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  #21  
Old 05-24-2012, 05:56 AM
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Default Re: Curtis 1238, AC 50 Sluggish Performance

The 144V Curtis is no secret, there is still some question as to what the max current will be, I think it's limited to 500 amps, instead of the 550 or 650 of the 120V 1238-7501 and 7601.
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  #22  
Old 05-24-2012, 06:19 AM
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Default Re: Curtis 1238, AC 50 Sluggish Performance

Dragonsgate said "Even though Bryan at HPEV told me some of what was coming I am not sure if he wanted me to start blabbing about it."
JRP3 said "The 144V Curtis is no secret, there is still some question as to what the max current will be, I think it's limited to 500 amps, instead of the 550 or 650 of the 120V 1238-7501 and 7601." Dragons gate says "Boy! that is a load off my mind."

Last edited by dragonsgate; 05-24-2012 at 06:21 AM. Reason: redundant sentence
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  #23  
Old 05-24-2012, 03:50 PM
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Default Re: Curtis 1238, AC 50 Sluggish Performance

Quote:
Originally Posted by ricklearned View Post
I was at an EV show in LA a couple of weeks ago and heard a similar thing from the people at Curtiss. They told me that HPEV had a couple of 144v controller prototypes for evaluation. They did not tell me to keep it to myself. On this Friday I am going to Ontario to pick up my AC35 package that I ordered from Thunderstruck. While there I will ask how the evaluation is going. I'm a noobie so I am sure I won't pick up on the technical stuff like our more experienced posters.
500amp @ 144/160vdc 12v contactor makes AC-50 really sing
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  #24  
Old 05-24-2012, 05:06 PM
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Default Re: Curtis 1238, AC 50 Sluggish Performance

1238-7601 at 650 amps x 120V = 78KW
The new controller at 500 amps x 160V? = 80KW, not that impressive even if it can actually run at 160V.
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  #25  
Old 05-24-2012, 07:35 PM
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Default Re: Curtis 1238, AC 50 Sluggish Performance

Quote:
Originally Posted by JRP3 View Post
1238-7601 at 650 amps x 120V = 78KW
The new controller at 500 amps x 160V? = 80KW, not that impressive even if it can actually run at 160V.
Well, 80kW isn't great, but it isn't that terrible either. To put those figures into perspective, the Nissan LEAF is also 80kW with a single fixed gear ratio. I would think an 80kW motor mated to a manual transmission should yield pretty respectable performance as long as the vehicle isn't too heavy. The LEAF isn't particularly light and it still has some punch off the line.

I just wish there were some more competition and choices in the AC realm.
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  #26  
Old 05-24-2012, 08:03 PM
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Default Re: Curtis 1238, AC 50 Sluggish Performance

I'm not saying the 80KW isn't good, I'm saying that claiming the new Curtis controller, (which might only add 2KW or so), makes a big difference with the AC50 is dubious at best.
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  #27  
Old 05-25-2012, 04:52 AM
Hippie Djohn Hippie Djohn is offline
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Default Re: Curtis 1238, AC 50 Sluggish Performance

Quote:
Originally Posted by JRP3 View Post
1238-7601 at 650 amps x 120V = 78KW
The new controller at 500 amps x 160V? = 80KW, not that impressive even if it can actually run at 160V.
That's not how you calculate power for 3-phase AC motors.

use this:
P=√3*V_RMS*A_RMS*cosφ
V_RMS = (Batt_voltage/√2)

But yes the ratio is the same.

Quote:
Originally Posted by JRP3 View Post
I'm not saying the 80KW isn't good, I'm saying that claiming the new Curtis controller, (which might only add 2KW or so), makes a big difference with the AC50 is dubious at best.
Voltage will sag less with 500A if we assume the cells are the same.
So higher voltage @ load = more power.
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  #28  
Old 05-25-2012, 06:27 AM
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Default Re: Curtis 1238, AC 50 Sluggish Performance

Good point about the voltage sag, which will be more or less of an issue depending on the cells used.
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  #29  
Old 05-25-2012, 06:29 AM
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Default Re: Curtis 1238, AC 50 Sluggish Performance

Quote:
Originally Posted by Hippie Djohn View Post
That's not how you calculate power for 3-phase AC motors.

use this:
P=√3*V_RMS*A_RMS*cosφ
V_RMS = (Batt_voltage/√2)
True. But cosφ is typically around 0.82, which is very close to √2 / √3, so the √3 / √2 * cosφ comes to close to unity anyway. So the very convenient Batt_Voltage * A_RMS is a great approximation. There are also the losses of the controller, if you want to get really pedantic; at around 130 VDC, the ~2.0 - 2.5 V drop across each IGBT (and there are two in series) becomes moderately significant. Less so at 160 V, of course, but not by much. [ Edit: as pointed out below, this is actually an argument to use phase voltage and current, not the approximation. ]

Last edited by Coulomb; 05-25-2012 at 05:43 PM.
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  #30  
Old 05-25-2012, 06:41 AM
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Wink Re: Curtis 1238, AC 50 Sluggish Performance

Quote:
Originally Posted by Coulomb View Post
True. But cosφ is typically around 0.82, which is very close to √2 / √3, so the √3 / √2 * cosφ comes to close to unity anyway. So the very convenient Batt_Voltage * A_RMS is a great approximation. There are also the losses of the controller, if you want to get really pedantic; at around 130 VDC, the ~2.0 - 2.5 V drop across each IGBT (and there are two in series) becomes moderately significant. Less so at 160 V, of course, but not by much.
True... but if we are calculating single hp's for the new Curtis it will make a differens ;-)
If the power is calculated direcly from the phase current and voltage, it includes the controller loss.
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