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- Nov 2, 2012
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I decided to apply full voltage to one of my two MOT's today and noticed that above 80 volts, I could feel the variac dial vibrating as I adjusted the setting. Clearly at that point, the current draw begins to ramp up substantially. I decided to measure and record the idle current at various input voltages. I figured it would be interesting to know, if nothing else.
The MOT in question is a Zebra TAN-100TT. It is rated for 120V and 60Hz input.
The data on the label is:
The "Variac" column is the variac dial setting. The V2 column is the actual output voltage. The IMOT is the MOT idle current for that voltage. I decided to end the test at the 120V setting because going farther would probably damage the variac. Readings were taken every 5 volts according to the variac dial. The current numbers for 125 to 135 were extrapolated from the data, but the voltage numbers were measured on the variac.
It looks like the transformer begins to saturate above 80 volts actual, and is well into saturation by 110 volts. I think if I were to wire the primaries of two of these MOTs in series, saturation would be more or less avoided since each unit would only be seeing 60 volts or so.
I'll do another test like this later, using the Basler Electric MOT that I harvested from a very old (30+ years) microwave that was being thrown out. It should be interesting to see the difference between then and now, because that old MOT is a lot bigger and heavier!
ETA: Btw, formatting that table was a bit of a pain because the forum ignores repeated normal spaces. I had to use U+2004 spaces to make it work but it still looks a bit choppy. I can see why DTR just posts photos when doing his diode current tests. Is there a better way to format a table like this?
Data for Zebra TAN-100TT
Variac V2, V IMOT, A
------- ------ ------
0 0.60 0.00
5 6.18 0.08
10 11.45 0.12
15 17.03 0.17
20 22.0 0.20
25 27.2 0.23
30 32.7 0.26
35 37.7 0.30
40 42.8 0.33
45 48.5 0.37
50 53.5 0.41
55 59.3 0.46
60 64.4 0.51
65 69.5 0.57
70 75.2 0.64
75 80.1 0.72
80 85.6 0.83
85 91.0 1.01
90 96.3 1.26
95 101.4 1.66
100 106.7 2.34
105 111.8 3.23
110 117.2 4.54
115 122.2 6.14
120 126.7 7.69
125 132.3 9.3
130 137.4 10.9
135 143.0 12.5
The MOT in question is a Zebra TAN-100TT. It is rated for 120V and 60Hz input.
The data on the label is:
The variac is a brand-name Variac rated for 115 volts input, maximum current 5A. The actual mains input is 124 volts.MOT label data said:
The "Variac" column is the variac dial setting. The V2 column is the actual output voltage. The IMOT is the MOT idle current for that voltage. I decided to end the test at the 120V setting because going farther would probably damage the variac. Readings were taken every 5 volts according to the variac dial. The current numbers for 125 to 135 were extrapolated from the data, but the voltage numbers were measured on the variac.
It looks like the transformer begins to saturate above 80 volts actual, and is well into saturation by 110 volts. I think if I were to wire the primaries of two of these MOTs in series, saturation would be more or less avoided since each unit would only be seeing 60 volts or so.
I'll do another test like this later, using the Basler Electric MOT that I harvested from a very old (30+ years) microwave that was being thrown out. It should be interesting to see the difference between then and now, because that old MOT is a lot bigger and heavier!
ETA: Btw, formatting that table was a bit of a pain because the forum ignores repeated normal spaces. I had to use U+2004 spaces to make it work but it still looks a bit choppy. I can see why DTR just posts photos when doing his diode current tests. Is there a better way to format a table like this?
Data for Zebra TAN-100TT
Variac V2, V IMOT, A
------- ------ ------
0 0.60 0.00
5 6.18 0.08
10 11.45 0.12
15 17.03 0.17
20 22.0 0.20
25 27.2 0.23
30 32.7 0.26
35 37.7 0.30
40 42.8 0.33
45 48.5 0.37
50 53.5 0.41
55 59.3 0.46
60 64.4 0.51
65 69.5 0.57
70 75.2 0.64
75 80.1 0.72
80 85.6 0.83
85 91.0 1.01
90 96.3 1.26
95 101.4 1.66
100 106.7 2.34
105 111.8 3.23
110 117.2 4.54
115 122.2 6.14
120 126.7 7.69
125 132.3 9.3
130 137.4 10.9
135 143.0 12.5
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