approx. 20KHz......this way, we can limit the current to it, and thence design a smaller , less powerful smps to power it, safe in the knowledge that we will not get overcurrent and subsequent smps output voltage dropout....(and then the subsequent unwanted overload shutdown)

As such, if a brushed dc motor, we would effectively be driving the motor coil as a buck inductor....with cycle by cycle current limiting. ( Coil+ contact R )

I am amazed that there is no emc problem with PWM'ing the supply to a brushed dc motor (if that's what it is).
The fact that the supply goes to zero so quickly in the off periods of the pwm tells me that there's little or no input capacitance in the motor casing

See comments a in bold

Get a good 14 or 28V ceramic plate lead acid battery and 50W trickle charger.

 

[FvM]

One point asks for contradiction. The motor is described as diaphragm pump with valves, means that the pumping direction can't be electrically reversed. Thus there's no obvious purpose of polarity protection in case of a brushed DC motor, as previously mentioned.

I appreciate Dan Mills saw suggestion, if you don't trust in intelligent methods to identify the motor type. Guess a brushed DC motor would reveal by it's sound in most cases.

 

[D.A.(Tony)Stewart]

Treez, THINK for a moment...

How is the armature of a brushed machine commuted?
Right, so as the thing spins, new sections of winding are brought into the armature circuit as the shaft turns.
Now what happens to the current when you connect a coil across a supply, possibly you get a ramp up (even if only due to the leakage inductance)....

Some sawtooth in the current of a brushed machine should not really be a surprise, and I can think of a couple of ways to make supply PWM to a BLDC driver work as well.

Why don't you just take one to bits to see how the motor is controlled, a bench vice and a saw would probably reveal all very quickly?

Regards, Dan.

No need to take apart, the DCR is self evident on a brushed armature, but a MOSFET bridge is not conducting much in a Ohmmeter bias.

 

[treez]

thanks, so all we have to do is put an ohmmeter on the terminals and if its low resistance eg 1 ohm then its brushed dc motor?

I must admit, this thing is already being driven by pwm'ing its dc supply on and off........doing that for a brushless dc motor was, I thought, very , very bad news......even if you can get away with it its certainly not adviseable at all?

 

[treez]

ohmmeter across terminals of motor reads 1.4 ohms...so this must be a brushed DC motor.?

 

[treez]

This is a new question concerning this Whale Gulper pump, so I decided it is best placed here.

Supposing we supply the whale gulper 220 pump with 6VDC, then how do we know that it won't stall? I mean, it doesn't stall in the lab, but as the pump ages, surely there will be a certain DC voltage at which the pump will stall?
Do you know what is this DC voltage?

Also, presumably, when operated at low voltage, the pump has more chance of stalling when also operated with the maximum discharge head and suction lift distance ?(ie 4 metres & with the narrower 3/4 inch piping). Do you agree?

We don't want the pump to stall, as then it has no back EMF, and just looks like a 1 ohm load to the SMPS...this represents an overload and will make the SMPS shut down on its overload protection.

Whale Gulper 220 pump datasheet:
https://www.defender.com/pdf/503200_Whale_Gulper220.pdf
Whale gulper 220 pump details
https://www.defender.com/product.jsp?...234&id=1777934

 

[D.A.(Tony)Stewart]

It seems to be a brush type pump with 24V across 1.4Ω Rs.

The current will rise according to motor inductance as TORQUE increases with current as it rises towards 17A ( but not reaching that ) . When stiction is overcome back EMF reduces the current and raises the apparent impedance.

Dry running current is rated at 1.2A with a full load fuse rating of 2.5A.
Running with 6V across 1.4Ω would give over 4A and that should start.

The unknown is gear stiction with aging, so it is hard to know the lower starting voltage threshold.

 

[treez]

Thanks, but will the motor stall with a mere 6V power rail connected to it?
I know that a new motor of this kind can start on 6v, but is there a chance of subsequent stalling?, and does the possible incidence of such stalling increase as the suction lift and displacement head increases? (piping length increase)