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Old Nov 16, 2011, 04:36 PM
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United States, KY, Louisville
Joined Jul 2008
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What makes an HV ESC, HV?

Just curious as to what it is that causes an esc to be labeled as HV? What internal components change from non-hv to hv esc's? Whats the internal makeup difference in HV vs non-HV ESC's?

Is there a way to convert a non-HV ESC into a HV ESC?

Just started wondering about this and hope someone has an actual answer.
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Last edited by SkylineFlyer; Nov 16, 2011 at 04:47 PM.
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Old Nov 16, 2011, 04:40 PM
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Chattanooga, Tennessee, United States
Joined May 2003
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An HV ESC can cope with high voltage... a typical ESC can only deal with 2s/3s/4s.

Since it would be impossible to find a BEC circuit which could get 50v or 100v down to the 5v needed for Rx and servos, HV ESCs are usually OPTO isolated (no BEC)....... they need to be powered by an external pack or a UBEC
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Old Nov 16, 2011, 04:45 PM
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Quote:
Originally Posted by Dr Kiwi View Post
An HV ESC can cope with high voltage... a typical ESC can only deal with 2s/3s/4s.

DR KIWI, I apologize as my question was worded poorly.


I know what they can handle, but WHAT makes them able to handle it? Is it the capacitors, or is it something more internal within the ESC itself?
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Old Nov 16, 2011, 07:11 PM
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Hastings, New Zealand
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Capacitors, FETs, FET drivers, voltage regulators, diodes etc. all have to be suitably rated.

Low voltage ESC's use 30V rated FETs which are good for 5~6S max, while high voltage ESC's use 55V or 75V rated FETs. Smal ESC's (rated for 30A or less) usually have basic drive circuitry which is only suitable for 3~4S max. ESC's rated for 40A or more often have high voltage drivers that can handle up to 100V, so they are mostly limited by FET ratings. High voltage FETs generally have higher resistance and greater switching losses, so they run hotter and may need better heatsinking.

Very high voltage ESC's also need a special high voltage compliant regulator to power their internal control circuitry (standard voltage regulators can only manage ~35V max.). This is independent of the BEC rating. Some ESC's can be rated for higher voltage if the BEC is disabled or not present, because their internal regulator can handle more voltage than the BEC regulator.
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Old Nov 16, 2011, 07:50 PM
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Quote:
Originally Posted by Bruce Abbott View Post
Capacitors, FETs, FET drivers, voltage regulators, diodes etc. all have to be suitably rated.

Low voltage ESC's use 30V rated FETs which are good for 5~6S max, while high voltage ESC's use 55V or 75V rated FETs. Smal ESC's (rated for 30A or less) usually have basic drive circuitry which is only suitable for 3~4S max. ESC's rated for 40A or more often have high voltage drivers that can handle up to 100V, so they are mostly limited by FET ratings. High voltage FETs generally have higher resistance and greater switching losses, so they run hotter and may need better heatsinking.

Very high voltage ESC's also need a special high voltage compliant regulator to power their internal control circuitry (standard voltage regulators can only manage ~35V max.). This is independent of the BEC rating. Some ESC's can be rated for higher voltage if the BEC is disabled or not present, because their internal regulator can handle more voltage than the BEC regulator.
Bruce, thank you! I never knew it would be a complete remodel of the low voltage ESC's.

I've seen many different cell count esc's. From 20-30A 3-4 cell esc's. 50A 3-4 cell esc's. 60A 3-5cell esc's and a very very strange 80A 3-7 cell esc.
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Old Nov 16, 2011, 08:15 PM
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Des Moines IA
Joined Dec 2005
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Quote:
Originally Posted by Dr Kiwi View Post
An HV ESC can cope with high voltage... a typical ESC can only deal with 2s/3s/4s.

Since it would be impossible to find a BEC circuit which could get 50v or 100v down to the 5v needed for Rx and servos, HV ESCs are usually OPTO isolated (no BEC)....... they need to be powered by an external pack or a UBEC
Except the ICE line from Castle up to 8cells
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Old Nov 16, 2011, 10:31 PM
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As Bruce indicated, FETs have several standard voltage ratings, 30 volts, 55 volts, etc. The higher voltage FETs have more resistance and cost more so the cost goes up pretty fast. Above 50 or 75 volts it is usually better to use IGBT devices instead of FETs. IGBTs can go up to 1200 volts and 1200 amps.

FETs have a problem that they self destruct when taken to break down voltage. The normal failure mode is to short and cause fire. All bi-polar devices such as transistors have a break down voltage but they only go into a zener mode. The voltage does not cause a failure but the excessive heat causes the failure. So for FETs the voltage causes the failure, for bi-polar devices the heat causes the failure, big difference. Note that zener diodes operate at break down voltage, actually any diode can be run as a zener diode.

Also there is a safety issue, above 48 volts is considered deadly so most hobby manufactures do not want to get into all the problems with high voltage.
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