Convert 180vdc to 90vdc?

Thread Starter

reharik

Joined Nov 4, 2019
23
Hi, I'm trying to to find a dc drive that will power a higher horsepower treadmill motor ~3-4hp.
All the drives I've found will be like 1.5hp @ 90vdc/3hp @ 180vdc. But I don't have a 180vdc motor, the motors I'm looking at are all 130vdc.
So I'm not sure what to do about that. Is there a way to take that high vdc and use it for a lower vdc motor?
 

schmitt trigger

Joined Jul 12, 2010
136
Is this a brushed DC motor ?

if so, find a 180vdc controller which has a “Max speed” setup, and adjust it such that at its maximum range, the output voltage is clamped to 130 volts.
 

Thread Starter

reharik

Joined Nov 4, 2019
23

Thread Starter

reharik

Joined Nov 4, 2019
23
Please clarify . Are you looking for a 3/4 hp drive or a 3 hp to 4 hp drive?
Yes I'm sorry, that is unclear. I'm looking for 3hp to 4hp. I can get a motor in that range for relatively cheap. I probably don't need more than 3hp though.
Thanks
R
 

MaxHeadRoom

Joined Jul 18, 2013
20,000
The KBWD-16 is now replaced by the KBWD-15, good for 6amps.
The KB Electronics site list all their products, including the reversing ones.
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
20,000
These DC motor rating are generally based on peak current, 3hp on a 120v/15a outlet is going to exceed the rating, if using a 3HP motor, I would tend to go with a 240v version preferably.
Max.
 

Tonyr1084

Joined Sep 24, 2015
4,146
The residential TM motors I've come across have all been 130 VDC. Some of them were 1.5 to 2.5 HP. I'm assuming their controllers also operated on 130 VDC.

You said:
All the drives I've found will be like 1.5hp @ 90vdc/3hp @ 180vdc.
Are you assuming that if you double the voltage you'll double the horse power? If so - that's a wrong theory.

HP is 745.7 watts. Not amps, not volts, watts. So if you want 2 HP then you need 1491.4 watts. So how many amps is that? Well, wattage is calculated by multiplying voltage times amps. So the inverse would be true as well. Watts divided by amps equals volts and watts divided by volts equals amps. So assuming you're supply is 130 VDC then 1491.4 ÷ 130 = 11.5 amps. That gives you the power for 2 HP.

745.7W x 3HP = 2237.1W (watts). Working with 130 VDC, that's going to be 2237.1 ÷ 130 = 17.2 amps.

That would assume (at 3HP) your motor winding resistance is approximately 130V ÷ 17.2A = 7.6Ω when operating at that level. Resistance will vary as the motor operates at different power levels and speeds as well as loads.
 
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Thread Starter

reharik

Joined Nov 4, 2019
23
Yes that's a good article and lines up with my understanding.
So one point is still unclear.
If I have a motor at say 90vdc, and I get a controller that has
input: 110vac/220vac
output 90vdc/180vdc
HP: 1.5/3
and I hook it up to 220vac what will be the result? I will have to limit output voltage down to 90vdc, at which point, will it not be essentially the same as using the same controller at 110vac/90vdc/1.5hp ? and if so, again I'm limited to 1.5 hp of out put at most from all KB dc drives.
And if above is true the only way to get more of the available power from the motor is to go with a triac scp hooked up to a bridge rectifier. Which while it does not have any of the nice additional features that a kb drive would have, it does give you as much power as you can consume (meaning the motor can consume)
 

MaxHeadRoom

Joined Jul 18, 2013
20,000
I hook it up to 220vac what will be the result? I will have to limit output voltage down to 90vdc, at which point, will it not be essentially the same as using the same controller at 110vac/90vdc/1.5hp ? and if so, again I'm limited to 1.5 hp of out put at most from all KB dc drives.
And if above is true the only way to get more of the available power from the motor is to go with a triac scp hooked up to a bridge rectifier. Which while it does not have any of the nice additional features that a kb drive would have, it does give you as much power as you can consume (meaning the motor can consume)
A 90v motor on 220v will essentially overspeed, Voltage = rpm, Current = torque.
If you measure the DC resistance of the motor, it can tell you the maximum current (torque). Which, BTW is maximum at zero rpm.
To do this properly you need to lock the armature so it does not rotate and apply a small, known DC voltage and measure the current, do this in a few places on the armature and take the highest current reading in order to measure the resistance.
Max.
 
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